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Annexure – B
VOLUME - II
TECHNO-COMMERCIAL SPECIFICATION FOR TENDER ENQUIRY FOR
SUPPLY OF PLANT & MACHINERY FOR PRODUCTION OF COMBUSTIBLE
CARTRIDGE CASE COMPONENTS INCLUDING ASSOCIATED CIVIL WORKS AT
O.F. NALANDA PROJECT AT RAJGIR, BIHAR, INDIA
Specification No. – SPCN/III/2016/OFN/BMCS
REQUIREMENT
COMBUSTIBLE CARTRIDGE CASE MANUFACTURING PLANT WITH A CAPACITY OF
400000 MODULES /ANNUM (100000 MODULES / ANNUM M -91 AND 300000 MODULES /
ANNUM M - 92) WITH THE FACILITY TO AUGMENT ADDING INCREMENTAL UNITS FOR
INCREASING CAPACITY IN FUTURE.
ALONGWITH ASSOCIATED CIVIL WORKS FOR TECHNOLOGICAL BUILDINGS AND UTILITIES FOR
ALL THE PLANTS.
STRUCTURE OF THE TENDER DOCUMENTS
VOLUME ANNEXURE No. SUBJECT SHEETS
VOL II Annexure XV (General) STEC Pamphlet No. 1 10
Annexure XVI (General) STEC Pamphlet No. 3 33
Annexure XVII (General) STEC Pamphlet No. 6 6
Annexure XVIII (General) STEC Pamphlet No. 7 41
Annexure XIX (General) STEC Pamphlet No. 8 18
Annexure XX (General) STEC Pamphlet No. 17 15
SECTION – I
INTRODUCTION
Scope 1. This pamphlet covers guidelines on the technical requirements for design and
construction of explosives storehouses (which include magazines), process buildings
(which include ammunition break-down workshops, laboratories, etc.) and traverses
2. While planning explosives facilities, the lay-out, orientation, design and construction of
the buildings and traverses should be such so as to meet the following requirements:
(a) At an Exposed Site (ES) initiation of, and/or damage to the contents of an Explosives
building, can be prevented/minimized by structural resistance to blast, high velocity
missiles and flame.
(b) At a Potential Explosion Site (PES) initiation of and damage to, the contents of adjacent
buildings can be prevented by intercepting high velocity missiles and reducing blast.
(c) In process buildings, personnel can be protected from the effects of a nearby explosion.
3. The prescriptions contained herein reflect only the special features and therefore must be
read in conjunction with the latest engineering practices along with the general
specifications stated in these regulations.
4. Users are to interpret these regulations intelligently, bearing in mind that these
regulations, although comprehensive and exacting cannot be expected to provide for
every contingency or emergency that may arise, or to replace sound judgment, common
sense, and efficient supervision. However, in case of any doubt, the matter can be
referred to CFEES, Brig S.K. Mazumdar Marg, Timarpur, Delhi for clarification.
Definitions
5. Definitions of various terms used in this pamphlet are given in “Quantity Distances
Regulations for Military Explosives – STEC Pamphlet No.1”. Meanings of a few other
expressions occurring in this publication are given below:-
(a) Magazine- A magazine is an explosives storage building where observance of clean
conditions is necessary, construction of which embodies certain special features and
intended primarily for the storage of UN Hazard Division.1.1 explosives relatively more
sensitive to spark and friction. Such special requirements are enumerated below:
(i) Floor must be gritless, even smooth and free from cracks.
(ii) The interior faces of the walls be vertical, even, smooth and free from cracks.
Ceiling, pillars, wooden fittings and interior wall surfaces must be painted with
adequate coats of approved magazine paints conforming to relevant JSS/IS/IND/ME
specifications. In all buildings, expense stores/transit buildings, 7
magazines and process buildings where CE or nitrophenolic bodies are
handled/stored, the paints used as internal finish should be of lead-free type
conforming to relevant IND/ME specifications and for other buildings, it should be of
lead-restricted type conforming of IND/ME specifications.
(iii) All the internal corners of the floor, walls and roof must be rounded off to prevent
accumulation of dust.
(iv) Exposed iron/steel must be avoided.
(v) There is no restriction on the use of aluminium or aluminium alloys containing more
than 1% of magnesium for permanent fixtures like doors, etc.
(vi) Where wood has to be used for doors, windows, etc., it should be covered with
asbestos cement sheet or other fire resisting materials, e.g., paints conforming to
relevant JSS/IS/IND/ME specifications.
(b) Explosives Storehouse- A building used for storage of explosives other than those
requiring magazine mentioned at sub para (a) above.
(c) Underground Storage- A building, entirely below the natural ground level and
completely covered by earth.
(d) Above ground Storage- Above ground storage building other than at sub para (a) below
with its plinth level above the ground level.
(e) Bunker type Storage- An above ground type of storage building completely covered by
earth (on all sides and roof) except at the cut-through passage.
(f) Exposed Site (ES) – A magazine, explosive storehouse, cell, stack, truck or trailer loaded
with ammunition, explosives workshops, inhabited buildings, assembly place or public
traffic route which is exposed to the effect of an explosion ( or fire) at the Potential
Explosion Site (PES) under consideration.
(g) Potential Explosion Site (PES) – A building which contains or intended to contain
ammunition and/or explosives under consideration.
Siting of Buildings
6. Selection of the site for the construction of explosives building must be done with due
care taking into consideration the following:
(a) The site should not be susceptible to erosion.
(b) The site should be free from underwater courses.
(c) The site should be well drained and not prone to flooding.
(d) Site with continuous rock strata should not be elected because of the possible
transmission of shock waves to excessive distances.
(e) The site should be within the easy reach of railways, main roads, public transportation,
and sources of labour and supplies of water, fuel and electricity.
SECTION-II
CLASSIFICATION AND DESIGN CRITERIA FOR
EXPLOSIVES STORE HOUSES
Types of Explosives Store Houses/Magazines
7. Depending on the type of explosives and other specific requirements, explosives
storehouses/magazines can be divided into the following categories:
(a) Explosives storehouses/magazines for UN Hazard Division 1.1 explosives.
The building walls for this type of explosives storehouses/magazines shall be of 34 cm
thick brick and provided with a natural angle traverse.
(b) Explosives storehouses for UN Hazard Division 1.2 explosives.
This type of storehouse shall have building walls of 68 cm brick or 45 cm RCC.
Explosives storehouses with the above stipulation of wall thickness are considered to be
effectively traversed against missiles emanating from an explosion in an adjacent
building or stack and therefore as an ES it does not normally require a receptor traverse
as the walls fulfill this function. This type of building may trap some or all of the high
velocity missiles, but however, it leads to increased amount of debris by the very nature
of its construction.
(c) Explosives storehouses/magazines for UN Hazard Division 1.3 explosives.
Explosives storehouses/magazines for Hazard Division 1.3 explosives, i.e., explosives
involving a mass fire risk shall be constructed with building walls of 68 cm brick. A
special feature of this type of building is that it should incorporate a relatively weak
section in the wall or roof to permit the rapid release of internal pressure built up in the
event of a fire. The unit mass of this weak section should be as low as practicable, but in
any case should not be much greater than 50 kg/m2. Typical materials for an end or side
wall of such a weak section could be glass reinforced plastic, asbestos sheeting, shatter
proof glass or special type of light weight laminate materials. Weak section of two
adjacent building should not be facing each other unless the separation distances are
sufficient to prevent propagation of fire by directional projection of burning Hazard
Division 1.3 explosives. The weak section will not be able to resist the high velocity
debris emanating from an untraversed PES containing Hazard Division 1.2 explosives. It
is, therefore, essential that such a weak section should be protected with a 68 cm brick
wall, located at 1 to 1.5 meter distance in front, to act as a good interceptor/receptor
traverse. The length of the wall should be such that it extends at least 1 m on either side
of the weak section. No additional traversing is required.
(d) Explosives storehouses for UN Hazard Division 1.4 explosives. Explosive storehouses
meant for the storage of Hazard Division 1.4 explosives shall have 34 cm brick walls
and need not be provided with a traverse.
(e) Bunker type storages
This category includes any above ground structure which has a minimum of 60 cm of
earth on the roof, with walls backed with earth. This type of storehouse shall have an
inner wall of RCC 22.5 cm thick and an outer wall of 22.5 cm brick with 1.25 cm water
proofing material in between the two walls. This type of storage provided a good amount
of protection as an ES as well as a PES and it is recommended for the storage of Hazard
Division 1.1 and special category strategic explosives. Bunker type buildings should
preferably be constructed near forward line for strategic reasons and in hot and dry
climatic regions to provide a more uniform lower temperature inside.
(f) Igloo (Box type)
Igloo is an above ground, earth covered magazine made of reinforced concrete or steel.
Igloo storage can provide considerable saving in land requirement and also ensure safety
of explosive stocks in adjacent building due to special design features like directional
attenuation of blast. Inter separation distances between igloos with side to side or rear to
rear orientation should 0.5 Q1/3 (for LRC Igloo) and 0.8 Q1/3 (for RCC Igloo) in place
of 2.4 Q1/3 and for constructional details, refer to ENC drawing for RCC Igloo and to
STEC pamphlet No.21for LRC Igloo. Due to this special assign feature it can withstand
less seepage problems than bunker type magazines.
(g) Rocket storage buildings
Where rockets are in a potentially propulsive state, the magazine should be of sufficient
strength to resist their thrust. Alternatively, the rockets should be provided with devices
to secure them and thereby eliminate the additional hazard arising from the flight of the
rocket. Magazines which have not been designed to resist potentially propulsive rockets
or which do not provide adequate anchorage points, should be surrounded with a suitable
vertical inner faced traverse.
General Constructional Requirements
8. The main principles to be kept in view in the construction of explosives storehouses and
magazines are given as under:-
(a) The use of flammable materials should be avoided as far as possible and non-
combustible materials must be used for storehouses containing Hazard Division 1.1 and
1.3 explosives.
(b) There should be no exposed iron, steel aluminium or any aluminium alloy in proximity
to unpacked explosives compositions, which are sensitive to spark or friction.
(c) The orientation of the explosive store house should be carefully planned to avoid direct
sun-light falling on any ammunition/explosive package. Advantage of the prevailing
wind direction may also be taken into consideration to facilitate effective ventilation.
(d) The side should be protected from termite attack.
(e) The construction should be suitably water proofed to eliminate any possibility of
seepage.
(f) The plinth level of the building should be well above the general flood level on the area
and foundations should be strong enough to support the super structure. The drainage
system in the area should be efficient.
(g) Materials like brick, concrete, reinforced concrete or any other pulversiable material is
suitable for construction of explosives store houses. Stone may be used for the
construction of walls of traversed storage only.
(h) The following restrictions are necessary in the use of materials like iron, steel and
copper:
(i) Exposed iron/steel must be galvanized or painted with approved paint.
(ii) Steel over head rails, if required, may be installed without galvanizing or painting
provided the moving wheels are made of non-ferrous metal.
(iii) In buildings which may be used for storage of ammonium nitrate or ammonium
nitrate based explosives, copper and copper alloys must not be used.
(iv) Untraversed explosive buildings shall be provided with 5 meter wide hard-standing
to serve as fire-brake.
Floor
9. The floor should be of well finished concrete free from cracks and crevices. It should be
treated with sodium silicate and must be strong enough to support a load of 10 tonnes
per square metre. Load bearing capacity for process buildings depend upon the type of
stores handled and the requirements of users. These can be designed to withstand 2.5
t/m2 and 5t/m2 respectively. When the floor is cast in panels, the joints must be
carefully prepared to achieve a smooth finish and to avoid chipping. While casting floor
panels, metal strips should be used in lieu of glass strips. The floors, for certain building
when require, shall be surfaced with an approved composition, which is both spark-proof
and capable of disseminating static electricity as per STEC Pamphlet No.7.
Walls
10. The specifications of walls for different types of explosives store houses have been
described in para 7. The interior surface of the wall should be finished off smoothly and
free from cracks and crevices. Wall may be painted, glazed or treated with a good oil
bound distemper of approved type. Plastering/grinding is acceptable for explosives store
houses.
11. The height of the wall should be such that there will be a clearance of 60 cm between
the top of the explosive stack (which may go upto 3.75m) and the roof height to
facilitate handling of the explosives packages and for providing clearance from the roof.
For this purpose, the reduction in the clearance at the soffits of the beams may be
ignored.
12. In buildings storing air-craft bombs, sea-mines, heavy ammunition packages etc. where
stack heights are low, the building height may be reduced as convenient.
13. In building storing missiles, etc. where crane and other lifting appliances have to be
used, the building height may be increased if required.
Roof
14. The roof for the various types of explosives store houses mentioned in para 7 above
shall be of well rendered RCC construction, minimum 15 cm thick with a suitable slope
on either side and effectively water proofed.
Doors
15. The number of doors, their sizes and disposition may be decided depending upon the
size of the building and actual user requirements. Explosives buildings must however be
provided with at least two doors for use as alternative exits in the event of a fire or
explosion.
16. The doors should open outwards, be fire resistant and made to fit as close as possible.
The doors shall be made of steel suitably painted over with an approved fire resistant
paint and shall be minimum 12mm thick.
17. In case of bunker types storages, two sets of doors are provided with a lobby in
between. The door at the outer end of the lobby is to be of grill/collapsible type.
18. Explosives/ammunition boxes are not to be opened inside the store house and hence to
enable periodical sampling etc. a lobby of suitable size with earth plate for discharge of
static charge may be provided for this purpose. A small room should be provided outside
the building earmarked for drawing the sample and closing the same afterwards before
depositing in the storage building.
Windows
19. Windows or skylights are not to be provided for explosives storages.
Ventilators
20. All explosives buildings shall be fitted with adequate number of ventilators to create
effective ventilation when required. They should be well baffled and fitted with suitable
wire-mesh net to prevent entry of rodents and reptiles. Provision of two sets of vents,
one at about 0.3 m from the floor on one side of the wall and the other set at higher level
near the roof on the opposite wall aid the creation of good draught and should be
adopted. The ventilators should have “hit and miss type” Z vents to secure against forced
entry/sabotage.
Loading Platforms
21. The design of the building should be such so as to meet requirements of rail or road
service or both. Suitable covered loading platform should be provided.
Sizes of Buildings
22. The following general principles should serve as a guide while deciding the dimensions
of storages/explosive houses:
(a) A low or bunker type building is less likely to be affected by blast from an outside
explosion.
(b) Storage building of greater height normally maintains lower and more uniform
temperature and facilitates taller stacks and use of mechanical lifting devices.
(c) When rail service is to be provided, a long building will allow a number of wagons to
be dealt with at one time.
(d) Building with fewer pillars/columns would be most convenient for internal
movement, use of fork-lift trucks and fire fighting and avoids wastage of space.
(e) For working out the storage space requirements for stacking of
explosives/ammunition, the floor area calculations should be based only on 50% of the
available storage space to cater for the clearances from walls to stacks, stack to stack,
passage ways for handling, etc.
23. The sizes of the buildings to be adopted are essentially governed by the requirements of
the users and types of explosives/ammunition required to be stored. The sizes required
may be selected from any one of the following, which have been adopted by the
Services:
(i) 15m x 6m (with one internal partition)
(ii) 18m x 10.5m (without column)
(iii) 18m x 12m
(iv) 18m x 24m
(v) 18m x 36m
(vi) 30m x 15m
(vii) 38m x 12m
Record of Temperature
24. All storage building should be provided with thermometers for regular recording of
minimum and maximum temperatures. Wet and dry bulb thermometers or hygrometers
may also be provided, wherever required.
Electrical Installations
25. Electrical installation in explosives store-houses shall be in accordance with the
provisions of STEC Pamphlet No.7 on the subject.
Fire Fighting
26. Every building containing explosives must be provided with adequate first-aid fire
fighting measures as stipulated in STEC Pamphlet No.6 on the subject.
Lightning Protection
27. Lightning protection should be provided to all building containing explosives in
accordance with the provision mentioned in STEC Pamphlet No.7.
Approach Road
28. Approaches to above ground explosives storages, served by roads should be by means
of individual loop road leading from the main road. In case of rail served storages,
subject to practical working considerations a number of storages may be served by one
spur.
Line Plans
29 Line plans of a few typical aboveground explosives storehouses and bunker type
magazines are given at Appendix 2.
SECTION-III
DESIGN PRINCIPLES FOR PROCESS BUILDINGS
Design Fundamentals
30 In general, process building is a building in which explosives are worked upon or
manufactured. This category also includes facilities like ammunition workshops, pilot
plants, development production units, explosives laboratories, preparation rooms, etc.
The main aim of process building design should be to provide maximum possible
protection to those working therein. When these buildings are to be positioned in or near
a storage area, generally a minimum separation distance of 275 m should be kept.
While planning construction of process buildings, the following aspects should be kept
in view:
(a) The process buildings shall normally be single storied unless necessitated by process
requirements.
(b) Maintain minimum distances to inhabited buildings i.e. outside quantity distances and
between process buildings i.e. Process Inside Quantity Distances, by careful site
planning.
(c) Sub-divide process building into compartments by suitable partitioning walls so that a
low NEC (unit risk) is obtained in each compartment. In such cases a reduced quantity
distance can be used based on the quantity of explosives in each compartment of the
building.
(d) Reduce missiles from the PES by smothering effect of the earth cover or by providing
interceptor or container traversed. For this purpose, missiles should be stored in bunker
type buildings or alternatively in buildings provided with Vertical Inner Faced Traverse.
Constructional Requirements for Explosives/ Ammunition Manufacturing plants
31. Although general requirements and other constructional details described in Section-II
for explosives store-houses are also applicable to explosives process buildings, some of
the specific requirements for these buildings are enumerated below:-
(a) In buildings where explosives belong to Hazard Division 1.1, are manufactured or
handled, the building walls shall be 22.5 cm brick and invariably shielded by a vertical
inner faced traverse. In buildings where upto 68 kg explosives are handled, RCC walls
of adequate thickness depending upon the quantity involved shall form the main building
walls to perform the function of a container traverse (see Table 2, Section V).
(b) In buildings where explosives belonging to Hazard Divisions 1.2, 1.3, and 1,4 are
manufactured or handled, the building walls shall be 34 cm brick. Where explosives
belonging to Hazard Division 1.3 are handled, one of the walls should have a weak
section (refer para 7(c) of Section II). Since these buildings are normally untraversed,
care should be taken at the time of planning that they are sited in such a manner that the
doors, windows and weak sections of one building are not facing those of another
building. Alternatively, if it is practicable, traversed buildings should be interposed
between them.
(c) The roof of all the process buildings shall be 15 cm RCC. However in explosives
manufacturing units, specially the nitrating units, where chances of accidents during the
process are relatively high the roof should be of light construction if the quantity
involved is more than 50 kg.
(d) Process building shall be provided with adequate number of exits for quick escape of the
personnel from the buildings in the event of a mishap. Minimum 2 doors are to be
provided to each process room. The doors should be of wood painted with a suitable fire
resistant paint and they should open outwards
(e) Untraversed explosive building shall be provided with 5 meter hard-standing to serve as
fire-brake.
(f) The number and size of windows as well as ventilators should be decided depending
upon the actual requirements. The window and ventilator frames may be of steel or
wood painted with approved type of paint. The glass panes for the windows and
ventilators should be of wired glass type.
Dividing / Partition Walls within Buildings
32. When a process building intended for Hazard Division 1.1 explosives comprises of
several individual rooms/compartments, the partitioning walls should be such so as to
delay substantially, transmission of explosion between explosives on opposite sides of
the wall thereby preventing simultaneous detonation. The main advantage of such
partitioning walls is that quantity distances can then be based on Net Explosive Content
in one compartment (unit-risk) instead of the aggregate quantity in the building. A
second advantage is that an accidental explosion is less likely to render unserviceable all
the stocks in the building. The specification of such a wall depends upon quantity,
proximity and type of ammunition or explosives on each side. The thickness of ECC
partition walls for different quantities of explosives are given below in Table 1.
TABLE- 1
________________________________________________________________________
Wt of Explosives in kg Thickness of the wall in cm for percentage
of reinforcement by volume
Over Upto 0.2% 0.5% 0.7%
0 50 10 10 10
50 75 10 10 10
75 100 15 15 10
100 150 20 20 15
150 200 25 25 20
200 250 30 25 25
250 300 30 30 25
30 350 35 35 30
350 400 - - 30
400 450 - - 35
450 500 - - 35
____________________________________________________________________
Notes: (a) The explosives will be kept at a minimum distance of 1 m from the wall
(b) The thicknesses given above do not ensure the protection of machinery and other
equipment.
(c) The wall if made of brick should be twice thickness of RCC wall with 0.2%
reinforcement.
(d) In case of Hazard Division 1.2 and 1.4 explosives, the partition wall, carried
from floor to roof without any gap, should be constructed of 23 cm thick brick.
(e) In case of HD 1.3 explosives, design of multiple compartment storage building
upto 10 ton per cubicle capacity, should have the following design parameters:-
(i) Side, rear and partition walls should be of 30 cm thick RCC
(ii) Front wall should be of 20 cm thick brick.
(iii)Door should of 6mm thick MS sheet welded in angle iron same of dimensions
60mm x 60mm x 6mm thick.
(iv)All bays should have independent 10 cm thick RCC roof.
(v)For calculating of size of the cubicle, a criteria of 10m3/t of propellant should
be used.
(vi) Since the front portion of such a propellant storage magazine acts as a
pressure release and flame, siting with front to front orientation of building
should be avoided.
(vii) From such a potential explosives site, the quantity distances to exposed site
should be used in maximum quantity of propellant stored in any of the
cubicle.
Ammunition Workshops, Pilot Plants, Development Production Units, etc
33. The constructional and other special features mentioned in paras 31 and 32 above for
explosive / ammunition manufacturing plants are also applicable in the design and
construction of ammunition workshop, pilot plant, development & production unit and
ammunition preparation room. Depending on the actual user requirement, these
prescriptions may be suitably altered, particularly for specialized buildings like missile
test rooms.
SECTION-IV
CODE OF PRACTICE FOR EXPLOSIVES LABORATORIES
General Principles
34. Explosives laboratories under R&D and DGQA Organisations handle explosives in
small quantities. These laboratories may some time handle and deal with such type of
explosives whose properties are not fully known or established. Utmost care and all
possible safety precautions must be taken for safeguarding personnel and property while
planning and setting up of explosives laboratories
35. The main principles to be kept in view while deciding the lay out, design and
construction of new facilities are:-
(a) Explosives laboratories should be a single storey construction as far as possible.
(b) These laboratories should be sited preferably outside the enclosed explosives area;
however, if due to functional requirements this is impracticable then they must be
located beyond process inside quantity distance or 45 m from an explosives building,
whichever is more.
(c) Construction should be such as to preclude the communication of effects of explosion of
fire in case of a mishap, to the adjoining laboratory/rooms.
(d) Reduction of explosion and fire risk to the minimum th9is necessitates the elimination
of as far as possible, flammable materials from the structures.
(e) Provision of adequate entrances and exists so that in the event of an accident the
operators quickly escape from the building without any hindrance.
(f) Provision of efficient working conditions- There must be no overcrowding by men or
plant, machinery, stores or apparatus in explosives rooms.
(g) The area shall be enclosed by proper perimeter fencing for security reasons.
36. The prescriptions contained herein are to be followed in the planning of new explosives
laboratories. It is not intended that extensive alterations be made to the existing
laboratories to make them conform to these regulations. However, if it is practicable and
economically feasible, necessary modifications may be made to bring them up to the
desired safety standards.
Salient Constructional Features of Laboratories
37. The main laboratory building should comprise of several laboratory room to permit
process activities of compatible explosives only to be carried out in each laboratory
room. Users may suitably alter this set up depending on their actual functional
requirements.
38. The building plinth should be sufficiently raised so as to prevent any water entering it.
The apron around it should be sloping outward to drain the surface water.
39. The construction of laboratories should be of most economical materials consistent with
stability and climatic conditions. Brick, concrete and stone are the most suitable. Wood
and flammable material generally should be avoided. As far as possible doors, windows
and ventilators should be of steel.
40. The floor should be non-slippery and of well finished concrete free from cracks and
crevices. In laboratory room/s where highly sensitive compositions are handled, the
floors shall be surfaced with an approved composition/material which is both spark
proof and capable of disseminating static electricity.
41. The main building walls including the partitioning walls of individual laboratory rooms
shall be 34 cm thick brick. Inside surface of walls shall be finished off smoothly and free
from cracks and crevices. Walls may be painted, glazed or treated with a good oil-bound
distemper.
42. The roof shall be of well-rendered RCC construction of minimum 12.5 cm thickness to
give protection against penetration by debris, low velocity fragments and lobbed
ammunition.
43. Adequate number of windows, doors and ventilators shall be provided in the
laboratories. It is desirable to have minimum number of two doors per laboratory room.
Windows and ventilators shall be fitted with wired glass panes.
Explosives Limits
44. (a) Laboratory Rooms
Maximum permissible explosives limits of different laboratory rooms shall be as under:
High Explosives/Ammunition Laboratory : 2.5 kg
Propellant Laboratory : 5.0 kg
Initiatory Laboratory : 0.1 kg
Pyrotechnic Laboratory : 1.0 kg
It is desirable that an initiatory laboratory be provided with a cubicle having pigeon
holes properly earthed for the storage of initiatory samples upto a maximum limit of
0.25 kg.
(b) Sub-Storage/sample cubicles
To cater for daily requirements/supply of explosives to the various laboratories, a
separate building having several cubicles for storage of small quantities of explosives
shall be constructed at a minimum of 5 m distance from the main explosives laboratory
building. Construction details as mentioned above will be followed. Maximum
permissible explosives limits i.e. Net Explosive Content (NEC) of the various cubicles
shall be as under:-
High Explosives (Hazard Division 1.1) 5.0 kg
Gun Powder and Pyrotechnics (‟‟ ‟‟ 1.1) 5.0 kg
Propellants (‟‟ ‟‟ 1.1) 5.0 kg
Propellants (‟‟ ‟‟ 1.3) 25.0 kg
Ammunition (‟‟ ‟‟ 1.1) 5.0 kg
Ammunition (‟‟ ‟‟ 1.2) 25.0 kg
(c) Laboratories for chemical warfare ammunition, phosphorous and inflammable
liquids/gels.
Laboratories handling chemical warfare ammunition, WP/PWP or WP/ PWP
ammunition, inflammable liquids or gels should be located separately at least 10 m away
from the main laboratory buildings. These laboratories require special first aid
precautions and should be planned accordingly.
(d) Isolation magazines
Waste explosives awaiting disposal should be kept in a separate isolation magazine
constructed at an appropriate distance from the burning ground. Waste explosives should
be kept under oil/water during storage. The isolation magazine should be constructed at
a remote location from the main storage location and quantity distance permitted as per
STEC regulations should be provided.
(e) Burning/Demolition Ground
For disposal of waste explosives by burning, a suitable platform made of fire bricks
should be constructed and for disposal of waste ammunition / explosives by demolition,
suitable demolition pits, as stipulated in AMI Pamphlet OP-IV series should be
provided. The burning / demolition ground should be sighted at appropriate distances, as
given in the above mentioned AMI Pamphlet.
(f) Magazines
For the purpose of storing still larger quantities of explosives/ammunition, magazines
shall be constructed as per the requirements of STEC regulations. Such magazines shall
be sighted at appropriate distances based on quantity of explosives stores.
(g) Sample room to ESH
A small sample room should be provided out side the building earmarked for drawing
the sample and closing the same afterwards, before depositing in the storage building.
45. In an explosive laboratory room or a cubicle meant for storage of explosives/samples,
only explosives which are compatible with each other shall be handled or stored.
However in exceptional circumstances and with the approval of competent authority i.e.
Head of the Establishment, explosives of different compatibility groups can be stored in
a cubicle provided the NEC per cubicle does not exceed 5 kg. Even in such a case,
principle of separating high explosives from primary explosives shall be observed.
46. Explosives of doubtful suitability shall not be stored in cubicles. Arrangements must be
made to have them shifted in isolated magazines and kept under special observation.
Electrical Installations
47. Electrical lighting, heating and power supply in explosives laboratories/ storage cubicles
shall comply with the regulations given in STEC Pamphlet No.7 on the subject. In short,
the following points shall be borne in mind:
(a) An electrical wiring system within an explosive building must be enclosed entirely in
solid drawn/ERW steel screwed conduits. Alternatively lead-covered twin-cored steel
wire armoured cables or mineral insulated metal sheathed cables of approved type
should be used in lieu of conduit system.
(b) Protected electrical lighting fittings in an explosives laboratory shall be in accordance
with the type of explosives handled in that room. Totally enclosed lighting fittings may
be installed in the storage cubicles.
(c) Where necessary, explosives laboratories should be centrally air-conditioned to comply
with the requirements of STEC Pamphlet No.8. In exceptional cases, ceiling fans may be
permitted with suitable safety precautions. Use of pedestal and table fans is prohibited.
(d) Exhaust fans, if installed in explosives laboratories shall be provided with approved type
of electrical motors.
(e) The following heating system may be used in the laboratories:
(i) Hot Water,
(ii) Low pressure steam not exceeding 1 kg/cm2, and
(iii) Thermally-designed electric heaters conforming to flame and explosion
proof standards with a surface temperature not exceeding 85 0C.
When steam or hot water is installed, the temperature of steam pipes or
radiator panels must not exceed 109 0C.
(f) Installation of lightning protection system is not a must.
Fire Fighting and Medical Facility
48. Adequate fire fighting measures shall be provided as per STEC Pamphlet No. 6.
Explosives laboratories should also be provided with medical first aid facilities including
shower bath for immediate decontamination due to spillage of corrosive liquids, etc.
SECTION-V
TRAVERSES THEIR FUNCTIONS AND CONSTRUCTION
Functions
49. A traverse is a solid mass of earth, and, concrete or brick built around a building or
stack containing explosives and its main functions are as under :-
(a) To intercept low-angle high velocity missiles generated by explosion and stop them
from causing direct propagation if explosion/fire to explosive in adjacent buildings or
stacks.
(b) To protect the personnel in nearby buildings/open from low angle high velocity missiles
generated by an explosion.
(c) To protect explosives/ personnel from direct missile attack in the event of an explosion
in an adjacent building containing explosives.
In addition to the above, a traverse also deflects blast/radiant heat even though to a
limited extent.
A traverse, however, provides no protection from high angle missiles fragments of roof,
wall or lobbed ammunition projected upwards. Such missiles/debris, which escape over
the traverses may get scattered over a large area and cause injuries to the personnel in
the vicinity. However, propagation of explosion to the adjacent buildings at Storage
Inside Quantity Distance is unlikely due to comparatively lower velocity of the missiles
falling under gravity, more so if the adjacent buildings have RCC roofs.
Classification of Traverses
50. Traditionally traverses have been classified into three functional types depending on the
nature of protection they afford. It is not always possible to distinguish clearly between
them as they tend to merge according to their position relative to the PES and ES.
However, it is considered that this classification by function is still useful because a
measure of the traverse strength required is indicated. The three types of traverses are as
given below:-
(a) Receptor Traverse – Its function is to protect the explosives within the building it
surrounds from direct attack by low angle high velocity missiles from a nearby
explosion. Normally a building wall of 68 cm brick or 45 cm RCC will serve the
purpose of a receptor traverse.
(b) Interceptor Traverse – It is to protect explosives outside such a traverse from direct
attack by low angle high velocity missiles from an explosion in a building or stack
within its confines. It can be undermined by the crater and destroyed by the blast but it
must remain standing long enough to intercept the missiles. It must be massive to be
effective and hence may be uneconomic for large quantities of explosives.
(c) Container Traverse – Its function is primarily to protect personnel elsewhere from an
explosion within its confines. It must remain substantially intact after an explosion. This
is practicable only for small quantities of explosives upto 1100 kg and may be used for
certain process buildings.
Design of Traverses
51. Depending upon the constructional design, there are six different types of traverses.
They are shown with their explosive limits in Appendix 1. These are as follows:-
(a) Natural Angle Traverse, NAT
(b) Vertical Inner Faced Traverse, VIFT (or Semi Vertical Inner Faced Traverses).
(c) Chilworth type traverse
(d) Bunker type building (or Igloo)
(e) Wall traverse: Brick, reinforced concrete, earth/sand sandwiched between concrete/steel.
(f) Natural features of sit, for example, hillocks, etc.
Geometry of Traverses
52. Proper traverse geometry is necessary to reduce the risk of high velocity projections
escaping above or around the ends of the traverse and so producing an explosion in an
adjacent site. Since such projections do not move along perfectly linear trajectories,
reasonable margins in traverse height and length must be provided beyond the minimum
dimensions, which block the line of sight.
53. In general a traverse should be placed as close as possible to the explosives stack it
protects in order to give maximum shielding from high velocity missiles and also to
restrict its height and length to a minimum. The traverse toe or face should be positioned
about 1 to 1.5 m from the stack of explosives/store house wall. However, it is essential
to make the distance greater to provide passage for vehicles, etc.
54. Earth traverses with a minimum cross-section of 2.5 m at the level of the tope of the
explosive stack are considered to be effective in providing protection. Traverse should
be at least 0.6 m higher than the maximum stacking height of the explosive and, in the
case of a building the traverse should normally be upto eave‟s height. As an alternative
to this, the limiting dimensions for the earth traverses can be controlled by a 20 rule
where the stack height can be fixed. The procedure is to establish a reference point at the
top of the far edge of a stack under consideration (see Appendix 3). The crest width
should be 1 m minimum for NAT and 1.5 m for VIFT. The length of the traverses can be
determined by extending the traverse exclusive of the end slope to 1 m beyond lines
between the extremes of the two stacks of explosives under consideration. These lines
must pass through at least 2.4 m of traverse material (Appendix 3).
55. Where a traverse may be under-mined by the crater or NEC exceeds 70,000 kg, the
traverse should be moved outwards or alternatively the cross section area of the traverse
should be increased in direct proportion to the weight of explosives so that an increase is
made in that part which is normally 2.4 m in cross-section. The stipulation is necessary
to ensure that at least two-third of the traverse based from the crater. The crater diameter
(D) in meters is determined by D=Q1/3 (Q is NEC in kg) and is measured from the
center of explosives.
56. For explosive process building where the explosive are handled/ processed at a height
not more than 1.5 m from the ground level, the traverse may be 0.3m above the
doors/windows height whichever is more.
57. The entrances/passage ways for traversed buildings should be suitably designed to
provide the maximum convenience for mode of service i.e. rail and road. These must
also be so located as to facilitate quick escape in an emergency. This could be achieved
by doglegged entrance should make at its center is related with its length (L) and the
width of opening (D) by the formula i.e. 2 tan-1/(L/2D). A sketch of the doglegged
entrance is given at the Appendix-5. The orientation of entrances should be such that
fragments from inside the building arising from an explosion are contained and entry of
external fragments is precluded.
Materials and Precautions for Construction of Traverses
58. Earth for traverse and for cover of building should be made of material as prescribed
below:
(a) When concrete or brick is used in conjunction with earth, either of these materials may
be taken as equivalent to 4 times its thickness of earth with regard to ability to stop
fragments. Concrete or brick may be used to support the earth or it may be those parts of
the roof and walls of a building, which intercept the high velocity projections.
(b) There are two types of precautions, which are necessary in the construction of earth
traverses of the earth cover for buildings used for storage and process of explosives and
ammunition. One type relates to the potential hazards to the other ammunition and to
personnel in the event that the material is dispersed by an accidental explosion in the
contained building. The other type relates to the precautions necessary to ensure the
structural integrity of the earth traverse or cover.
(c) There is no need to consider the first type precaution if it can be predicted that the
material would not be dispersed by the postulated explosion. This will be the case if the
traverse is sighted beyond the crater radius.
(d) Where it is possible that the material would be dispersed by an explosion, precautions
should be taken to reduce the hazard of large stones causing initiation by impact upon
ammunition or explosives in adjacent sites The selection of material and its use should
be governed by the following prescriptions which represent a reasonable compromise
between undue hazards and excessive cost of construction:
(i) Do not deliberately use rubble from demolished buildings.
(ii) Ensure that stones larger than 75 mm diameter (about the size of man‟s clenched fist)
are removed during construction. Other deleterious matter should also be eliminated.
(iii) The design slope for a well compacted traverse material should be between 1:1.3 to
1:2 (370 to 260) depending on the proportion of fineness in the earth used.
(e) Regarding the second type of precaution relating to structural integrity, this is applicable
for all types of traverse. For this purpose, the material should be reasonably cohesive and
free from excessive amounts of trash and deleterious organic matter. Compaction and
surface compaction should be provided as necessary to maintain structural integrity and
avoid erosion. Where it is impossible to use a cohesive material, for example, at a site in
sandy desert, the earth work should be finished with a layer of cohesive soil or an
artificial skin. On the other hand, one should avoid solid, wet clay during construction
since this is too cohesive and would result in an excessive debris hazard.
(f) To prevent the erosion of earth from the traverse mounds, toe wall of brick or concrete
of 1 m height, should be provided on both sides of the natural angle traverse and on the
outer side of vertical inner-faced traverse. Additionally to bind the earth on traverse,
suitable turfing should be provided.
Wall Traverses
59. (a) External Wall of Buildings :
(i) A 68 cm brick or 45 cm RCC wall of a building can be considered to act as an
adequate traverse at an ES.
(ii) Where stocks are to be preserved, or personnel protected, the walls of the building
can be designed to resist collapse. Appendix-4 gives approximate thickness of simply
supported or cantilever RCC walls to resist various charge weight exploding in an
adjacent storehouse.
(b) Internal Walls of Building Traverses:
(i) The merit of reducing the over all effect of the contents of an explosives building by
providing walled compartments containing small quantities of explosives has already
been discussed in para 33 of Section-III. The is specially important for process buildings
where the walls may be required to act as container traverses and protect personnel.
Suitable RCC walls for this purpose may be obtained by using Appendix 4.
(ii) For relatively small charges often used in process buildings, the following canti-lever
container traverse of 3 m maximum height and 1 m from the charge may be used as
given below in Table 2.
TABLE –2
------------------------------------------------------------------------------------------------------------
Charge Weight Preferred choice: RCC wall thickness Second Choice:
(Buttressed at 3m centers,0.2% Brick wall
tension reinforcement) thickness
kg mm mm
------------------------------------------------------------------------------------------------------------
2.5 225 340
5 225 340
7 225 450
12 225 570
18 300 -
35 450 -
50 600 -
68 750 -
------------------------------------------------------------------------------------------------------------
(c) Sandwich / Composite Walls
As an alternative to a vertical inner-faced traverse, Sandwich/Composite walls
comprising of two 20 cm RCC walls with 3m sand fill in between can also be used for
process buildings handling upto 1100 kg of UN Haz. Div. 1.1 explosives/ ammunition.
Such walls are also recommended as partitioning walls for bin type buildings for unit
risk of above quantity. Besides offering advantages like very little recurring maintenance
cost, better clean area conditions around the process buildings and security, sandwich
type of construction is well suited for situations where availability of land is a major
constraint. However, the initial cost of sandwich wall is likely to be marginally higher
than a vertical inner-faced traverse.
60. Additional design parameters for storage of WP ammunition
(i) Wall: 2.5 m high, 34 cm thick brick
(ii) Roof: 3m high and 15cm thick RCC with sufficient projections outwards to protect
the stores from direct sunrays and rain.
(iii) Door: The ESH should have at least two doors and they should open outward. The
height of the doors may be same as the height of wall i.e. 2.5 m.
(iv) Water Tank: Water tank of size 1.5 m x 1.5 m x 1.0 m close to each door outside the
building.
(v) Floor: PCC: Suitable wire net for WP shed is to be provided after 2.5 m height of
wall to protect the stores against entry of birds. The sketch of WP shed is given at
Appendix 6. 29 30 31 32 33 34 35
SECTION - I
GENERAL
Introduction
1. Explosives are chemical substances or combination of chemical substances, which by nature are liable to
be initiated by spark, friction and percussion. Once these are involved in a fire, they create sudden and
intense pressure on its surroundings, usually characterised by the evolution of large quantity of heat, sound
and flash. Consequently any fire involving explosives/ammunition might very well lead to disastrous
consequences as a result of mass fire/explosion unless dealt with speedily and effectively. As such
manufacture, processing and storage of explosives in any building is always associated with serious fire
and explosion hazard. Unlike other combustible or flammable substances/liquids, the explosives once
involved in a fire do not give any time for making a „sizeup‟ of the situation and any action needed to avoid
catastrophe must be preplanned and embodied in well laid-down procedures. It may, however, be noted
that all the explosives in use are not of similar characteristics and behaviour. As such with a view to
dealing with fires involving explosives very effectively, knowledge of the behaviour /characteristics of the
different explosives/ammunition when involved in a fire is very much essential. Besides the knowledge on
the behaviour of explosives, knowledge on the application of proper fire-fighting measures in accordance
with the behaviour of the explosives when involved in a fire is also very much essential.
2. An outbreak of fire in the vicinity of explosives, or amongst the explosives themselves, is a potential
source of very great and immediate danger to life and property. The head of an explosives establishment
must, therefore, regard as of the greatest importance his responsibility for ensuring that the fire prevention
and protection measures, specified in the relevant explosives regulations and fresh orders issued from time
to time, are taken and that the organization is such that if a fire occurs it is tackled immediately and
energetically with all available resource. For the purpose of fire fighting the term „explosive establishment
means‟ any building, open air site or underground site where explosives are held.
Responsibilities 3. The responsibilities of those persons present at such a fire are defined as follows:
(a) The Head of an explosives establishment shall mean the senior-most officer-in-charge of the
establishment belonging to Defence Services in which explosives are stored, processed, manufactured,
rectified/modified and handled.
(b) The Head of the establishment is responsible for the general administrative arrangements and for the
proper coordination of all the various emergency services arrangements like communication, medical, etc.
He is responsible at any incident in giving advice to the Officer-in-Charge, Fire Services relative to the
explosives safety aspects of fire-fighting. He would decide in any particular instance whether the fire-
fighting services are to tackle the building or stack on fire and/or to prevent the fire affecting adjacent
buildings or stacks. He would determine the risk involved in any given line of action, and direct the
Officer-in-Charge, Fire Services accordingly.
(c) The Officer-in-Charge, Fire Services is responsible for the actual fire-fighting operations, including the
direction of all fire-fighting personnel and equipment on the objectives selected by the Head of the
establishment, and for the implementation of any advice which he may give.
Planning 4. The Head of the establishment will prepare a plan for fire prevention and fire fighting, to include
efficient arrangements relative to the following:
(a) Initiation of the fire alarm.
(b) Safe evacuation of personnel NOT required for fire-fighting.
(c) Fire-fighting measures.
(d) Rescue of trapped persons to a place of safety and first-aid to the injured, if any.
(e) Adequate identification of all buildings.
(f) Liaison with and assistance from the local fire service authority and civil police.
5. Information which may be necessary or desirable to have immediately available in the event of a fire
emergency, must be prepared and kept up-to-date. In particular, consideration must be given to the
following:-
(a) Line drawings of all complex buildings and those presenting definite fire risks, ensuring that copies are
immediately available for the use of the fire service. These drawings should include the following:-
(i) Location of exits.
(ii) Main control switches or valves for ventilation plant, gases, water and electricity,
(iii) Stair ways,
(iv) Fire-stop doors,
(v) Specialized fixed fire-fighting equipment,
(vi) Emergency lighting,
(vii) Any other information which might be reasonably required in an emergency.
(b) A site plan of the establishment showing the location and identity of each building of explosives in each
fire division, and the layout of the principal service mains, including water, gas, electricity and telephone
services. Copies of this plan are to be kept at strategic points in the establishment i.e. fire station, security
office etc. For security reasons the plan should contain only the minimum information necessary for
effective fire-fighting and in this regard the Official Secret Act and current security regulations must be
observed.
Fire-fighting Measures
6. Fire-fighting measures within an explosives establishment calls for close attention to detail and
coordination of all available means to ensure that an out-break of fire is tackled immediately and efficiently
and brought under control as quickly as possible.
7. These measures may conveniently be sub-divided into following:-
(a) Fire-fighting „first-aid‟ measures.
(b) Establishment measures.
(c) Mutual aid scheme.
(d) Local/ civil authority measures.
These measures are discussed in detail as follows:-
(a) Fire-fighting first-aid measures
(i) These are adequate provisions within a building containing explosives or in the vicinity of an explosives
stack in the open, or underground, of fire-fighting appliances and local fire alarms for operation by those on
the spot. The prompt use of these appliances may be the means of preventing a more serious incident and
all concerned must be trained to be fire conscious and capable of operating the equipment efficiently.
(ii) Guide-lines on the provisions of Fire Protection facilities to explosives buildings are given in STEC
pamphlet No-15. A reference can be made to the same for provision of first-aid fire appliances, their
maintenance and testing, training of personnel, location of static water tanks, hydrant-installation etc.
(iii) In case of Air-Conditioned explosive buildings, special fire prevention and fire protection measures are
required. The air-conditioned ducts should be provided with dampers of fusible link type (metallic or
plastic) actuating at a predetermined temperature.
(iv) Thermocole, being a flammable material, should not be used for false ceiling in Air-Conditioned
explosives buildings. Materials like glass wool, gypsum board etc. can be used in lieu.
(v) In case of explosive vans/ GS vehicles used for transportation of explosives and ammunition, the fire
extinguishers to be used in normal and sub-zero conditions in both crew and cargo compartments are :
(aa) 1x9 litre AFFF based mechanical foam extinguisher
(ab) 2x1.25 kg BCF extinguisher
(vi) Fire fighting equipment for use at high altitude areas and sub-zero climatic conditions are referred to
STEC pamphlet No.15, Para 11.
(b) Establishment measures
(i) Establishment measures comprise of the provision of fire-fighting media and equipment
including adequate supply of water from static tanks and/or pressure mains, fixed fire-fighting
installations, hydrants, hose, mobile fire appliances, adequate supply of foam wherever necessary
i.e. fire engines and trailer pumps, fire extinguishers, self-contained breathing apparatus, an
efficient general fire alarm system, means of communication, protective equipment and clothing
and trained fire-fighting personnel.
(ii) All appliances and equipment are to be maintained in an efficient condition. Practices designed
to test the efficiency of the establishment‟s arrangements should be made at frequent intervals (at
least once in a month). Special attention must be paid to dealing with out-breaks of fire during non-
working hours. The fire-fighting drills should also include reciting of various fire-fighting actions
by the fire-fighting crew.
(iii) Capacity of static water tanks for explosives storage areas should be 225 kl and be positioned at
a distance not less than 100 m and not more than 200 m from the storage magazines. In case of
process areas in the explosives factories and laboratories under different service organizations,
capacity of static water tank could be 110 kl to 220 kl depending on local requirements conditions.
For bomb-dumps of Air Force, tank should be of 110 kl capacity.
(iv) Hydrants for fire-fighting purpose may be provided where adequate pressure and output is
assured. Hydrants may be installed on 150 mm diameter main, branched off to 100 mm in cases
where it is meant to feed a single hydrant. For explosives areas water discharge of 1150 litres per
minute at a head of 30 metres should be available from each hydrant when two hydrants are
operated simultaneously. In case of units engaged in non-explosive activities the requirement of
head is 20 metres. The location of the fire hydrants should be decided in consultation with the Fire
Adviser at the time of planning/siting of the facilities.
(c) Mutual aid scheme
When there are more than one Defence units in a station, the Station Commander, who is responsible for
security against fire in all the Defence units of the station shall formulate a scheme of mutual aid by which
all fire brigades maintained by the various Defence units in the station may be brought together for fighting
a fire, on an alarm being raised by any Defence installation on the outbreak of a fire. The heads of the
different Defence installations must fully co-operate and assist the Station Commander in the successful
working of the scheme.
(d) Local/civil authority measures
These measures are those taken by the local fire authority by providing all normal fire equipment
and appliances in use by them together with trained fire-fighting personnel.
Coordination of Measures
8. The close and efficient coordination of the first three elements (a), (b) and (c) as listed in para 7 above, is
absolutely essential. With regard to the element d above, the local/civil authority measures, it is left to the
discretion of the Station Commander and the Head of an establishment, who may seek the cooperation and
assistance of the local civil authorities, if considered necessary and feasible. In the event of such
cooperation the following instructions will be observed by the Head of an establishment:
(a) The Head of the explosives establishment shall inform the nearest Fire Officer of the local civil
authority of the presence of explosives. He shall be given particulars of the nature of fire which he
and his party shall be required to fight in case of an emergency. The Head of the establishment and
the Fire Officer of the local civil authority, in consultation, shall prepare an agreed plan of fire-
fighting in consultation with the Station Commander who shall coordinate the plan on a station
basis. Agreement shall be reached between the two officers on their respective contribution in
equipment and personnel towards the overall fire-fighting plan and combined exercises arranged
where possible.
(b) Agreement shall be reached on the conditions under which civil authority measures would be
called upon.
(c) To minimize delay, there should be permanent telephone communication between the head of
the establishment and the Fire Officer of the local civil authority, by direct line where possible,
particularly at large establishments.
(d) The control of the fire-fighting operations within an enclosed explosives area, when both, the
Govt. establishments and civilian fire services are operating, shall necessarily be exercised by the
Head of the establishment.
Public safety
9. To ensure public safety, the Head of the establishment shall arrange with the local police on the action to
be taken by the latter when an outbreak of fire occurs. The police shall also be kept informed of any
changes necessitating modification of pre-determined arrangements.
GLOSSARY
Air Termination Network: The part of lightning protection system that is intended to intercept lightning
discharges.
Category ‘A’ buildings: Buildings containing or likely to contain explosives which may produce
flammable vapors but not explosives dust.
Category ‘B’ buildings: Buildings containing or likely to contain exposed explosives or explosives, which
may give rise to explosives dust, but not flammable vapour.
Category ‘C’ buildings: Buildings containing or likely to contain explosives which do not give rise to
flammable vapors or explosives dust.
Down conductor: A conductor which connects the air termination network with the earth termination
network.
Earth Termination Network: The part of the lightning protection system which is intended to discharge
lightning currents into the general mass of earth. All parts below the lowest test joint in a down conductor
are included in this term.
Electro-Explosives Device (EED): A one shot explosives or pyrotechnic device caused to function by the
application of electrical energy.
Flame-proof (Ex d): A type of electrical fitting which will withstand an internal explosion of the
flammable gas or vapour which may enter or which may originate inside the enclosure without suffering
damage and which prevents the transmission of the explosion to the flammable atmosphere surrounding the
enclosure.
Dust-tight: A type of electrical fitting which when used in a dust-laden atmosphere does not permit the
entry of any dust.
Increased Safety (Ex e): A type of electrical fitting in which measures are applied so as to prevent, with a
higher degree of security, the possibility of excessive temperatures and the occurrence of arcs and sparks in
the interior and on the external parts of electrical apparatus which does not produce them in normal service.
Pressurised apparatus (ex p): A type of electrical fitting in which the entry of a surrounding atmosphere
into the enclosure of the electrical fitting is prevented by maintaining, inside the enclosure, a protective gas
at a higher pressure than that of the surrounding atmosphere. The overpressure is maintained either with or
without a continuous flow of protective gas.
Non-Sparking: A type of electrical fitting in which in normal operation, it is not capable of igniting a
surrounding explosives atmosphere and a fault capable of causing ignition is not likely to occur.
Totally enclosed: A type of electrical fitting which is protected by mechanically sound enclosure, weather-
proof and insect-proof without opening for ventilation but not necessarily air-tight.
Floor, antistatic: A floor which is sufficiently electrically conductive to disperse charges of static
electricity, but has sufficient electrical resistance to minimize the danger from electric shock.
Intrinsically safe circuits (Ex ia) -
Referred to flammable gas or vapour: A circuit in which neither spark nor thermal effect produced in the
test condition prescribed in IS:5780-1980 is capable of causing ignition of a given flammable atmosphere.
Referred to explosives: Circuits which, when connected into an explosives train or system normally
initiated by an EED, remain incapable of initiating such a device when the circuit is energized from the
intended power source.
Intrinsically safe electrical apparatus/equipment (Ex ib) -
Referred to flammable gas or vapour: Electrical equipment consisting of an assembly of electrical
components, circuits or parts of circuits usually within a single enclosure in which all the circuits are
intrinsically safe.
Referred to explosives: Electrical equipment when connected into an operated in conjunction with an
explosive train or system normally initiated by an EED, is incapable of causing the device to function.
Type of Protection N: Ex n
Zone of Protection: The zone considered to be protected by a complete air-termination network of an
lightning protection system.
Index of Protection: IP
Refer to the BIS Standards for IP number in glossary.
Quantity Distance (QD): This is the minimum permissible distance to be observed from explosives stocks
to other explosives to prevent direct propagation and to ensure minimum practicable risk to life and
property should an explosion occur.
Storage Inside Quantity Distance (SIQD): This is the minimum permissible distance between any two
stacks / buildings used for storage of explosives inside the enclosed explosives area.
Process Inside Quantity Distance (PIQD): This is the minimum permissible distance to be observed
between an explosives building / stack and process building production line inside the enclosed explosives
area.
Outside Quantity Distance (OQD): This is the minimum permissible distance between an explosives
building / stack to utilities/ places used by the general public outside the enclosed explosives area.
SECTION-1
CATEGORIES OF EXPLOSIVES BUILDINGS
Scope
1. These regulations govern electrical installations in buildings containing military explosives and prescribe
minimum requirements of safety and are applicable to the following areas:-
a) All the explosives and ammunition storage buildings located within or outside an enclosed explosives
area.
b) Explosives and filling factories under Ministry of Defence.
c) Ammunition workshops, explosives laboratories, breakdown laboratories and ammunition proof
establishments under Ministry of Defence.
2. These regulations should be read in conjunction with all the relevant departmental specifications and
codes of practice/specifications listed in Appendix „A‟.
Categories of Buildings and Standards of Installations, Equipment & Apparatus
3. All buildings containing explosives are divided into three categories according to the nature of
explosives which are stored or handled in the building. Electrical installations, equipment & apparatus are
afforded the same category as the building in which they are installed or used:-
a) Category A: This category compresses explosives store-houses, laboratories or process buildings in
which explosives may give rise to flammable vapour in the building but not explosives dust. It is sub-
divided into three zones as per BIS specifications IS: 5572 – 1994 which recognize the different degree of
probabilities with which the explosives concentrations of flammable vapours may arise in terms of both the
frequency of occurrence and probable duration of existence on each occasion. The recommendations on the
type of installation to be provided zone wise are covered in BIS specification IS:5571-1979 and
summarized below:-
(i) Category A, Zone O: Zone in which the flammable atmosphere is continuously present or is present for
long periods. In such situations, no electrical fittings/ equipments should be installed. Zone O areas are
generally encountered in petro-chemical industries. If installation of electrical equipments is considered
absolutely essential, the recommendations laid down in (IS: 5780-1980) should be used. For explosives like
nitro-glycerine which has the property to sublime, it is recommended that either Dust-Tight or pressurised
electrical equipment may be used.
(ii) Category A, Zone 1: Zone in which the flammable atmosphere is likely to occur in normal operation.
Electrical equipment which is certified as flame-proof (FLP) with type of protection„d‟ (IS: 2148-1981) is
recommended. For FLP enclosures of electrical apparatus, gases and vapours are subdivided according to
their Maximum Experimental Safe Gap (MESG) determined by means of an experimental vessel.
Alternatively, for intrinsically safe electrical apparatus, gases and vapours are subdivided according to ratio
of their Minimum Ignition Current (MIC) to that of laboratory methane (IS: 5571-1979). Based on MESG
or MIC ratio, gases/vapours are subdivided into three subdivisions, namely Subdivision „A‟ (Benzene,
toluene, kerosene, ethylacetate, ethanol, etc.) and Subdivision „C‟ (Hydrogen, Acetylene, Carbon
disulphide, etc.) All lighting fittings should be FLP as per specification IS: 2206 (Part 1) – 1984 and IS:
2206 (Part 2) – 1976.
(iii) Category A, Zone 2: Zone in which the flammable atmosphere is not likely to occur in normal
operation and if occurs it will exist only for a short time. Electrical fittings/equipment, which are suitable
for category A Zone 1 are permitted. Alternatively, increased safety fittings equipment with type of
protection „e‟ corresponding to IS: 6381-1972 or non-sparking electrical equipment with type of protection
„n‟ (IS: 8289 – 1976) or non-sparking electrical fittings for Zone 2 corresponding to IS: 8224-1976 can be
used.
b) Category B: This category comprises magazines, laboratories or process buildings in which there may
be exposed explosives or explosives dust but not flammable vapour. It is sub-divided into two zones which
recognize the differing degree of probability of incidence and amounts of dust which may be present.
Electrical fitting equipments used have to comply with the following standards:-
(i) Category B, Zone Z: Zone in which the exposed explosives give rise to an atmosphere of explosive
dust. Electrical equipment which is certified to be Dust-tight corresponding to IS: 110015-1984 is
permitted. The electrical fittings should be Dust-tight corresponding to IS: 4013-1967.
(ii) Category B, Zone Y: Zone in which the incidence and amount of dust produced by the exposed
explosives may be considered insignificant. Dust is accumulative in nature and depends on the frequency
and extent of exposure. For example whilst a single operation may be thought to produce insignificant
quantity of dust, repeated operations may produce significant amount which may accumulate and enter
unprotected enclosures of electrical equipment. In the absence of effective housekeeping standards, Zone Y
area may thus degenerate to Zone Z area. It is therefore recommended that for Zone Y area also, electrical
installations and equipments are to comply with Zone Z specifications.
c) Category C: This category comprises explosives buildings in which the explosives are not exposed and
do not give rise to flammable vapours or explosives dust. For buildings in this category all electrical
installations, equipment and apparatus should comply with requirements, of totally enclosed (TE) electrical
fittings as stipulated in STEC Specification given at Appendix „B‟.
4. Corridors and verandas of category A, B and C buildings could be provided with TE lighting fitting.
5. The standard of electrical equipment of vehicles and mechanical handling equipment should be comply
with the standards specified for the electrical installation in the building in which it is being used (see para
45).
Design Considerations
6. Permanent electrical installations for the purpose of providing lighting, air-conditioning and power
constitute an approved integral feature in the construction of the buildings designed for the manufacture,
filling, assembly and storage of explosives and ammunition. If defective in design, erection or operation of
such installations are liable to constitute serious risks and therefore special considerations must be given to
their design, construction, erection and maintenance. These are given as under:-
a) In all cases, installations must be designed and installed to ensure that any over-heating or sparking
whether in normal use or under fault condition is confined within the approved housing of wiring system
and electrical items concerned.
b) The circuits for all installations must be provided with excess current and earth leakage protection
necessary to isolate the circuit concerned as quickly as possible in the event of a fault developing.
c) There may be restrictions on the use of certain materials in the construction and equipment of buildings
designed to contain explosives. Enquiries should be made from the Service Headquarters concerned before
proceeding with the installation or alteration of electrical equipment in such buildings. As a guide the
restrictions apply to conditions where certain exposed explosives may be found, examples are exclusion of
lead when picrates are exposed and copper where azides may be exposed. In building where ammonium
nitrate is handled, all iron and steel fittings used in the electrical installation must be effectively protected
against corrosion.
Temperature Limitations
7. The surface temperature of any electrical equipment or installation is not to exceed the following limits:-
a) Categories A and B buildings - 1000 C
b) Category C building - 1200 C
Any apparatus or component which may produce excessive temperatures under abnormal conditions of
operation should preferably be fitted with a thermal device to disconnect the appropriate circuit before the
maximum safe temperature is exceeded. In the case of vehicles, lifting appliances and other apparatus, any
portion of which is capable of developing a surface temperature exceeding the limit prescribed above
should be suitably screened to ensure that all exposed surfaces are maintained below these limits.
Approving /Certifying Authority for Different Categories of Installations
8. All electrical installations, equipment and apparatus such as flame-proof (FLP), dust-tight (DT) and totally
enclosed (TE) shall be certified by the Director, Central Mining Research Institute (CMRI), Dhanbad, as
suitable for use in explosives buildings.
SECTION-II
THE SUPPLY OF ELECTRICITY, ITS CONTROL AND WIRING SYSTEMS
Power Supply
9. The electricity supply to the building containing explosives may be either direct or alternating with a voltage
to earth not exceeding 250 volts. On this basis a 500 volts 3 wire D.C. System or a 440 volts 3-phase 50 cycles,
4-wire A.C. system may be employed provided the mid-wire or neutral conductor is connected to earth in
accordance with the Indian Electricity Act and Rules.
Siting of Electrical Distribution Installations
10. The design and siting of the electrical distribution system and buildings in which the equipment is housed,
are to ensure that there is no risk of damage to any building or stacks containing explosives.
a) The generating stations and sub-stations (including mobile and semi- mobile generators) should be
located at PIQD or a minimum distance of 45 meters which ever is more from any building containing
explosives. The purpose is to protect the buildings containing explosives from explosion/fire occurring
within the electrical installations.
b) Low and medium voltage switch houses and feeder pillars are to be sited not less than 10m from any
building containing explosives.
11. If low and medium voltage electrical apparatus is provided with an effective containment (by means of
34cm brick wall or equivalent) relative to the explosives, including overhead containment then the
minimum distances required by sub para 10.a may be reduced to that required by sub para 10.b.
12. If the generating station and sub stations are to be protected from an explosion in the explosives buildings,
these should be sited at process inside quantity distances from the nearest explosive block building. Main
generating stations should preferably be located at outside quantity distance from any explosives building.
13. When in an electrical station or sub station or in switch houses within an enclosed explosives area, fuel oil
in sufficient quantity is held, drains must be provided to lead oil leakage into a single filled sump of an
adequate size to contain all leakage. Further a fire break of at least 2 meters must be maintained around the
sump. This should be observed in addition to the requirements given in IS: 3034-1993.
Distribution
14. Electrical distribution in an area containing explosives may be underground cables or overhead lines. Cables
laid underground are preferred and should be adopted wherever practicable. For maintenance reasons cables
should not be laid below buildings but no other restriction is imposed on their location. All feeder cables
should be paper insulated lead sheathed double steel armoured or PVC insulated similarly armoured and
must terminate outside the buildings. The installation of cables must comply with departmental
specifications and IS: 1255-1983.
15. Where the distribution is by overhead line, the conductors are to run throughout the route and be terminated
at not less than 15m from any building containing explosives, and the remaining distance completed by
underground cable.
16. A surge protective device is to be fitted at the junction of the overhead line and the underground cable
between conductors and earth.
17. The fixing of supports for overhead lines to buildings containing explosives is prohibited. The siting of
poles or other forms of support of overhead lines or street lighting columns should ensure that in the event
of failure of a support of conductor, they cannot fall on a building containing explosives.
18. The requirements of paras 14-17 also apply to fire alarms and telecommunications systems with the added
requirement that fire alarm points and emergency call boxes are not be sited where they are likely to be put
out of action by an explosion in an adjacent building.
Plans of Underground Cables
19. Explosive establishments are to hold upto date plans showing the position and size of all underground
cables, including the location of all joints in cables, cable pits, etc. within the explosive area.
Wiring Systems
20. The electrical systems within buildings and underground sites are to comply with the code of practice for
electrical wiring installations IS: 732-1989.
21. The following wiring systems are permitted in categories A, B and C buildings subject to the specific
requirements given in paras 22 to 24:-
a) Screwed metal conduit systems enclosing PVC cables.
b) Mineral insulated copper aluminium covered cables.
c) PVC insulated multi-cored, wire armoured cables.
d) Paper insulated, lead covered steel wire armoured cables.
Additionally, an approved non-metallic conduit system enclosing PVC cables may be used in Category „C‟
buildings only; i.e. totally enclosed standard
Conduits
22. Metal conduit is to comply with the following requirements:-
a) Metal conduits may be solid drawn/ERW or buttwelded and screwed and are to be galvanized or hot zinc
dipped or stove enameled as a protection from corrosion, conforming to IS : 9537 (Part 1)-1980 for buildings
requiring FLP installation. Welded steel screwed conduits to specification IS: 9537 (Part 2)-1981 may be used
in buildings requiring DT and TE installations.
b) Metal conduit is to be screwed tight into all fittings and apparatus, with the minimum of thread exposed and
is to be visible throughout the installation. Conduit unions only are to be used and running couplers are
prohibited.
c) In categories A and B installations, conduit boxes are to be fixed independently of the conduit and their
fixing holes are to be external to the enclosure.
d) In category B installations, conduit threads are to be sealed with approved material and solid backed distance
saddles only are to be used (Hollow saddles with a stable inert material are considered to be solid saddles).
e) Flexible conduits should not be used in hazardous locations involving gas, vapour, liquid or dust laden
atmosphere, as large quantities of dust are likely to enter the flexible conduits and dust-tight enclosures to which
the flexible conduits obtained with the imported machinery may be permitted during the warranty period only
with periodical cleaning. These are to be duly replaced by approved type after the expiry of warranty period.
23. Non-metallic conduits may be used under the following conditions for category „C‟ installations:-
a) Rigid PVC conduit systems are to comply with IS: 9537 (Part 3)-1983.
b) Approved systems are to be of totally enclosed pattern.
c) Additional protection against mechanical damage is to be enclosed throughout the system.
d) A separate and adequately rated earth conductor is to be enclosed throughout the system.
e) Where slip joints or sliding couplers are used, joints should be made using a suitable adhesive.
f) Non-metallic conduit is not suitable for communicating or alarm system wiring.
Cables
24. Cables used in explosives buildings should meet the following requirements:-
a) In all conduit systems, single strand conductor cables are prohibited. Cables are to be PVC insulated 1100
volts grade and should comply with IS: 694-1990. Minimum cross sectional area of a copper conductor is to be
not less than 1 square millimeter and that of aluminium 1.5 square millimeter.
b) Mineral insulated copper-cover (MICC) cables heavy duty 1100 volts class either bare or with a PVC
oversheath, conforming to IS 1554 (Part 1)-1988 may be used. The use of 1100 volts class cables will, to a large
extent, diminish the need for limitations of use because of low electrical impulse strength. In categories A and B
installations only flame proof, DT unions and glands are to be used. MICC cables are not to be connected
directly to apparatus subject to oscillation or vibration to avoid cracking of the sheath by fatigue of the metal.
c) Multicore PVC insulated, wire armoured and PVC sheathed cables to IS: 694-1990 may be used in situations
where severe condensation is likely to occur. Additional protection against mechanical damage is to be provided
where necessary.
d) Flexible cables can be used where cables leads terminate on the machinery which are in motion or in the state
of vibration with suitable compression glands.
Overhead Power Lines
25. National grid overhead systems and associated network and sub-stations are normally not permitted in or to
pass over an explosives area or buildings and should be sited at a safe distance from the perimeter of such area.
26. Although the breaking of an overhead conductor is a rare occurrence, the distance must be determined to
ensure safety in such an event.
27. The physical safe distance „D‟ may be roughly determined by reference to the length of span „S‟ and the
height of the line insulators on the pylon or supporting structure „H‟ as follows
D = S/2 –H
This assumes that should a break occur in the overhead line, natural coiling of the broken line will occur and
restrict the swing in a direction normal to the line axis to less than half the span distance.
28. The electrical safe distances from the foot of an earthed pylon or the earthed network of a sub station is
determined by the requirement that in the event of maximum short circuit current to earth the potential above
true earth appearing at the explosives area perimeter fence must not exceed 4 volts.
29. Distance between an explosives building and public supply overhead power line operating at 3.3 KV or
above should be public traffic route distance i.e. 2/3 OQD subject to a minimum of 60 meters. However, in
respect of internal power line inside the Defence unit these can be sited at 1/2 OQD at the discretion of Service
HQ. The distance to particularly important line like national super grid line (400KV above) should be 1 to 1.5
times the inhabited building distance subject to a minimum of 120m.
30. In special cases, guard wires should be provided for places where electric wires cross over pathways or pass
close to the explosives buildings.
30A. Crossing of Roads and Railways Wherever possible, the public supply and explosives area distribution overhead power lines should not cross
roads and railways.
Control of Electrical Supply Circuits
31. The supply of electricity to a building or underground site containing explosives is to be controlled by one
or more master switches outside the building or underground sites. Master switches should be in close
proximity to each other, identified and capable of isolating every conductor entering the building or
underground site including the neutral of switches/starters, etc. If installed inside the building, these should
conform to the category of installations. If DT fittings are not available, FLP fittings can be used in lieu.
32. All circuits are to be provided with protection against overload and earth leakage.
33. All final sub-circuits are to be controlled by switches ensuring complete isolation of each conductor from
the supply. Lighting circuits may be controlled by switches within the building or underground site provided
they conform to categories of installations.
34. Where large power supplies are concerned, the provision of remote control sub station feeder switch-gear
may be considered as an alternative to the installation of large external master switches. The remote control
should be of a suitably protected push button or rotary switch type with pilot lamp ON/OFF indication and
should be sited at a clearly visible position outside the building or underground site concerned. In any case
switches shall be provided within a fire proof plant room to isolate every conductor entering all areas or rooms
containing explosives.
35. Over current protection may be given by automatic circuit breakers complying with IS: 3842 (Part 1)-1967.
36. Electrical apparatus located in categories B and C buildings containing explosives but in the immediate
vicinity or in an adjacent and separate plant room should only meet the minimum TE standard.
37. Electrical apparatus adjacent to or within the immediate vicinity of category A building should be flame-
proof if the hazard area extends outside the building, otherwise the apparatus is required to meet the minimum
TE standard.
SECTION-III
ELECTRICAL EQUIPMENT
Lighting Fittings and Fans
38. Lighting fittings should be in accordance with category of installation. Electric lamps may be of the filament
or fluorescent types. Only lamps of approved wattage as shown on the design drawings of an installation are to
be sued. The use of lamps of higher wattage is prohibited. Keys for access to lighting fittings should be held in
the office of the engineer responsible for maintenance of the installation and issued only to personnel authorized
by him. Similarly where keys are used to gain access to parts of a conduit installation these should be retained
in the office of the engineer responsible for maintenance of the installation and issued only to personnel
authorized by him. Before opening any lighting fitting or any part of the conduit system, the circuit serving it
should be isolated from the supply and should remain so until all work has been completed.
39. Where fluorescent or electric discharge lighting is installed, a bimetal thermally operated cut-out device is to
be included in the enclosure containing the choke and other components liable to overheating. The cut-out is to
be set to prevent the temperature of the enclosure exceeding 1000 C in category „A‟ and „B‟ buildings and
exceeding 1200 C in category „C‟ buildings, and is not to be of the automatic resetting type. In the case of new
installations, the control equipment including the choke and ancillary apparatus should be outside the building
wherever reasonably practicable and so make the provision of cut-out unnecessary. Chokes and other ancillaries
if fitted inside the explosive buildings should also be in accordance with the category of installation.
40. Unprotected fans are not to be fitted in explosive buildings where explosive dust and flammable vapours are
present. As an alternative, air-conditioning or forced ventilation may be resorted to in lieu.
Mains operated Portable Equipment
41. Portable mains operated lights with flexible leads are not normally permitted inside buildings containing
explosive and plug sockets must not be provided for such fittings; however, where the used of such lights is
essential they should be supplied at a voltage not exceeding 25 V through a flexible cable in which cores are
collectively screened by a copper earth screen and protected by an outer neoprene sheath. The supply should be
taken from a double wound transformer incorporating an earth screen between primary and secondary windings
or alternatively winding should be mounted on separate limbs. A separate core shall be provided in each cable
and the earth continuity conductor shall be bonded at both ends. Such lights will not be used in magazines.
Battery Operated Portable Equipment
42. Portable flood lights of an approved battery operated type may be used only in category „C‟ buildings.
43. Self contained hand or head lamps and torches may be used in explosives buildings provided they comply
with the following requirements:-
a) For category „A‟ installation all external parts if constructed of aluminium alloy shall be free from frictional
sparking hazard. The same is applicable for category „B‟ and „C‟ installations.
b) Dry batteries are preferred but if wet batteries are used, either lead acid or alkaline, the electrolyte is to be in
gel form an unspillable. It must be established that they do not leak if dropped or otherwise improperly used.
Batteries must not be changed or charged in buildings containing explosives. The type of hand lamps which
may be charged without breaking any seals is to be preferred.
c) In areas where regulations require that non-ferrous tools are to be used, hand lamps and torches must also
comply with this requirement.
d) Every lamp or torch shall be type-tested by the approving/certifying authority depending on the building
category.
44. Lighting systems or equipment containing batteries are not to be left unattended inside explosives buildings.
Battery Operated Vehicles and Lifting Appliances
45. The normal action of lead acid batteries involves the evolution of hydrogen gas and introduces the
possibility of explosion if a concentration of gas occurs in a battery container. The rate of evolution of gas
depends on the ampere hour capacity of the battery and the number of cells. It increases with the age of the
positive plates, the temperature of the electrolyte and its density. Battery containers are, therefore, required to
ventilate so as to ensure that the concentration of hydrogen cannot amount to 4 percent, which is the lower limit
of flammability of a mixture of hydrogen and air. Similar precautions are also necessary with alkaline batteries.
In addition the following design features are recommended:-
a) Traction batteries of the lead acid type in categories A and B installations should have all interconnections
duplicated and solidly burned or welded to guard against the production of sparks in the event of damage.
b) Traction batteries of the alkaline type are permitted with single interconnections with terminal nuts fitted
each cell. All terminal nuts are to be fitted with a locking device.
c) The lids of all battery containers should be lined with a non-flammable non-hygroscopic insulating material.
Means are to be provided for locking the cover in the closed position.
d) When ventilation is essential ventilation lowers or screens for battery enclosures should be so designed as to
avoid restriction of ventilation by external means and also preclude objects from accidentally entering the
from mechanical damage. A plug and socket should be provided to facilitate battery recharging.
e) The battery plug and socket shall be interlocked with a switch to prevent removal and insertion while socket
contacts are live or so secured to prevent removal by unauthorized persons.
f) An emergency main isolator should be provided between each battery and its plug socket connection unless
specific approval in obtained for alternative means of protection. This isolator may serve the purpose or sub-
para „e‟ above.
g) The flexible cable to the battery plug should be VR, PCP or PVC-insulated and served, metal screened and
PCP-sheathed overall. Screening of cables for category „C‟ vehicles may be omitted provided extra mechanical
protection is given to the cable.
h) Double pole wiring should be used throughout.
i) Circuit breakers of approved type should be provided to protect the main and auxiliary power circuits.
j) Cable glands for wiring on flame-proof or dust-tight vehicles should be of the flame-proof type.
k) The metallic enclosures of all electrical equipment should be bonded to the framework of the vehicle.
l) The use of solid state electrical control is preferred. Where control resistances are fitted, they should be
housed in the correct Category enclosures.
m) A safety dead man‟s pedal hand or seat switch should be provided.
46. Batteries are inspected and where necessary tested to determine the rate of hydrogen evolution under
departmental arrangements. Battery containers for category „A‟ installations are to be certified by the certifying
and approving authority-Director CMRI Dhanbad.
47. Battery operated vehicles and lifting appliance are permitted along-side stocks of explosives in the open an
along-side all buildings containing explosives.
48. Certified and approved battery operated vehicles and lifting appliances are permitted inside the explosives
storehouses and laboratories in which work is carried out under “Magazine Conditions” (excepting those
classified for magazine storage), provided no exposed explosives are present whilst the vehicle or lifting
appliances are present.
49. Battery operated vehicle and lifting appliances are not permitted inside buildings where explosives are
stored under Magazine conditions.
Provision of Unprotected Lighting Fittings and Ceiling Fans
50. In case of laboratories where naked flames, muffle furnaces and hot plates are used for analysis and testing
of explosives, provision of ceiling fans and unprotected lighting fittings could be considered on merits.
Likewise requirement of protected electrical fittings and fans for ammunition workshops and certain process
buildings could also be examined and considered on merits.
However, in case of laboratories where no muffle furnaces and naked flames are used normal regulations should
apply.
Exhaust Fans and Motors
51. All equipments, appliances fitted in explosives buildings should conform to category of the building in
which they are installed. Depending upon the particular type of risk i.e. flammable vapour or explosives dust
appropriate motors i.e. FLP, DT or TE should be employed. Modified FLP motors conforming to BIS
specification could be used for category A & B areas where flammable vapours and explosives dust
environment prevail.
Public Telephone/Telegraphic Trunk Lines
52. Public telephone/telegraphic trunk lines should be sited beyond process inside quantity distance from
explosives buildings. Overhead lines serving telephones, fire alarm points or call boxes must not be carried
nearer than 15 metres to a building containing explosives, the remaining distance being completed by
underground cable. All wiring for telephones bells or loud speakers within buildings containing explosives must
be totally enclosed in conduit.
52A. Personal Communication Equipment Personal communication equipment (e.g. Cellular Phones) shall not be taken into explosive buildings. Notices
prohibiting the entry of non-approved Personal Communication Equipment shall be displayed at the entrance(s)
of explosive buildings, or areas.
Alarm System
53. These system must not be installed in buildings containing explosives except with the specific approval of
Service HQ. Where considered necessary provision should be made externally to the building for the complete
isolation of all conductors entering the building.
Telephone/Intercoms and Bells
54. When telephones, bells and intercoms are approved for installation in explosives buildings they must
conform to the category of installation. Where flame-proof and dust tight equipments are required, any
equipment certified as intrinsically safe by Director, CMRI, Dhanbad for use in a flammable concentration of
petroleum vapour can be accepted as an alternative. These equipments can be located on the verandah/lobby of
the explosive buildings.
Loud Speakers
55. When service HQ approves the installation of loud speakers within a building containing explosives
requiring a dust-tight installation, the speech transformer and its connection (if any) must be enclosed in a dust-
tight enclosure provided with a conduit outlet. Where no speech transformer is incorporated the speech coil
circuits and all wiring circuits within the building must be of low impedance (3 to 15 ohms) and dust-tight.
Loud speakers certified by the approving authority (CMRI) as intrinsically safe for use in a flammable
concentration of petroleum vapour may be installed in buildings requiring flame-proof, dust-tight or totally
enclosed installations. For loud speaker circuits, provision must be made outside the explosive storehouse or
explosives area for isolating all wiring passing into the building.
Electrical Heating
56. Electrical heating systems and appliances may be installed in explosives buildings of any category subject to
prior approval of Service HQ. Heating appliances and systems must be rigorously tested to ensure safe working
temperature conditions before acceptance.
57. All heating appliances and systems must be fixed and permanently installed. Portable heaters are not
permissible in buildings containing explosives.
58. Only low temperature heaters are to be used which have a maximum designed surface temperature not
exceeding 1000 C in categories A and B buildings and 1200 C in category C buildings. A thermally operated cut
out of the non-automatic resetting type must be fitted to all heaters and heater banks inside buildings to prevent
the surface temperature exceeding the above limits.
59. In all heating appliances used for heating explosives, an additional thermostatic regulator with a maximum
control temperature limit not exceeding 1000 C is to be fitted. The temperature indicating control knob or wheel
is to be positively locked to the control spindle to avoid setting errors. Duplicate indicator lights are required for
appliances of this type.
60. Air recirculation systems are normally not permitted in categories A and B buildings or in heating
appliances containing exposed explosives. If these are inescapable process requirements, flame traps are to be
fitted to both intake and exhaust ducts and the heater banks are to be so constructed as to prevent propagation of
fire or explosion into the building. Fresh air bleed from an uncontaminated source is to be employed to ensure a
minimum of 2 air changes per hour within the appliances or building.
61. Electrode type boilers which are normally to be located at storage inside quantity distance can be located on
the outer half of the traverse or outside the building or inside the explosives buildings in a separate room/cubicle
with adequate wall thickness and RCC roof.
Tools and Appliances
62. No electrically operated tool is to be used in an explosives building unless approved by the Service
Headquarters.
Electric soldering Iron
62.1 The soldering Iron used for soldering operating in an explosive building should meet the following
stipulations:-
a) Soldering should be carried out only at a designated place, in a separate cubicle, which is away from the bulk
ammunition handled in the bldg. No other work on explosives should be undertaken in the cubicle.
b) Since it is not practicable to restrict the surface temperature, the size and rating of the iron should be as small
as practicable consistent with the task to be carried out.
c) The flexible cable fitted to the iron should comply with the requirements of paragraph 24.d of STEC
Pamphlet No.7 (viz. flexible leads should be with suitable compression glands).
d) Each electric iron should be connected to separate wall mounted socket outlet which will insure complete
isolation. It should be provided with pilot lamp indication.
e) The bench top should be of incombustible material and a suitable fire-proof storage space is to be provided to
accommodate the hot iron.
Hearing Aids
63. Electric hearing aids certified as intrinsically safe in the Hydrogen class may be worn in buildings
containing exposed explosives, subject to the approval of Service HQ. Hearing aids are to be secured against
dropping the properly maintained. The battery is not to be exposed and precautions are to be taken to prevent
the inadvertent opening of its container.
Electronic Equipment
64. The design and manufacturing methods of electronic apparatus and instruments do not generally comply
with the requirements of categories of installations and recourse must be made to pressurization ventilation or
other techniques if they are to be employed in explosives building:-
a) Pressurisation is the process by which ingress of an external flammable atmosphere (Category A) or
explosives dust (category B) into an enclosure is prevented. This is achieved successfully by feeding clean air or
inert gas, with or without dynamic flow into the enclosure at a pressure above that of the surrounding
atmosphere.
b) The pressures involved are usually very low about 3-6 kPa (0.4-0.8 psi) because higher pressures might
affect the light construction materials of electronic enclosures, thus giving rise to distortion and mal-
functioning. Further safety of the system depends upon the continuance of the pressure inside the enclosure.
Pressure monitoring devices should be used, either to cut off the electrical supply to the apparatus or to give an
alarm that a dangerous situation has arisen
Electrical/Electronic Balance 64.1 Electrical balances to be used in an explosives building should meet the following requirements:-
a) The display unit and power supply should be housed in ELP/DT enclosure.
b) All power supplies should be routed through approved type of zener barrier device.
c) All zener barriers should be earthed at a point.
Closed Circuit TV Systems (CCTV) 65. Where closed circuit TV system is required to be provided in explosives buildings of any category to
monitor process operations, it should be of an approved design.
66. The following safety requirements are to be complied with for installation of CCTV system:-
a) The camera is mounted externally to the explosives area with a window provided for viewing the area
required.
b) When the camera is required to be sited in the explosives area it should comply with the appropriate
enclosure standard required or alternatively is pressurized or continuously purged with a clean air giving a small
positive pressure of 3-6 kPa (0.4-0.8 psi).
c) For category A and B installations, camera head together with its remote operated pan and tilt mechanisms,
should be housed inside an enclosure in the from of an hemisphere or any convenient shape or blister of fire and
chemical resistant transparent material.
d) Monitors, control and ancillary equipments are to be sited outside the explosives buildings.
X-ray Equipment
67. X-ray of rocket propellant grains and other shaped explosives charges for defect investigation studies is
carried out as a routine for the quality assurance checks in ordnance factories. Where X-ray equipment is
required for the inspection of ammunition, the following stipulations should be complied with:-
a) Radiography should be confined to category „C‟ areas as a general rule. Where, however, it is essential that
such equipment is used in a higher risk area, advice and approval must be obtained from the appropriate Service
HQ.
b) All control equipment is to be sited outside the explosives buildings.
c) The X-ray head is to be of the industrial type with the appropriate enclosure for the category concerned or
alternatively to be pressurized.
d) Portable X-ray equipment is not general suitable for use in explosives buildings.
Barrier Devices
68. A barrier device has been defined as a unit comprising an electrical network when fitted at the interface
between a safe and a dangerous area, ensures that the energy passing from the safe area to the danger area
cannot exceed a definite value which is known to be safe even if severe faults occur within the safe area.
69. While designing a barrier device, the worst possible fault namely unrestricted application of power mains to
the barrier is taken into consideration. The most common type of barrier device comprises a simple network of
resistors and zener diodes with a fuze. The network is designed to have negligible distortion effect on normal
instrument signal, but if there is a rise in voltage on the barrier input, terminals upto the avalanche voltage of the
zener diodes the diodes become conductive and clamp the voltage to a safe value. The current and the voltage in
the danger area is then determined by the series of resistance of the barrier and the zener potential under the
fault conditions.
70. A fuse is incorporated in the barrier device to protect the zener diodes since an excessive potential across the
input terminals (i.e. on the safe area side) may operate the diodes at powers in excess of their long term rating.
The thermal characteristics of the fuse and the diodes are to be such that regardless of the magnitude of the fault
condition, the fuze ruptures before the diodes are damaged.
71. Barrier device should be mounted in a safe area preferably as close as possible to the dangerous area. Where
this is not possible, the barrier should be mounted in a flame-proof or dust-tight enclosure and the circuits to it
from the safe area should comply with appropriate requirements.
72. It is essential that electrical and physical characteristics and maximum lengths of external cables from the
barrier device to apparatus in the dangerous area shall be specified by the certifying authority when these are
likely to affect the intrinsic safety of any circuit.
73. Particular attention must be paid do the method of earthing barrier devices to avoid adverse effects on the
intrinsic safety of the system.
74. Equipment connected to safe area terminals of the barrier device must not be supplied from or contain a
source of potential exceeding 360 volts peak (250 V r.m.s.) with respect to earth. Mains powered equipment
must be isolated from the mains supply by a double wound transformer, the primary of which is protected by
fuses. This isolating transformer must contain an earthed copper foil screen between primary and secondary
windings.
75. The following precautions should be taken for maintenance and testing:-
a) The cables to the dangerous area must be disconnected from the barrier device before any tests are carried out
on the barrier itself.
b) When wiring within the safe area is subjected to high voltage insulation tests, the barrier unit should be
disconnected at the safe area terminals before the test is begun as such a test may rupture the fuses within the
barrier.
c) An annual test should include examination for signs of corrosion, tightness of terminal connections and
measurement of earth connection resistance (earth loop impedance not to exceed 1 Ohm). If malfunctioning of
the barriers is suspected or they may have been subjected to excessive voltages, then the barriers should be
removed from their mountings and checked according to production tests on the appropriate manufacturer‟s
barrier drawing.
Electro Explosives Devices (EED)
76. Electro-explosives devices (EED) also called an electrically initiated/ignited explosives device (EIED) is
one in which an action is dependent on a fuel ignited by an electrical discharge. EEDs are engine starting
cartridges explosives bolts, rocket motors, hot gas power supplies and parachute ejection cartridges. Also it can
be an electric initiator of explosives contained therein. EEDs are used extensively in weapon systems to activate
control and arming devices and to initiate explosives trains.
77. Spurious initiation of EED is likely in the radio frequency and electromagnetic environment. Induced
voltages and currents are set up in the leads of the EEDs under the following conditions:-
Frequency Type of Power Distance Range Modulation Range
HE AM 0.5 to 1 KW 3 m to 1600 m
VHF AM/FM 1.5 W to 50 W 1.5 m to 320 m
A safety factor of 20 decibels below the no fire threshold is safe from electromagnetic hazards for EED.
78. Radio/Radar installations in the vicinity of EEDs should be sited on the following guidelines:-
a) The electrically operated ammunition will not be stored within 45 m of any radio/radar transmitter. In
such situations, all EEDs or ammunition containing EEDs should be adequately shielded against stray
electro-magnetic fields at all times by proper design and packaging. EED or ammunition containing
EED is to be considered fully shielded if they are totally enclosed in metal containers with either
soldered on lids or lids which are tight fittings so as to made good electrical contact with the containers.
Metal skin ammunition into which EED are fitted are considered to be fully shielded provided proper
metal protective covers are fitted over EED. In the same manner EED or ammunition containing EED,
are considered fully screened when they are completely enclosed in metal foil arranged so as to make
good electrical contact all round. The foil must be protected against damage during storage and
handling.
b) Radio and radar transmitter station should not be sited within the OQD of the explosives. If the siting is
an operational necessity the consequent risk of damage should be kept in view. Some protection could
be afforded to the installations within the OQD by providing an effective traverse adjacent to them
where this can be done without interfering with their operations.
c) Mobile VHF and UHF radio sets of power output less than 7 watts may be used outside danger
buildings within explosives areas without restriction.
d) Fixed VHF and UHF radio sets of power output less than 25 watts may be used at ranges down to 8
meters from danger buildings provided:-
i) For explosive devices containing wire bridge fuze heads as initiating components in system
where the stores are not contained in metal containers any exposed firing leads are twisted together,
preferably screened and provided with non-shorting protective covers.
ii) For explosives containing composition type of igniters where the initiating components are
not contained within metal containers or in screened assemblies or where the initiators have to be
handled as separate items their leads are shorted.
79. Conditions for using EEDs and minimum safe distance between radio frequency sources and EEDs are
given at Appendix „C‟. For further details, reference may be made to the STEC Publication “Hazards from
electro-magnetic radiation to ammunition containing Electro-Explosives Devices”.
Air conditioning and Humidity Control
80. Air-conditioning in its true sense, constitutes simultaneous control of temperature humidity, purity and
distribution of air in an enclosed conditioned space. It comprises of basic refrigeration system and air-handling
equipment for circulation of treated air.
81. The installation of air-conditioning in explosives process/storage buildings poses serious hazard as the
control used are electrically operated with electric make and break contacts. During operation the sparking at
the contacts is inevitable and therefore the controls should never be located in flammable dust laden explosives
atmosphere.
82. Location and selection of the proper type of air-conditioning system for used in explosives areas should
ensure safety from inherent fire hazards. Air conditioning plant room or even the weather maker room should,
therefore, not be located inside the air-conditioned explosives buildings.
83. In case of category A and B buildings the air-conditioning system shall be of chilled water type. For
category C buildings this system is preferred over the direct expansion system but is not essential. The plant
room shall be located beyond the traverse or at PIQD in case of the traversed buildings and the weather- maker
room shall be near to or even attached to the conditioned building. When attached the wall separating the
weather- maker room for the explosives building shall be a strong wall of appropriate thickness.
84. In case of category B and C building wherein small quantities of explosives are handled/ stored, the air-
conditioning system could be of direct expansion type. The plant room (including the weather maker room)
could be attached to the conditioned building with an appropriate RCC partition wall in between.
85. When a group of buildings are to be air-conditioned chilled water system shall be used. The plant room shall
be located outside the traverse or at PIQD in case of untraversed buildings. Each building shall be served by its
own weather-maker unit attached to the building itself.
86. In case of building with several bays/rooms to be air-conditioned, safety demands that the individual
bays/rooms to be separately served by the air-conditioned plant to eliminate the risk of fire spreading from one
room to another through the air ducts. Where this is practically not feasible, grouping of bays/rooms could be
resorted to with provisions of automatic fire dampers to prevent propagation of fire through the ducts.
87. Use of room (i.e. window) and package air conditioners is to be normally discouraged. In very exceptional
cases, package type air conditioner housed in a separate room and using air ducts could be provided in case of
category „C‟ buildings, with prior concurrence of STEC.
88. All electrical items like motors, equipments, controls, wiring etc. used inside the weather-maker room
should be of the same category/specification as adopted for the items in the conditioned building.
89. Air-conditioning plant working with ammonia as refrigerant should NOT be used for air-conditioning of
explosives buildings. Use of central type air-conditioning plants working on direct expansion or chilled water
system, instead, is recommended.
90 The blower unit of the air-conditioning plant should be made from non-ferrous material and should not be
belt-driven from the motor to avoid any possibility of static charge generation. Reliable earthing should be
provided.
91. Ducts for supply and return air should be constructed from substantial gauge metal and should be preferably
circular to avoid dust accumulation. These should be straight with least number of bends exposed to view to
facilitate inspection, replacement, etc. All air ducts its insulation, fitments and accessories shall be made from
the non-combustible materials only.
92. Fire dampers should be used inside the air ducts to block the flow of air and prevent fire propagation
through them. Used of automatic fire dampers actuated by a low melting alloy is to be preferred.
93. For humidification purposes, water spray humidifier having pump and spray nozzle combination is
recommended for use with air-conditioning plants. Use of steam and other types of humidification
apparatus/equipment is NOT recommended.
94. Dehumidification by excessive cooling by air-conditioning plants and subsequent reheating of air with hot
water or low pressure steam coils is recommended. Use of electric strip heaters for reheating is discouraged.
Reducing relative humidity by heating alone is not recommended. Chemical dehumidifiers should be critically
examined from safety angle before their installation in explosive buildings.
95. For further details, STEC pamphlet No.8 on Air- conditioning and Humidity Control in Explosives Areas
should be consulted.
SECTION-IV
LIGHTINING PROTECTION, EARTHING AND STATIC ELECTRICITY
Lightning Protection
96. Lightning protection is to be provided for buildings in accordance with IS Code of Practice IS: 3209, 1989.
Lightning protection must be provided for buildings containing explosives where net weight of explosives does
not exceed 250kg for permanent storages and 500kg for temporary storages. Provision of lightning protection
for buildings/open stacks will be in accordance with Govt. of India Ministry of Defence letter No.
95327/STEC/RD-20/III/217/D(R&D) dated 6 Jan 1971 as amended from time to time and a copy of the same is
place at Appendix „D‟. For guidance regarding necessity to provide LP system and selection of appropriate LP
system, reference may be made to the STEC Publication “Protection of Explosive buildings against lightning”.
97. Of the various lightning protection systems in vogue, none can be guaranteed to give immunity from
damage by lightning discharges. The suspended air termination net work is preferable to obtain maximum
protection.
98. The system with a 30-degree zone of protection gives 90 percent probability of immunity from lightning
discharges as against 75 percent probability for the 45 degree zone. The 30 degree figure should therefore be
used for buildings of high risk, i.e. buildings containing explosives sensitive to electrical induction, or thermal
or mechanical shock or where the consequences of an ignition may be very serious.
99. The spacing of horizontal conductors is a matter of judgment according to the risks involved. A spacing of
3m may be considered necessary where a building has penetrable roofs, the explosives store is sensitive to
shock and the consequences of ignition are serious, whereas with a thick reinforced concrete roof on a category
C building containing stable explosives with only a slight or not so serious explosive effect, the maximum
spacing of upto 10m may be permissible.
100. Underground sites and structures may be protected by either an air termination or surface network, but in
all cases it is considered essential that services and major metal work entering the structure should be bonded
together and connected to the lightning protective system at the entrance.
101. The earth terminations of each system are required to be interconnected by a ring conductor which should
be preferably buried. It is permissible, because of the need for bonding other objects to it to leave it exposed on
the wall of the building, but in this case the interconnection is no longer part of the earthing network and will
not form part of the testing of earth termination. The connections to the down conductors on the building which
it interconnects should, therefore, be fixed and permanent.
102. The need to bond metal in and on a building often caused difficulties. In many cases in explosives building
the need for bonding may arise from anti-static considerations rather than from the need only for lightning
protection. The main danger from structural metal in a building which is not part of the lightning protective
system is damage or fire due to side flashing. This can be avoided by isolation, by distance or by bonding. The
need to bond reinforced concrete structures, especially roofs should not normally be in doubt since bonding will
not only prevent rupture or spalling but will give additional protection over its total area. Reinforced concrete
roofs should have connections solidly to the nearest down conductors or roof tapes.
103. Small ventilators, door frames, hinges and similar items may be left unbounded unless they are in close
proximity to down conductors. The bonding of metal window frames in only generally considered essential,
where their configuration can give rise to side flashing that is where their position in relation to roof or down
conductors is such as to offer an alternative earth path for the lightning discharge.
104. Electric supply lines to buildings containing explosives are to be terminated at not less than 15m from the
buildings, the remaining distances being completed by underground cables. This length of 15m underground
cable cannot give protection to the building from lightning discharges carried through the cable from overhead
supply lines due to considerable voltage building up by repeated reflections which need as much as 150m of
underground cable for the originating surge to die off. To overcome this a surge protective device (lightning
arrester) of the appropriate type conforming to IS: 3070 (Part 1), 1985 should be provided at points where
overhead lines leading to explosives buildings are connected to underground service cables.
104A. Making Safe Explosive Facilities
The various precautions are suggested to ensure enhanced safety to personnel working in different explosive
facilities during storms and lightning.
1. Process Facilities:-
a) Stop work.
b) DO NOT deliberately earth explosive assemblies but ensure that they are at least 500mm from the walls of
the facility.
c) Close windows, doors and vents, if possible.
d) Switch off electricity from outside.
e) Evacuate to a safe location.
2. Storage facilities:-
a) Stop work.
b) DO NOT deliberately earth explosive assemblies. Close doors and vents.
c) Switch off electricity from outside.
d) Evacuate to a safe location.
Earthling
105. A common system of earthing and bonding will be employed for all metallic enclosures of electrical wiring
and equipment major metal work in the structure of building and lightning and electro-static protection systems.
The metallic sheath and armouring of the main supply cables metallic pipes including those of compressed air
and steam system rails of guides entering the building will be bonded to the earthing system at the point of entry
or exit outside the structure of the building and will also be earthed at a point 75m away from the building. In
underground installation extra earthing is required at intervals not exceeding 75m along the access roadway or
shaft underground.
106. Earthing of direct current systems shall conform to the following:-
a) The wire systems in which the voltage exceeds 250 volts shall have a point of the system connected
with earth.
b) The connection shall be made at the generating station or sub-station and the insulation of the system
shall be maintained throughout all other parts.
c) The connection shall always be maintained except when it is interrupted by means of a switch link for
the purpose of testing or locating a fault.
d) A fuse or circuit breaker may be inserted in the earth connection in parallel with a resistance of
suitable value to reduce to safe limits any current flowing to earth.
e) An ammeter shall be permanently inserted in the earth connection and the current to earth shall be
recorded daily.
107. Earthing of alternating current systems shall conform to the following:-
a) Any medium or low voltage AC system in which the voltage exceeds 125 volts shall have a point of
the system connected with earth; this means each distinct system from which a supply is given.
b) The connection shall be made at a generating station, sub station or transformer and the insulation of
the system shall be maintained throughout all other parts.
c) The connection shall always be maintained except when it is interrupted by means of a switch or link
for the purpose of testing or locating a fault.
d) No resistance impedance fuse or circuit breaker shall be inserted in the earth connection.
e) The current passing to earth shall be ascertained and recorded quarterly.
f) The point to be connected to earth will generally be the neutral point of the star connected system.
The mid point of one phase of delta connected system may be connected to earth when the working
conditions are suitable. Delta or star connection system, in which the voltage does not exceed 125 volts,
need not be earthed.
108. Safety requirements under short circuit and heavy current fault conditions will normally be met by over-
current protection with fuses or circuit breakers in the main or sub-circuits. In buildings and structures
containing explosives, and especially those having conducting the anti-static floors, it is considered that earth
leakage systems should be employed because of their greater sensitivity in earth fault protection. The type to be
installed, either voltage or current operated, or combination of both, and their position in the circuits, sensitivity
and time of operation must be determined according to the circumstances of the installation.
109. Concerning earth leakage circuit breakers (ELCB) in general, current operated core balance relays with
sensitivity in the range 20/25mA operating at less than 50ms are suitable for most explosives buildings. With
installations where conducting or anti-static floors are used, earth leakage relays with a sensitivity as high as
1.25mA to 5mA operating at less than 100ms have been applied successfully in order to reduce the possibility
of shock on the person handling explosive. Also where direct isolation of particular circuits may be hazardous
undesirable or impracticable such as a firing circuit or a lightning system, the earth leakage really can be
arranged to give a warning only that hazardous conditions has developed.
110. There are three types of electrical systems viz., lightning protection, power and lighting and static which
are provided in an explosives building. These electrical systems are provided with individual systems of
earthing. Common grounding is always desirable as it would equalize the various groundings in or about a
protected structure to minimize the possibilities of a side flash from one grounding system to another.
Combined earthing of LP, lighting, power supply and dissipation of static charges could be permitted depending
upon the actual site conditions.
Static Electricity
111. Adequate precautions must be taken to prevent the accumulation of static electrical charges. Thorough
bonding must be carried out in order to earth all anti-static and conducting materials and all plants and
equipment. Where drive or conveyor belts are fitted they are to be of a material of sufficient conductivity to
assist in draining away static charges.
Electric Spark Sensitive Explosives
112. The classification of initiating and other compositions based a sensitiveness to electric spark and
corresponding degree of precaution in their handling are as under:-
a) COMPARATIVELY If the ignition energy is greater than 0.45 Joule-
INSENSITIVE FIRST DEGREE PRECAUTUONS sufficient.
b) SENSITIVE If the ignition energy is in the range of 0.001 Joule to 0.45 Joule
INTERMEDIATE PRECAUTIONS required.
c) VERY SENSITIVE If the ignition energy is less than 0.001 Joule-
FULL SECOND DEGREE PRECAUTIONS
required.
FIREST DEGREE PRECAUTIONS requires the earthing of all large objects, the use of antistatic conducting
conveyor belts and antistatic or conducting components for pneumatic equipment.
FULL SECOND DEGREE PRECAUTIONS requires the use of floors, conducting bench tops, foot wear and
containers, a minimum relative humidity (normally 65%) and outer clothing not prone to electrification.
INTERMEDIATE PRECAUTIONS As regards intermediate precautions, in addition to first degree precautions,
relaxation of some of the second degree precautions can only be decided upon after consideration of the
properties of the particular composition and the way it is handled. However, some guidelines can be given. For
example, if a composition is ignited at 0.45 Joule and not at 0.045 Joule i.e. it is in the upper energy range of the
intermediate class, then it will be wise to avoid large potential differences on medium sized items of the
equipment. Thus, if material poured from one portable sized container to another, electrical contact between
them and earth should be made before hand. If a composition has an ignition energy greater than 0.001 Joule,
then conducting floors and bench tops will not be necessary. If the ignition energy is in the range of 0.001 Joule
to 0.045 Joule, i.e. in the lower energy range of the intermediate class, then items of highly insulating materials
may be considered but should not be used if they have surface areas greater than 100cm2 e.g. outer garments,
screens and plastic bags. In this energy range, the minimum relative humidity required for second degree
precautions is not necessary, and may not be desirable.
112.1 A warning notice should be displayed on buildings in which anti-static precautions are necessary. A list
of explosives which require maximum anti-static precautions to be taken when they are exposed or handled is
given at Appendix „E‟.
113. The basic difference between conducting and anti-static flooring is its electric resistivity and the
requirements are:-
Conducting grade - Resistance of floor surface to earth must be less than 50 x103 ohms.
Anti-static grade - Resistance of floor surface to earth must be between 50 x 103 and 2 x 106
ohms.
when measured with a wet electrode in accordance with the following method:-
a) The surface of the floor is to be clean and dry. The application of fullers earth followed by wiping with
distilled water is suitable method of cleaning.
b) Tests shall be carried out with an insulation tester having an open circuit voltage of 500 volts D.C. If
explosives are present, an intrinsically safe and certified instrument must be employed. The instrument used
shall not dissipate more than 3 watt in the flooring and the time of test shall not be longer than is necessary for
obtaining a stable reading.
c) The electrode system shall consist of a smooth flat metal foil, a layer of rubber and a weight having an area
of 25cm2. The metal foil shall be of tin or tin on lead approximately 0.025 mm thick and shall be backed by a
layer or rubber approximately 6 mm thick and having a hardness not greater than 60 degree BS. The weight to
rest on the rubber layer is to be approximately 0.91 kg.
d) The floor surface over an area equal to the area of the metal foil shall be wetted with a wetting agent (such as
Teepole or similar detergent). The electrode shall be place on the floor and the electrical resistance measured
between the electrode and known earth connection.
e) Tests are to be carried out between each square metre of the floor and the known earth connection.
114. Installation of conducting and anti-static flooring is to be on a sub floor which should be protected by an
effective damp proof membrane. Bonding strips are to be laid on the sub floor in the form of a grid under the
flooring material. The spacing of the grid shall ensure that at least 2 earth paths are available to each tile or roll
of flooring and the grid shall be connected to the electrical path of the building in 2 positions preferably at
diametrically or diagonally opposite points of the floor. The grid material should either be brass or copper, or
stainless steel of minimum thickness 0.1 mm. Where a non-electrically conducting adhesive is used, great care
is to be taken to prevent the adhesive impairing the conductance between the bonding strips and the
undersurface of the flooring material.
115. Since the first principle of anti-static precaution is to prevent ignition of explosives situations where
maximum antistatic precautions are required conducting flooring should be used. In areas where there may be a
high degree of risk to personnel from electric shock such as research and testing laboratories and missile test
areas it may be desirable to use anti static flooring as an additional precaution to the basic requirements given
above.
116. The use of a personnel test meter for monitoring persons entering buildings fitted with conducting or
antistatic flooring is recommended. The test system needs to ensure that the total resistance of personnel
wearing conductive foot-wear on a conducting flooring to earth should not exceed 106 ohms and that the total
resistance of a personnel wearing anti-static footwear or an anti-static floor should not exceed 10 x 106 ohms.
Where stores or compositions are segregated for investigation because of suspected micro joule sensitivity or
damage then these must be examined under conducting conditions, i.e. with maximum personnel to earth
resistance of 106 ohms. Personnel test meters are to be maintained in accordance with the operating instructions.
117. The method of siting of personnel test meter is important. Test meters should always be placed at the
entrance of the building i.e. verandah/lobby and the earth electrode should be connected to the earthed grid of
the conducting or anti-static floor of the building. The use of brass earth plates as foot electrodes is not
recommended as this does not check the actual conditions within the building.
SECTION-V
PERIODIC INSPECTION AND TESTING OF CATEGORIES OF
INSTALLATIONS
Inspection
118. Electrical installation are to be periodically examined for signs of mechanical failure such as corrosion of
conduit or conduit fittings and apparatus or damage to components due to overheating.
119. All terminals of flexible cables should be examined for tightness and signs of strand breakage. The metal
braiding or armouring should be examined for fraying or other damage.
120. Conducting and anti-static floors should be examined for excessive wear or mechanical damage.
121. Lightning protection installations should be inspected and all clamps, bonds and joints in the conductor
examined for tightness or signs of corrosion. Conductors should be examined for mechanical damage and
security of fixing.
Safety Equipment for Testing
122. No test is to be made on an installation in an explosives building without prior permission of the Head of
the establishment and unless the safety officer authorized to act on behalf of the head of the establishment, has
first checked that it is safe for testing. The safety officer is to remain in attendance throughout to ensure that
adequate safety precautions are taken.
123. Instruments which are certified as intrinsically safe should be used for testing installations within
explosives building.
124. Care is to be exercised when making line-earth or neutral earth loop tests to ensure that no hazard can arise
if the earthing circuit under test is defective.
125. Opportunity should be taken when a building is free from explosives to carry out testing.
126. If for any reason it is considered necessary to test with explosives stores in the building, special permission
is to be obtained from the Service HQ. The safety officer is to remain in attendance and ensure that the
following safety precautions are taken:
a) The distance between explosives (stacked or otherwise) and electrical conductors and equipment is kept to a
maximum during the testing and on no account should this distance be less than 0.5 m. This is particularly
relevant where wiring runs overhead.
b) Testing points for connecting instruments are to be well removed from ammunition or explosives and should
preferably be outside a room or building. No unsealed or exposed explosives is permitted within the area under
test.
c) The installation is to be under observation during testing and fire fighting equipment is to be immediately
available.
d) All the process activities in the room should be discontinued while testing is in progress.
e) On completion of testing shorting resistors should be used to discharge any residual capacitance charge and a
period of 30 seconds is to be allowed before disconnecting test equipment.
f) Immediately following testing all test equipment is to be remove from the explosives building.
Testing
127. The resistance of the earth continuity conductor should be tested before other tests are conducted.
Resistance measured between the main switch and any part of the earth continuity conductor should not exceed
0.5 ohm.
128. The insulation resistance of electrical installations between conductors and between conductors and earth
when tested should not be less than 1 mega ohms.
129. The resistance between the surface of a conducting floor and earth is to be tested with 500 volts insulation
tester using a wetted electrode. The maximum resistance between any part of the floor surface and earth should
not exceed 50 x 103 ohms.
130. The resistance between the surface of an anti-static floor an earth is to be tested in the same way as a
conducting floor. The resistance between any part of the floor surface and earth should not be greater than 2
mega ohms or less than 50 x 103 ohms.
131. The testing of lightning protection installation requires that on initial testing and after any modification:
a) The resistance to earth of each earth termination should not exceed the product given by 10 ohms times the
number of earth termination provided.
b) The resistance to earth of the installation with all electrodes and bonding of other service connected is not to
exceed 10 ohms when measured at accessible random points approximately equidistance from all earth
electrodes.
132. Communication fire alarms and intruder alarm systems are to be tested periodically to ensure satisfactory
and safe operation.
135. Flexible cables used with electrical appliances in buildings containing explosives are to be inspected and
tested at least once a month.
136. Conducting and anti-static floors are to be tested on installation and subsequently at intervals of 3 and 9
months. Thereafter the tests should be made at intervals not exceeding 12 months. The authority competent to
inspect and certify the conducting floor is MES in case of Services, R&D and DGI Organisation and in the case
of DGOF, it is the responsibility of the local maintenance engineer of the concerned factory.
137. In buildings where there is a high static hazard these tests should be made at more frequent intervals.
138. Protected electrical installations like flame-proof / dust-tight lighting fitting and motors may require
change of gaskets, washers, glands and other joints after these have been installed in explosives dust laden and
flammable corrosive vapours locations, after some time. When opened for maintenance purposes, the
accessories like gaskets, washers, glands, etc. should invariably be replaced by exactly matching types. For this
purpose it is desirable to keep a stock of such items. This aspect may be kept in view while procuring these
fitments.
139. Inspection and testing record should be maintained in a register and shown to Audit Officer at the time of
inspection.
„APPENDIX-B’
STEC SPECIFICATION FOR TOTALLY-ENCLOSED LIGHTING FITTINGS
0.1 In Explosives storage buildings and Process Buildings with no flammable vapour/gas or
flammable/explosives dust risk the use of totally enclosed lighting fittings which are mechanically sound and
weather and insect proof would be adequate. For this Purpose:-
(i) The body of the fittings should be sufficiently strong to withstand any damage likely to be met within the
course of normal usage.
(ii) It should be a completely closed fitting to prevent entry of extraneous material but need not necessarily be
airtight.
0.2 This standard is intended to cover the use of totally-enclosed fittings for incandescent and mercury vapour
lamps and tubular fluorescent fittings.
1. Scope: This standard covers lighting fittings of totally-enclosed construction intended for use in Explosives Building
without flammable gas/vapour and flammable/explosives dust risks.
2. Terminology
2.0 For the purpose of the standard, the following definitions shall apply:
2.1 Totally-enclosed – A fitting protected by mechanically sound enclosure weather-proof and insect-proof,
without opening for ventilation but not necessarily air-tight.
2.2 Lighting Fitting – Apparatus which distributes, filters or transforms the light given by one or more lamps,
and which includes all the items necessary for supporting, fixing, connecting and protecting these lamps
and, if necessary, the auxiliaries for their operation. A simple lamp holder however, does not constitute a
lighting fitting.
2.3 Rated Voltage – The nominal mains voltage for which the lighting fitting is designed.
2.4 Rated Wattage – The total rated wattage of the lamp for which the lighting fitting is designed.
2.5 Routine Test – Test carried by the manufacturer on each fitting to check requirements which are likely to
vary during production.
2.6 Type Test – Tests carried out at the Testing Section to prove conformity with the specification. These are
intended to prove the general qualities and design of a given type of lighting fittings.
2.7 Weather-Proof – Applied to apparatus to denote that the live parts are enclosed by a cover or covers so
constructed as to exclude rain, snow and external splashing.
3. General Requirements: 3.1 Totally enclosed lighting fittings shall comply with the requirements of this assembled including the
attachment of cable or conduit, the assembly shall be mechanically sound and the fitting weather-proof and
insect-proof. They shall be constructed from such materials and have such finishes that no undue deterioration
occurs during normal life.
4. Material and Construction:
4.1 The body of the fitting shall be cast iron, aluminium alloy or other suitable metal. The metallic retaining
ring for the glass shall be of cast iron or mild steel or any other suitable material of adequate thickness. They
shall be free from cracks, blow-holes and other flaws. The strength and rigidity of the enclosure shall be such
that there will be no subsequent twisting or warping due to any nominal inequality of the surface on which it is
mounted.
4.1.1 The gaskets shall be of homogeneous material throughout and shall be without a joint, thoroughly
compressed, reasonably free from air holes and all other imperfections. The gasketed ring shall be made of any
suitable material which shall not deteriorate in normal use.
4.1.2 Control Gear – Where control gear for discharge lamps is accommodated within the street lighting
luminaries enclosure, the design, construction and workmanship shall conform to IS; 1913-1961 General Safety
Requirements for Electric Light Fittings.
4.2 Joints-The surface of the joints and glass shall be flat and free from any unevenness and inequalities.
4.3 Lamps-Fitting made to the Specification shall accommodate TUNGSTEN filament lamps of the appropriate
voltage complying with IS 418-1978 specification for Tungsten filament general service electric lamps, mercury
vapour discharge lamps in accordance with IS: 9900-1981(Part 1) to (Part 4) High Pressure mercury vapour
lamps or tubular fluorescent lamps.
4.4 Lamp Holders – The lamp holders shall be of metal / alloy or porcelain and they shall comply with the
relevant Indian Standard (see IS: 1258 – 1987, specifications for Bayonet lamp holders).
4.5 Glass and Plastic Enclosures:
4.5.1 Where glass or plastic enclosures are used, these part should be firmly held yet easily replaceable. They
should be well sealed by the use of suitable gaskets but readily accessible for cleaning and maintenance. They
should be resiliently mounted free from stress and so secured that in the case of plastic warping is minimized.
4.5.2 Plastic enclosures shall be made sufficiently large to obviate over-heating when used with the largest lamp
recommended by the manufacturer under the worst possible weather conditions.
4.5.3 Glass or plastic enclosures shall be capable of withstanding thermal shock due to rain and stresses due to
other causes in normal operation when the street lighting luminaire is equipped with each of the light sources
for which it is designed.
4.6 Provision for Reflectors – Provision may be made on well-glass fittings for the attachment of reflectors if
required. If provided the material and finish of reflectors shall comply with the relevant Indian Standards
Specification (see also IS: 1777-1978-specifications for Industrial luminaire with Metal reflectors).
4.7 Provision for guard-The lighting fittings shall be provided with guard. Bars in such guards shall be of metal
and, when in round sections, shall have the following minimum dimensions:-
Diameter of Basket Diameter of Bar
(mm) Above
(mm)
Upto and including
(mm)
75 3
75 100 4
100 5
In the case of bars other than round in section they shall have a minimum cross-sectional area of 20 mm2.
At points where bars cross, they shall be firmly fixed, for example, by welding.
The dimensions of openings in such guards shall be as follows:
Max.
Upto 60 W 40 mm x 50 mm
Above 60 W and upto 200 W 50 mm x 70 mm
Above 200 W 60 mm x 100 m
Variation from the maximum on the lower side shall not exceed 10%.
The minimum distance of the protective bars from the glass shall be:-
External diameter of the body in the case of well-glasses and maximum dimensions in case of bulkhead
glasses:
Upto 100 mm 7 mm
Above 100 mm 10 mm
Note: In lighting fittings with glass windows, it shall be not less than 5 mm.
The wire guards shall be so fixed to the main part of the lighting fittings that the use of special tools shall
be essential to remove them.
4.8 Finish – The fittings shall have a neat finish and the metal parts shall be either stove enamel painted or
otherwise treated to render them dust-proof.
5. Provision for earthing
An earthing terminal shall be provided to enable the fitting to be earthed. The earthing terminal shall have
screw thread corresponding to M6 (See IS: 1362-1962) Specification for Dimensions for Screw threads for
General Purposes Diameter range 0.25 to 39 mm (Revised).
6. Warning Inscription
The totally-enclosed fitting shall carry an inscription warning against opening the enclosure unless circuit
is isolated elsewhere or the fitting shall be so designed that access to the lamp inside cannot be obtained
unless the circuit is rendered dead.
7. Temperature rise
7.1 The temperature rise at any part of the external surface of the fitting shall not exceed 500 C in the case
of incandescent and 400C for tubular fluorescent and mercury vapour lamps when measured in an ambient
temperature of 500 C. In other words the maximum temperature on the surface at such ambient temperature
shall not exceed 1000C for incandescent and 900 for tubular fluorescent and mercury vapour lamps.
7.2.1 If the fittings are designed to include an external reflector, the temperature rise shall comply with this
requirement either with or without the reflector.
8. Marking
8.1 Each fitting shall be permanently marked either by raised lettering or cast integrally with, or by a plate
attached by reverting to the body of the fitting in a manner which will not impair the totally enclosed
enclosure, to indicate the following particulars:
(a) Manufacturer‟s name and / or Trade Mark.
(b) Country of Manufacture.
(c) Model and type designation (i.e. T.E.)
(d) Rated wattage
(e) Max. Rated voltage.
(f) Temperature range latter i.e. Max. Temp rise 500 C/400 C in Max. Amb. 500 C.
8.2 Marking of Earth Connection – The earthing terminal shall be identified by the symbol „I‟ marked in
legible and indelible manner or adjacent to the terminal.
9. Tests:
9.1 Routine Test-The following shall constitute routine tests:-
(a) Insulation Resistance (Dry) – The test-resistance should be measured by the application of 500 V DC
for one minute between:-
(i) Live parts of different polarity inside the fitting and
(ii) Live parts and external metal parts of the fitting. The insulation resistance shall not be less than 5 mega
ohms.
(b) High Voltage Test – 1000 V RMS is applied between the parts mentioned at (a) (i) and (ii) above and
the fitting examined to see whether it can withstand the above voltage without any puncture or arcing.
9.1.1 Certificates of the above route tests shall be forwarded by the manufacturer to the Testing Authority
along with the sample under test.
9.1.2 Type Test:
a) Weather Proofness – Artificial rain is applied at an angle of 450 to the fitting for an hour. Entry of water
within the interior of the lighting fitting shall be taken as non compliance with the definition of weather
proofness.
b) Test for temperature rise-The test shall be carried out in a rectangular draught proof enclosure with the
lamp when giving the greatest rise in temperature. Thermo couples are used to record the temperature by
measurement of the EMF developed. The thermocouple may be attached to the surface so as to get a good
thermal contact with the minimum of disturbance of the thermal conditions. Attachment may be by
mechanical means, soldering, adhesive or by thermocouple holders suitable for the well-glass or bulk-head
fittings.
c) Thermal shockproof test for cover glass – The purpose of the test is to examine whether the cover glass
could stand sudden variations in surface temperature for example by falling rain or splashing water when it
is operating, without developing cracks. The test consists of heating the cover glass in an oven to attain a
steady temperature of 1000 C (maximum permissible surface temperature)and plunging it in cold water and
examining for any cracks or defects.
9.1.3 Details of the weather proofness test are attached as annexure to this Standard and for other two tests
refer, IS: 4013-1967.
ANNEXURE TO APPENDIX ‘B’
Weather Proofness Test:
(i) An artificial rain shall be applied at an angle of approximately 450 to the vertical to the fitting as
mounted in service. The rain shall be applied for one hour at an approximate rate of 3mm per minute. The
rate of rainfall shall be measured by the rise of water in a small straight sides pan placed horizontally and
completely within the area covered by the rain.
(ii) The water shall not come into contact with the enclosed electrical equipment and the interior of the
fitting.
(iii) Immediately afterwards the insulation resistance of the fitting shall be measured in accordance with
9.1a and the measured value shall be not less than 2 megohms.
‘APPENDIX-D’
INSTRUCTIONS FOR INSTALLATIONS OF LIGHTNING PROTECTION
SYSTEMS
POLICY FOR THE PROVISION OF LIGHTNING PROTECTION TO DEFENCE EXPLOSIVES
INSTALLATIONS as given by letter No.95325 STEC, R&D 20/III/217/D (R&D), Govt. of India,
Ministry of Defence, New Delhi dated 6th January 1971.
1. Subject to the provision that lightning protection may be waived in Forward areas if the explosives
storages as in wooded jungles, deep valleys or protected by adjoining cliffs of hills, lightning protection
shall be provided for:-
(a) All magazines and explosives store houses in K.L.P. areas including explosives buildings in Ordnance
Factories and Allied Establishments having a net explosives content of 250 kg or over 5 tonnes gross
whichever is less, all explosives process buildings and ammunition workshops and buildings storing 5000
litres or more of petrol or other highly flammable liquids held in explosives installations.
(b) All buildings in Non K.L.P. areas including fields and Forward Area having a net explosives content or
500 kg or over or 10 tonnes gross whichever is less or 10,000 litres of petrol or more or other highly
flammable liquids held in explosives installations.
(c) All open stacks/dumps of ammunition explosives (including those under tarpaulin or tent) having a net
explosives content of 500 kg or over or 10 tonnes gross whichever is less or 10,000 litres or more of petrol
or other highly flammable liquids when stored other than in tanks duly earthed, which are intended to be
retained for more than 1 year in an explosives installations. Therefore, it will be necessary that action be
taken to sanction the provision of lightning protection system as early as possible and well within a period
of one year.
Note: In exceptional cases, however lightning protection system may have to be provided even when the
quantities involved are less than those specified above.
2. Lightning protection required for buildings structures, installations should be in accordance with IS Code
of Practice IS: 2309 as amended from time to time and as approved by the Engineer-in-Chief, Army Head
quarters, New Delhi with particular reference to sub-para (a) and the exceptions detailed at Sub-para (b)
below:-
(a) (i) Aluminuim may be used in lieu of copper in lightning protection system above ground.
(ii) Galvanised iron may be used in lieu of copper below ground or above ground.
(iii) The resistance to earth must not exceed the following
At the time of installations - 7 ohms
During periodical tests - 10 ohms
(iv) Pole type system of lightning protection should be installed for open storages including ones under
tents/tarpaulins in K.L.P. areas and wherever possible for temporary buildings/structures/installations in
Non-KLP areas and for storage in the open.
(b) In non-KLP areas with thunder days less than 30 in the year and where lightning strikes involving
serious loss of property has not been recorded in the past ten years, the zone of protections should be taken
as a cone of height equal to the mast height and base of radius equal to the height of the conductor.
3. Cases for providing lightning protection for Defence Explosives Installations not covered by this letter
including proof yards and other non explosives buildings within the explosives area should be examined by
the Service/Branch etc. with reference to various relevant factors i.e. nature of the structure and its use,
value of stores, equipment and machinery, lightning risk in the region and the risk to adjacent utilities etc.
4. Existing lightning installations provided in accordance with Regulations current at the time of their
erection need not, however be altered provided there are in a satisfactory condition and serve the purpose
for which they are intended. They should be retained and properly maintained until the necessity for
extensive repairs or replacement provides in opportunity for adopting the standard type to installations in
accordance with the provisions of this letter.
5. In cases where it is not possible to comply with these Regulations necessary deviation may be accorded
by the appropriate Service authorities as are authorized.
6. Annexure to this letter lists the types of lightning protection systems to be provided to the various
categories of explosives buildings with different types of risks and also for non-explosives buildings in
explosives area in Ordnance Factories and Explosives Depots to serve as a guide line for installations of
Lightning Protection system.
7. Each project will be sanctioned by the competent Financial Authority and carried out according to
normal works procedure.
‘APPENDIX-E’
LIST OF EXPLOSIVES AND EXPLOSIVES STORES REQUIRING ANTI-STATIC
PRECAUTIONS
The following list of explosives requires anti-static precautions to be taken when exposed and handled:-
(1) All initiatory compositions with a spark sensitivity of less than 0.001J.
(2) All EEDs which may be initiated below an energy level of 0.001 J.
(3) Pyrotechnic compositions:-
(a) Delay composition (gasless) based on Boron as fuel and Lead and Barium peroxides, Chromium,
Bismuth and Molybdenum trioxides as oxidant: SR 54, SR 56, SR 57, SR 61, SR 75, SR 79, SR 87, SR 89,
SR 90 and SR 92.
(b) Igniter and primary compositions based either on Zirconium as fuel with Molybdenum or Chromium
trioxide as oxidant or Aluminium and/or Magnesium as fuel with Cupric oxide and Tungsten trioxide as
oxidant: SR 45, SR 46, SR 47, SR 70 and SR 72.
(c) Flame compositions based on Titanuim as fuel: SR 697, SR 698 and SR 699.
REGULATIONS ON AIR-CONDITIONING AND HUMIDITY CONTROL
IN EXPLOSIVES AEAS
Introduction
1. In recent years there has been a phenomenal rise in the requirements of controlled atmospheres for
manufacturing processes and for prolonging shelf life of costly and sophisticated explosives/ammunition
stores. These requirements now-a-days vary widely with temperatures dipping to 20 0C (68 0F) and
relative humidity ranging from a minimal 20% to values as high as 80%. With the tropical and coastal
climates prevalent in India, the need is frequently felt for cooling by air-conditioning during hot and humid
seasons. Quite often, humidification and dehumidification, heating in winter and even evaporative cooling
are also required individually or in conjunction with air-conditioning. A combination of summer cooling
and winter heating will provide round-the year-conditioning.
2. Air-conditioning, strictly speaking, constitutes simultaneous control of temperature, humidity, purity and
distribution/motion of air in a confined conditioned space. For modern production and storage practices,
control of most or all of the above mentioned factors is absolutely vital and so air-conditioning has become
an important backbone of industries.
Fundamental Principles
3. Air-conditioning comprises of basic refrigeration system and air-handling equipment for circulation of
treated air. The refrigeration portion works on the popular vapour compression system consisting of a
refrigerant compressor driven by an electric motor, a refrigerant condenser of the air-cooled or the water-
cooled type, a receiver to store liquid refrigerant (which is sometimes incorporated in the condenser itself),
an expansion valve, finned cooling (evaporator) coil and interconnecting refrigerant piping (Fig. 1). Clause
2 “Terminology” in IS 660-1963 “Safety Code for Mechanical Refrigeration” (revised) g0ives the brief
purpose of these components. The air-handling equipment houses the cooling coil of the refrigerating
system, air filter, air blower driven by an electric motor and the humidification apparatus (if provided). The
supply and return air ducts convey the conditioned air to and from the conditioned space. The refrigerant
circuit its entirely independent of the treated air circuits.
4. In the simplest form, this system can maintain temperature as low as 18 0C (64 0F) and relative humidity
around 40% For obtaining lower conditions than these, special features will have to be incorporated in the
air-conditioning system and sometimes in the conditioned building also. Winter heating arrangements
(where required) can easily be incorporated into this system.
5. In the arrangements shown in Fig. 1, air from the conditioned space is taken back through the return air
duct to the air-handling unit and recycled along with some fresh air drawn in through the air filter. Thus
there is recirculation of air from the conditioned 5 space and for all practical purposes, the weather-maker
room could be considered to be a part and parcel of the air-conditioned space itself. Allowing for leakages
of air from the conditioned space to outside, it is possible to recirculate as much as 95% of the air in the
conditioned space. Increased recirculation results in a smaller plant and all round economy.
Inherent Dangers
6. In process and laboratory building where explosives are manufactured and processed, explosive
vapours/dust are invariably generated. Thus in the arrangement shown in Fig. 1, the explosive vapours or
dust generated in the conditioned space will reach the weather-maker room through the return air duct. The
equipment installed in it. It will also flow through the air-handling unit coming into contact with the air-
filter, cooling coil, blower and motor etc. before being blown through the supply air duct into the
conditioned space.
7. The inherent danger of fire and/or explosion occurring in any part of the air duct and the weather-maker
room, therefore, exists. The explosive dust may settle in the air ducts to form an encrustation, which is
difficult and dangerous to deal with. Similar settlement occurs in the weather-maker room and the duct
accumulates rapidly in the air filter. The presence of explosive dust in this fashion poses serious danger
during inspection and maintenance / repair operation, as an explosion can easily result from surface friction
produced by rubbing or a spark struck during the operation. Any fire or explosion in the conditioned space
will spread into the weather-maker room through the ducts and vice versa.
8. The design and specifications of the air ducts and the adjuncts, accessories and equipment installed in the
weather-maker room, therefore, assume paramount importance. It is equally desirable to pay full attention
and care to the design and construction of the weather-maker room and the conditioned space/building. All
decisions and provisions should be totally safety oriented. Ad-hoc or temporary arrangements for air
conditioning even for a short duration are NOT acceptable.
Fresh Air Changes and Recirculated Air
9. Inspite of recirculation of air form the conditioned space, a certain quantity of fresh air from an
uncontaminated ambient source has to be inducted into the system to provide for metabolic needs of the
occupants, to maintain freshness and to make up for the inevitable loss of conditioned air by leakages
through cracks/door openings. The fresh air so admitted replaces continuously the air in circulation and
provides a certain number of fresh air changes in the conditioned space every hour which equals:
Volume of fresh air inducted per hour
Volume of conditioned space
The values of fresh air required for occupants are given in IS: 659-1964 “Safety Code for Air-conditioning
“(Revised)”. These norms stipulate an insignificant fresh air 6 change rate when the occupants are few or
the conditioned space volume is large. Practical considerations dictate the minimum fresh air changes per
hour to be one. An increase in fresh air changes per hour reduces the proportion of recirculated air and
diminishes the pollution prospects inside the conditioned space which is a positive step towards safety.
10. To illustrate the point, repetitive calculations with increasing number of fresh air changes per hour have
been made assuming certain data and the results are tabulated below:
Data assumed: Conditioned space 12m L x 6m B x 3.5m H
Brick walls, PCC floor, and RCC roof with 25mm insulation.
Inside temperature 76 deg F, RH 50%
Occupancy 8 persons.
Internal electric equipment load 2 KW. 7
plant capacity (col. 6) for this particular case. It shows that one fresh air change (serial I) would entail
recirculation or nearly 95% of the air from the conditioned space, and equal proportion of fresh air and re-
circulated air occurs at 11 fresh air changes (Srl 8). With 28 fresh air changes (Srl 8) there is no need to
resort to recirculation and the system can work on all (or 100%) fresh air itself. The plant capacity leaps
from a mere 5.7 tons with one air (Srl 1) to 24.5 tons with 100% fresh air (serial 18), and thereby highlights
the importance of judicious appraisal of fresh air requirements (see para 16).
12. It is obvious that change in any value of the data assumed in the above case will influence the
calculated values. A simple change in the value of electric power consumed by user equipment alone
(assumed as 2KW in the above case) will provide a striking example of the effects on air quantity and plant
capacity as shown below:
Sl. No. Electric power
consumed by
equipment in
conditioned space
KW
All fresh air (no
recirculation)
occurs with
following fresh air
changes per hour
Plant capacity tons Remarks
1 2 3 4 5
1.
2.
3.
4.
5.
6.
2
4
8
12
15
20
28
30
38
45
50
58
24.5
26.6
33.0
38.5
45.0
58.5
Repeated form
previous table.
13. It therefore becomes apparent that the above-calculated figures can project only a very generalised picture
on which a universal yardstick cannot be formulated. The importance of detailed calculation for every
individual situation based on actual ground data can also be realized.
14. The number of fresh air changes per hour to be adopted is governed by several factors, such as the quantum
and nature of the pollutant (e.g. vapour or dust, coarse or fine, light or heavy, safe/unsafe, harmful to
men/materials etc.) introduced by the process/activity in the conditioned space. Generation of loathsome or
nauseating small or vapours by the process in the conditioned space could also be an important contributing
factor. So longer the working hours, the greater are the chances of progressive accumulation of pollutants. Due
to the compensating / cumulative effects of the various factors involved, no hard and fast scale or guidelines for
every possible situation can be laid down in case of explosives buildings. The broad guidelines are:
(a) The fresh air change rate selected should ensure that the atmosphere in the conditioned space is maintained
at a pollution level well below the risk level at all times. The level of pollution concentration in the conditioned
space should not be a health hazard to the occupants.
(b) In the range of ONE to FIVE fresh air changes per hour, the air under recirculation is considerable
(above 75%). Utility of this range for any explosives process/laboratory building is doubtful. This could
possibly be considered for buildings used for storage of explosives.
(c) Where intake of generous quantity of fresh air becomes essential and the quantum of re-circulated air is
to be restricted (to about 10% or less), it may be more advantageous to adopt all fresh air arrangement (see
para 15).
15. Where recirculation of air from the conditioned space is dangerous and is not desired, the return air
duct is omitted and entire quantity for air required for air-conditioning is drawn in from outside fresh air.
The air in the conditioned space is exhausted to atmosphere by deliberate leakage or sometimes forcibly by
means of exhaust fans. This results in all fresh air system (and no recirculation) and directly involves a
tremendous increase in plant capacity and recurring expenditure. Even in this system, explosive
vapours/dust generated in the conditioned space can enter the supply air duct when the plant is shut down
or is not in operation and pass along to the weather-maker room. Thus the possibility of danger cannot be
ruled out and full attention to all safety aspects has to be paid.
16. As mentioned in para 11, a careful approach to the selection of fresh air changes is essential because of
its impact on plant capacity/recurring cost. At the same time the following factors should also be borne in
mind:
(a) Inducting massive fresh air quantities involves an equivalent discharge or polluted air from the
conditioned space to the free atmosphere. Any danger posed by the quantum of explosives contained in the
discharged air should be carefully appreciated and suitable action taken to ensure safety.
(b) Fresh air change rates of TEN and OVER creates significant positive air pressure inside the conditioned
space. The effect of this conditioned but polluted air under pressure on the electrical fitments and other
gadgets (which may be of pressurized type) is to be carefully appreciated and suitable steps taken to ensure
safety.
17. For category „A‟ buildings involving flammable/explosive vapours, recirculation of air is NOT
recommended from ultimate safety angle and all fresh air system shall only be adopted. In case of Category
„B‟ buildings involving explosive dust and Category „C‟ buildings, recirculation of air is permitted to the
extent that it does not create unsafe levels of explosive dust concentration. Sufficient quantity of fresh air
shall be admitted at all times to ensure that the explosive dust concentration everywhere is well below the
acceptable risk level. Keeping in view these aspects, it is recommended that for category A, B and C
explosive buildings, 100%, 50% and 25% fresh air changes per hour should be followed respectively.
Where air recirculation is accepted, the return air duct should not end at the entrance point to the weather-
maker room but should extend right upto the air-handling unit and be rigidly connected to it.
18. In some cases, air-conditioning is required for cooling during summer/monsoon seasons and it is
possible that the plant will be shut down during the winter months. If the Air-handling unit is also switched
off, induction of fresh air and circulation of air through the conditioned space will cease, which cold result
in a build up of pollutant inside the conditioned space. This is dangerous. If the air-handling unit is kept
working, then it will create circulation of cold air. This could prove uncomfortable to the occupants who
may rightly insist on the stoppage of cold air draughts. Therefore, to maintain air circulation during winter
and still ensure comfort, it will be necessary to incorporate winter heating with the air-conditioning system
of the building used for process/laboratory work. IS: 659-1964 “Safety Code for Air-conditioning
(Revised)” gives inside design conditions for human comfort during winter months. Operation of the air-
handling unit and normal movement of air should never be interrupted during the working hours. Spare
blower, motor and controls, etc. should be held in ready stock for emergent use to minimize down time.
Types of Air Conditioning Plants
19. For ready off-the-shelf availability, the air-conditioning manufacturers have brought out the room air-
conditioner (also popularly called as window air-conditioner) and the package type air-conditioner. In
addition, the central type of air-conditioning plant is also in vogue. These are briefly described in the
succeeding paragraphs.
Room (or Window) Air-conditioner
20. These air-conditioners are factory assembled composite small units, mass produced for instant use for
providing human comfort conditions (Fig. 2). The most popular sizes are the 1 Ton and 1.5 Ton units.
Room air-conditioners are covered by IS: 1391 – 1971 (First Revision). The only advantage attributable to
this type are the ready availability coupled with instant installation as plant room, ducting, elaborate
electric water services are not required.
21. These air-conditioners have several limitations as given below:
(a) They can lower the room temperature by a maximum of 14 to 17 0C (57 to 63 0F) from the ambient, but
they cannot control the inside temperature effectively.
(b) They are totally ineffective in controlling relative humidity.
(c) They have to work with maximum recirculation of air and cannot provide more than about 1½ fresh air
changes per hour.
(d) They have to be mounted on the periphery of the space to be conditioned. The blower unit is small and
hence does not permit provision of air ducts.
(e) Their capacity of filter air is very nominal. They do not give sufficient air circulation in the room also.
(f) The electrical components incorporated are normal and cannot be improved due to space restrictions.
22. In view of the above limitations, these machines are NOT suitable for use in explosive buildings.
Split type air conditioners
22A. These are factory assembled units in standard capacity of 1 ton, 1.5 ton, 2 ton and 2.5 ton. In split
type air conditioners the compressor & motor as well as condenser and its cooling fan are located at a
distance from the air conditioned space. In explosive buildings where no humidity control in required, the
split air- conditioner to be used should meet the following stipulations:
(i) The blower motor should comply with the standards specified for the electrical installation in the bldg.
in which it is being used.
(ii) All the control switches for the blower unit should be located in the compressor room for split air-
conditioner and compressor room should be located beyond the traverse wall of the building.
(iii) The compressor motors and all the electrical installation/ apparatus associated with it in the compressor
room should be totally enclosed (TE) type.
(iv) The split air conditioner should be got certified from CMRI, Dhanbad for use in explosive buildings.
Package Type Air-conditioner
23. These are also factory assembled units in standard capacities of 5 ton, 7.5 ton and sometimes 10 ton.
Their shape resembles steel almirahs, the compressor-motor-condenser unit being located in the lowest
portion and the middle and top portions containing the air filter-cooling coil and blower-motor unit (Fig. 3).
They are invariably water-cooled and need pump sets with cooling towers. A plant room has to be provided
to house them and their accessories. Since the blower unit is somewhat powerful, short lengths of supply
and return air ducting can be provided for air distribution in the conditioned space and for installing the
units in a separate adjoining room. Also the manufactures sometimes agree to modify their standard design
slightly to suit customer‟s requirements of temperature, relative humidity, air purity and quantity. These
units, being somewhat bigger require adequate external electric/water supply services.
24. Their construction is such that the air handling unit cannot be effectively sealed and separated from the
compressor-motor compartment. Hence flammable/explosive vapour or dust reaching the blower through
the return air duct has easy access to the compressor-motor unit. This can prove to be very dangerous. So
also the explosive vapour / dust can leak out of the unit and spread inside the plant room coming in contact
with all electric gadgets provided therein. This enhances the risk of fire and explosion.
25. Since it is possible to adopt central air-conditioning system of equivalent capacities and incorporating
the requisite safety specifications, the use of package type air-conditioners in process buildings is not
desirable. However in explosive storage bldgs, the package type air conditioners are permitted with
following stipulations:
a) The blower motor and compressor motor and all the electrical installations in the weather maker / plant
room should be totally enclosed type.
b) The plant room including weather maker room should be sited beyond traverse wall and only ducting
should be used to connect the air conditioned space and weather maker room.
c) Approved type of fire dampers as per specification given in STEC pamphlet No. 22 should be installed
in A/C duct so as to ensure that in case of fire emanating from weather maker room plant room, it does not
travel to conditioned space & vice versa.
Central Air Conditioning Plant
27. A typical central air-conditioning system is depicted in Fig. 4. In this case the individual components of
the system are specially selected, matched and put together at site to provide the specified inside conditions
of temperature, relative humidity, air purity and quantity, air flow pattern, etc. The system is similar to that
shown in Fig. 1 and should NOT be confused with a “centrally located” plant.
28. These installations are tailor made for a specified and predetermined purpose and could be of any
capacity to suit the requirements. They need plant room, air ducting, pump sets and cooling tower,
adequate and reliable external electric/water supply services and trained operators. The most important
factor in their favour is that adequate and requisite safety can easily be incorporated to make the
installations safe for use in explosive buildings.
29. As central type air-conditioning plants can be rendered intrinsically safe and can provide guaranteed
performance to comply with specified conditions, their choice is automatic in almost all cases.
30. Central air-conditioning plants could work either on the direct expansion system or the chilled water
system which are described below:
(a) Direct expansion system: In the system depicted in Fig. 1 and F. 4, the air under circulation is cooled
directly by the refrigerating plant‟s cooling (or evaporator) coil. This arrangement is simple and direct in
nature. The air-handling unit has perforce to be as near as possible to the rest of the refrigerating machinery
and the length of supply/return air ducting is limited by practical consideration which places a certain
restriction on the size of space that could be conveniently air-conditioned with one air-handling unit.
(b) Chilled water or indirect system: This is shown in Fig. 5. Ordinary clean water is chilled by the cooling
(or evaporator) coil of the refrigerating plant and then pumped through the cooling coil of the air-handling
unit where it cools and conditions the air passing over it. This system enables one air-conditioning plant of
adequate total capacity to condition very large areas with multiple air-handling units or several
buildings/several floors of the same building with separate and individual air-handling units. Also the air-
conditioning plant room itself could be located at the center of gravity of the load or at a convenient
distance away from explosive buildings. The chilled water pipes are insulated and covered with suitable
protective material, and can be run either below or above ground in any fashion that is convenient.
Air-handling Units
31. The air-handling unit conditions the air and the blower provided in it creates the air flow through the
supply and return air ducts. The air-handling units (which generally contains air filter, cooling coil,
humidifier, blower and motor etc.) is exposed to the effects of the explosive vapour/dust particles that are
carried to it via the air ducts. In fact, by and by, the complete weather-maker room itself gets polluted by
the explosive material and the olfactory senses can easily detect the presence of the same atmosphere here
as in the main building. The provisions for the weather-maker room should therefore compare with those
for the conditioned buildings.
32. Air filters are provided to obtain the desired purity of the circulating air by filtering solid particles.
They are not effective against vapours. Air filters provided on the fresh air intake get rid of the atmospheric
dust and floating matter. Air filters can also be incorporated in the air-handling unit and or in the return air
duct to trap dust particles emanating from the conditioned space. However, while the air filters function
effectively in trapping the explosive dust, it should be realised that the explosive dust particles keep on
collecting at the filter material and may soon reach a high concentration level. The air filter then becomes a
very dangerous spot where an explosion or fire can easily occur due to the rubbing effect/friction generated
while removing the filter panel for maintenance. Hence indiscriminate use of air filter in the return air duct
should be avoided. The design of the air filter unit should be such that no rubbing or sliding effect or
friction is involved in the assembly or disassembly operations done during periodical maintenance. Air
filter material should inherently be non-combustible. Coir and paper based filter materials should not be
used. A wetted type or viscous type of filter is preferable from safety angle. No definite periodicity can be
laid down for inspection or maintenance of air filters, but the same should be governed by actual ground
conditions.
33. Cooling coils are made of copper or aluminium tubing with fins of copper or aluminium. It is essential
that the explosive vapour or dust has no deleterious effect on the cooling coil material. Some examples are
given below :
Metal Compatible Incompatible
Aluminium
Copper
CE, RDX, Hexolite, TNT,
Nitrocellulose, propellants both
single and double based.
CE, TNT, NC propellant, lead
styphnate.
PETN, Pentolite, gun powder.
RDX, gun powder.
Air Ducts
34. Supply and return air ducts are provided for conveyance of air from and to the conditioned space.
Supply and return air grills are provided on the air ducts at appropriate places to control the volume of
airflow from and into the duct. IS: 655-1963 (Revised with amendment No. 1) deals with “Metal Air
Ducts”.
35. Air ducts are a great source of danger arising from accumulation of explosive vapours or dust particles
inside them. These are made with airtight joints and generally covered by insulating material and false
ceiling, which hampers subsequent strip inspection and maintenance. Fine explosives dust carried along by
the motion of air settles inside the ducts to form an encrustation so hard that it cannot be removed even by
chipping. Also if the return air duct is terminated at the entrance to the weather-maker room (as shown in
Fig. 1), then the explosive material will spread in the weather-maker room. This fanning out of explosive
material could be dangerous. Hence connecting the return air duct to the air-handling unit, as shown in
Figs.5 & 6, may be more advantageous. It is very important that design, fabrication and installation of ducts
are done with utmost care and foresight.
36. The air ducts, once fabricated and installed, are rather difficult to inspect and maintain. Since these are
a source of greatest danger, dedicated efforts should NOT be spared towards their regular inspection,
maintenance and safety checks. No hard and fast maintenance/inspection periodicity can be specified, but
these are to be determined by the actual ground conditions.
Fire Dampers
37. All ducts provide a convenient passage for fire to travel and spread out. Fire dampers are used to block
the flow of air and prevent, propagation of fire through air ducts. It is mandatory to install fire dampers for
all air-conditioned explosives buildings. These could be designed for manual or automatic operation.
Automatic fire dampers are generally held open by a fusible link which melts when heated to a
predetermined temperature and allows the damper to close shut. However, their operation could also be
controlled by electric solenoids triggered by fire alarm systems.
38. Fire dampers are generally required at the following places:
(a) Where the duct passes through a fire partition having a fire resistance rating of not less than two hours.
(b) Where supply or return branch ducts are connected.
(c) Where a branch duct goes through a fire resisting ceiling or floor.
(d) Where the duct passes vertically through an opening.
Air Washers
39. Washing of the return air from the conditioned space by water spray bank could be very effective in
extraction of explosive dust particles (see Fig. 7). The water spray bank and spray eliminators (for
preventing water droplets from being carried away by air) could be conveniently tucked into the return air
duct itself or could be arranged in a separate ante-room beside the weather-maker room. Depending on the
pollution level in the return air, water spray washing could be duplicated to ensure maximum settlement of
explosive particles thereby rendering the return air to the air-handling unit as safe as possible. Care should
be taken to employ sufficient number of spray nozzles with correct spacing and the water pressure should
be sufficient to result in a fine misty spray. A water filter should be provided to ensure that nozzles do not
get clogged with dirt. A toughened glass view window should be provided to enable visual check of the
water spray. The water pump and sump could be located in safe area far removed from the explosives
contaminated area. Effective make-up water and drain connections should be provided. The periodicity for
water change over should be fixed based on actual ground conditions and the disposal of sludge / dirty
water should be done following safety procedure. Air washers can be effectively used for cleansing the
return air, but they cannot reduce the pollution level inside the conditioned space itself.
40. Water spray washing increases the relative humidity of the return air and imposes additional cooling
load on the air-conditioning plant. But this is a small sacrifice to make compared to the important
advantages accruing form the use of this cleansing system. Water spray washing is suitable for use in place
of air filter sin the return ducts.
41. Water spray washing of return air should not be carried out with chilled water from the chiller unit. The
water loop of the water spray system should be distinctly separate from the chilled water loop and the
condenser cooling water loop of the air-conditioning plant.
Humidification and Dehumidification
42. Humidification involves addition of moisture to the air to increase its relative humidity. This is an
important operation and is resorted to for facilitating certain production processes and to reduce generation
of static-electricity which is otherwise produced in dry air-conditions. This is mostly used in conjunction
with air-conditioning and sometimes by itself.
43. Humidification could be achieved in the following ways:
(a) Steam pan humidifier: Water in a flat pan is heated by electric immersion heaters and evaporated to add
moisture to the air. This system is susceptible to danger as the electric heater can develop high temperature
in the absence of water.
(b) Steam jet humidifier: Low pressure steam is admitted in a controlled fashion directly into the air stream
or into the conditioned space itself to add moisture to the air. This system can give high relative humidity,
but has a tendency to increase the inside temperature due to the steam latent heat, or add to the cooling load
on the air-conditioning plant. This method is therefore NOT always convenient.
(c) Dry team diffusion type humidifier: Steam at low pressure is first dried and then throttled through a
screen before it is allowed to mix with air stream. Apparently this has the same disadvantage as the steam
jet humidifier.
(d) Water spray humidifier : A fine, misty spray of water could be added to the air stream and three ways of
achieving the same are as under :
(i) By a pump and spray nozzle combination located near the cooling coil. The air stream passing through
the spray picks up moisture and relative humidity of upto about 60% can be achieved. This method has the
added important advantage of cleansing the air of explosive dust particles.
(ii) By compressed air and spray nozzle combination located in the air stream or directly in the conditioned
space. Compressed air forces the water through minute orifices and the water issues forth in the form of a
mist. This method is simple and safe, but needs an air compressor and does not assist in removing
explosive dust particles.
(iii) By spinning plate atomizer principle: Water is forced by an electric motor driven pump through
orifices in a spinning plate. This generates a fine mist of water. Since the motor is of normal specifications,
this method is unsafe for use in explosive buildings.
(e) Evaporative cooling of air: Air is drawn through a water spray bank created by pump nozzles
arrangement. The air evaporates the minute water particles and thereby picks up moisture. It also sheds the
explosive dust particles and becomes cleaner which is an important advantage. By locating the electric
motor driven pump set in a safe place into which the explosive dust laden air has absolutely no access, the
whole arrangement could be made safe. This system could be used to great advantage in hot and dry
atmospheres as cooling of air is also automatically obtained and hence the inside space gets conditioned
somewhat. The smaller units using Khas Khas screens are popularly called as desert coolers and could be
used in explosive buildings by incorporating improvements to the electrical system and using a motor of
higher specification (flameproof, dust-tight etc.) for driving the pump.
44. Dehumidification involves the withdrawal of moisture from the air to lower its relative humidity. This
generally becomes necessary during wet monsoon months to facilitate production processes and prolonging
storage life of explosives.
45. Dehumidification is achieved mainly by the following two ways:
(a) By excessive cooling of air by the air-conditioning plant to condense out moisture and then reheating
the air to the desired level to reduce its relative humidity. This system can yield relative humidity above 40
to 45%. Subsequent reheating of air is achieved by electric strip heaters, by steam or hot water coils.
Several electric strip heaters are installed in the air-handling unit or in the supply air duct near to the air-
handling unit and they are energized in stages by an automatic contractor (Fig. 8). The electric strip heaters
have the inherent danger of attaining excessively high temperatures and risk of short circuiting. Also the
electric cabling needs constant attention to ensure proper contact and continuity. In view of these factors,
electric strip heaters are NOT considered suitable for use in explosive buildings. They should not be used
except in exceptionally safe cases adopting maximum safety precautions. Heating by hot water coil is safer
than heating by steam coil, but the coil size is likely to be bigger. A hot water or steam boiler together with
all accessories becomes necessary. However, any one of these heating coils could be used for reheating of
air. Reference should be made to IS: 659-1964 „Safety Code for Air Conditioning (Revised)‟ for
information about heating.
(b) By chemical dehumidification using adsorbents: Moisture can be withdrawn from air by passing it over
a desiccant that has affinity for water vapour. When moisture is absorbed by the desiccant, latent heat is
liberated which elevates the air temperature. Thus the air after the drying process attains a high
temperature, in most cases exceeding 40 0C (104 0F) which would be unacceptable in explosive building.
Hence the dried air has to be subsequently cooled before being admitted into the conditioned space. This
cooling is best achieved by air-conditioning; alternatively by a cooling water coil through which circulation
of ordinary water is kept up by a pump. The desiccant needs frequent reactivation which is achieved by
blowing hot air over its surface to evaporate the trapped moisture. By chemical dehumidification, relative
humidity as low as 10% can be achieved. Chemical dehumidifier models have electric motors, heater,
blowers, time switches, relays and contacts electric wiring etc. inbuilt in them. Generally these are of
normal specifications quite unsuitable for use in explosive buildings and will have to be replaced by those
with higher specification (like flameproof, dust-tight, etc.) before the unit as a whole can be considered safe
for use in explosive buildings. Hence before deciding on using any model of chemical dehumidifier, its
constructional details and specifications should be critically examined from safety angle and changes
effected wherever necessary. Chemical dehumidifiers consume considerable electric power. Wherever very
low relative humidity is aimed at, careful note should be taken of the generation of static electricity in dry
atmospheres.
Reducing Relative Humidity
46. In the dehumidification processes considered above; lowering or relative humidity is achieved by
reducing the moisture content of the air. However, relative humidity can also be lowered by raising the air
temperature without extraction of moisture from it. Heating could be done by electric strip heaters, steam
or hot water coils or even by infra-red lamps, The relative merits of electric/steam/water heating have been
given in para 44 (a) above. Infra-red rays provide heating by radiation and are NOT safe or convenient for
the purpose under consideration. Reducing relative humidity by heating alone appears to be an attractive
proposal due to its simplicity and low cost, However; this method could be acceptable during winter
months; but during monsoon months, the extent of heating involved to lower the relative humidity will
result in a much higher temperature in the conditioned space than the ambient temperature and will create
uncomfortable working conditions. Hence this method is NOT acceptable in case of explosive buildings.
Controls used in Air Conditioning
47. The common controls used in air-conditioning are the following:
(a) Low pressure and high pressure safety controls – used for stopping the compressors in case of very low
pressure (vacuum) or excessively high pressures developing in the refrigerating system (see clause 2
“Terminology” in IS: 60-1963” Safety Code for Mechanical Refrigeration”)
(b) Thermostat control – for maintaining desired inside temperature in the conditioned space.
(c) Humidistat – for maintaining desired humidity in the conditioned space,
(d) Automatic contactors for pre-heaters – for energizing the heaters in stages to reheat the supply air to the
required temperature.
48. All these controls are electrically operated, mostly on 220 volts, and have electric make and break
contacts. During operation, sparking at the contacts is inevitable which could prove extremely dangerous is
case of explosives buildings. Therefore selection of the location for installing the controls should be done
with utmost care.
49. The low pressure and high pressure cut-outs, and the automatic contactors for heaters, are generally
location in the compressor room portion of the air conditioning plant room (see Fig. 1 and 4). Explosive
vapours and dust do not have access to this region. Therefore the operation of these controls does not pose
any danger.
50. The thermostat for temperature control is actuated by a thermostatic bulb and long capillary tube
arrangement. Thus the temperature control as such containing the electric contacts could be located in the
compressor room portion of the plant room and only the probe portion of the control extended into the
weather-maker room, Since the explosive vapour/dust does not have access into the compressor room, the
operation of the thermostat control does not pose any danger. In case the thermostatic control operates the
refrigerant solenoid valve (where provided), the refrigerant solenoid valve should also be located in the
compressor room portion of the plant room. The main point to ensure is that explosive vapour / dust should
not have any access to the thermostat control, which therefore will have to be located in an uncontaminated
safe place. In chilled water systems, the thermostatic control could be located in the compressor room and
will pose no problem.
51. The humidistat used in air-conditioning has been of imported origin. The common type works on the
sensitivity of hair elements. The hair element is humidity conscious and actuates the electric contacts
through leverages and springs. The whole assembly is a compact unit and for efficient operation, the hair
element has perforce to be kept in the air shower whose humidity condition it is to sense. Thus the obvious
location for this humidistat unit is in the return air path inside the weather-maker room. When flammable
or explosive vapour/dust is present in the return air, the sparking at the electric contacts during make or
break operation will prove disastrous. There is no possibility of quenching the spark or isolating the electric
contacts from the hair element assembly so that the contact could be located in a safe atmosphere.
Therefore, this type of control is definitely NOT safe for use with air-conditioning system of explosives
process/laboratory buildings. The utility of this control for air-conditioning systems of explosives storage
buildings is also in serious doubt and therefore it is best to avoid use of this control. One particular model
of explosion proof humidistat considers safe for use in hazardous buildings is available from M/s Bry Air.
Alternatively, the other solution is to omit the humidistat control altogether and operate the plant manually,
guided by periodic readings of dry/wet bulb temperatures inside the conditioned space. This calls for skill,
experience and dedication on the part of the plant operators. To help matters, the maximum relaxation in
relative humidity drift should be permitted by the Users.
52. Some firms are at present engaged in developing and perfecting electronic humidistat control. Until full
technical details are available and their performance established, no firm comments could be offered about
their suitability for use in air-conditioning systems of explosive buildings.
Refrigerants and Effect of Fires
53. Modern air-conditioning plants work with refrigerants from the Freon family and they are Freon-11,
Freon-12 and Freon-22. Ammonia is also sometimes used in cold temperature installations (but rarely in
modern air-conditioning plants).
54. The Freon group is neither flammable nor explosive and hence is considered as a safe refrigerant.
Ammonia is considered to be moderately flammable and forms an explosives mixture with air when
present in the right proportions.
55. When fire occurs nearby, radiant heat reaching the air-conditioning plant can generate high pressures
inside the system. This could cause leakage of refrigerant through safety valve or pipe rupture, If Freon is
the refrigerant, then it may decompose into toxic gases in contact with fire. In case of ammonia, the fire
may increase in violence or an explosion may take place. For these reasons, the area around the plant room
should be free of all combustible materials and such materials should not be stored in the plant room. In
case of fire, the air-conditioning plant should be shut down following the correct procedure and a vigil
maintained to detect refrigerant leakage or other ill effects.
56. As regards Fire Alarm and fire fighting system, the users shall obtain the recommendations of the Fire
Adviser to Ministry of Defence.
General Considerations for Air-conditioned Explosives Buildings
57. Technical requirements for the construction of explosives storages are given in STEC pamphlet No. 3.
Explosive building intended to be air-conditioned deserve extreme care and attention during
planning/design stages. Reliable and continuous air-conditioning service is extremely vital for the well
being of the occupants. Serious consideration is, therefore, necessary for the provision of stand-by units/air-
conditioners, spare blower and motor and adequate/ample spares.
Air-conditioning Plant Room
58. The plant room for housing the central type of air-conditioning plant could be imagined to comprise of
the compressor room and the weather-maker room (see Figs. 1 & 4). The preliminary considerations
regarding the possible locations of this plant room with respect to the main air-conditioned building would
be as follows:
(a) Single building, Untraversed.
Plant room attached to the building.
Advantages:
(i) Simple direct expansion system
(ii) Least ducting, Less danger from dust accumulation. Easy Cleaning.
(iii) Least cost.
Disadvantages:
(i) Plant operators exposed to danger.
(ii) Loss of plant inevitable in case of accident.
(iii) Fire/accident in plant room is more likely due to equipment in it and this can easily spared to
main building.
(b) Single building, Un-traversed, Plant room beyond PIQD, but weather-maker room attached to the
building.
Advantages:
(i) Plant operators quite safe.
(ii) Plant safe in case of accident.
(iii) Least ducting: Less danger from dust accumulation. Easy Cleaning.
Disadvantages:
(i) Chilled water system costlier.
(ii) Air-handling unit performance difficult to monitor,
(c) Single building, traversed.
Plant room outside traverse.
Advantages:
(i) Plant operators relatively safe
(ii) No increase in traverse length
(iii) Simple direct expansion system
(iv) Very suitable for all fresh air system
(v) Plant safe in case of accident
Disadvantages:
(i) Long duct. More initial cost, increased dust collection, difficult to clean.
(ii) If duct runs through traverse, it will weaken it.
(iii) Rather inconvenient for re-circulated air system.
(iv) Separate lightning protection required for plant room.
(d) Single building, traversed.
Plant room attached to the building.
Advantages:
(i) Simple direct expansion system.
(ii) Least ducting. Less danger from dust accumulation Easy cleaning.
(iii) Low cost.
(iv) Lightning protection may NOT be required for plant room.
Disadvantages:
(i) Plant operators exposed to danger.
(ii) Loss of plant inevitable in case of accident.
(iii) Increase in traverse length. Very costly.
(iv) Fire/accident in plant room is more likely due to equipment in it and this can easily spread to
the main building.
(e) Single building, traversed.
Plant room beyond traverse, but weather-maker room attached to the building and inside the traverse.
Advantages:
(i) Plant operators relatively safe.
(ii) Plant safe in case of accident.
(iii) Least ducting. Less danger from dust accumulation. Cleaning easy.
(iv) Very suitable for re-circulated air system.
Disadvantages:
(i) Chilled water system costlier.
(ii) Marginal increase in traverse length.
(iii) Air-handling unit performance difficult to monitor.
59. The above preliminary considerations reveal that, for a small increase in initial cost, the chilled water
system is the most suitable arrangement. The important advantages gained are the requirement of least
ducting and suitability for both re-circulated and all fresh air systems. It becomes evident that, with the
plant room outside the traverse as shown in (c) above, use of direct expansion system will be inconvenient
because ducting will be a major problem which becomes worse with recirculated air systems (as the return
duct size in very considerable). The arrangement shown at (d) above, being similar, suffers from the same
disadvantage. If the plant room is attached to the main building as shown in (a) and (e) above, then the
element of risk is somewhat enhanced because of the dangers associated with electric power consuming
apparatus machinery and their proximity to the explosive materials in the main building. Sometimes even
physical constraints like insufficient space/land influence the location of plant rooms.
Plant Room Location and Type of Air-conditioning System
60. The factors involved in locating the plant room and selecting the type of air-conditioning system are
somewhat inter-dependent and demand careful consideration. All decisions should be towards ensuring
safety from fire hazard, because the building will contain explosives and the plant room will have
electrically operated machinery/controls. Incidence of fire in any one of them, which is very much possible,
will pose danger to both of them simultaneously. Use of a simple, reliable air-conditioning plant with
minimum ducting is definitely a step towards safety.
61. Locating the air-conditioning plant room or even the weather-maker room inside the air-conditioned
building is not recommended.
62. In case of Categories „A‟ and „B‟ buildings, the air-conditioning system shall be of chilled water type.
The plant room shall be located beyond the traverse or PIQD and the weather-maker room shall be near to
or even attached to the conditioned building. When attached, the wall separating the weather-maker room
from the building shall be a brick or RCC wall of specified thickness.
63. In the case of small, traversed Category „A‟ buildings, the air-conditioning system could be of the
direct expansion type. The plant room (including the weather-maker room) could be located outside the
traverse.
64. In the case of small, traversed Category „B‟ building, the air-conditioning system could be of the direct
expansion type. The plant room (including the weather-maker room) could be attached to the conditioned
building, in which case the wall separating them shall be a brick or RCC wall of specified thickness, or
could be located conveniently near to the conditioned building inside the traverse.
65. In the case of Category „C‟ building, chilled, water type of air-conditioning plant is preferred in
comparison with the direct expansion system, but is NOT essential. With chilled water system, the plant
room could be located beyond the traverse or PIQD and the weather-maker room located near to or even
attached to the conditioned building. When attached, the wall separating the weather-maker room from the
building shall be a brick or RCC wall of specified thickness.
66. In the case of small, traversed or un-traversed Category „C‟ building, the air-conditioning system could
be of the direct expansion type. The plant room (including the weather-maker room ) could be attached to
the conditioned building, in which case the wall separating them shall be a brick or RCC wall of specified
thickness, or could be located conveniently near to the conditioned building (inside the traverse, if
provided).
67. In very exceptional cases, package type air-conditioners housed in a separate room and using air ducts
could be provided in case of Category „C‟ building if the safety aspects are not compromised and always
with the prior concurrence of STEC.
68. In case of buildings with several internal bays/rooms to be air-conditioned, safety demands that the
individual bays/rooms be separately served by the air-conditioned plant to eliminate the risk of fire
spreading from one place to another through the air ducts. Where this is practically not feasible, grouping
of bays/rooms could be resorted to with major accent placed on safety. If direct expansion system becomes
a cumbersome arrangement, chilled water system with a adequate number of air-handling units should be
used.
69. When a group of buildings are to be air-conditioned, chilled water system shall be used. The plant room
shall be located beyond the PIQD if the buildings are un-traversed or beyond the traverses when the
buildings are provided with them. Each building shall be served by its own weather-maker unit (s) which
shall be housed in weather-maker room (s) attached to the building and separated by a wall of specified
thickness or located conveniently near to the buildings.
70. In all cases considered above, the weather-maker room shall have the same specifications as the air-
conditioned buildings served by them. All electrical items in the weather-maker room (s) shall be of same
category/specifications as adopted for those in the conditioned buildings.
Summary
71. Air-conditioning and its allied services are finding an important application in the explosives
manufacturing and storage activities. Now-a-days the requirements are varied and are becoming
increasingly stringent with the advancements in modern technology. The air-conditioning system adopted
could be anything from the simplest to the most complicated type supported by several adjuncts to fulfill its
roll. In view of the complexity of the equipment involved in this service, every equipment should be
subjected to a critical examination from safety angle to establish its suitability at the time of incorporation
in the works.
72. In order to ensure requisite safety, the following factors should always be borne in mind in respect of
air-conditioning service:
(a) Furnishing correct and complete information by the actual users (as given in proforma at Appendix „A‟)
(b) Correct design, planning and construction of the conditioned building and the plant room.
(c) Correct selection of type and system corresponding to air-conditioning, winter heating or
humidification/dehumidification.
(d) Critical examination of every equipment used in the installation from safety angle.
(e) Correct selection and incorporation of safety gadgets/aids and fire alarm/fighting system.
(f) Ensuring punctuality in preventive maintenance, repair and replacement schedules.
(g) Ensuring reliable and continuous air-conditioning service.
(h) Training the plant operators to be duty and safety conscious at all times.
(j) Ensuring cleanliness in and around the building and plant room.
(k) Inculcating orderly working habits in the occupants of the building and plant room.
ASSESSMENT OF THE NEED FOR LIGHTNING PROTECTION
1. As a general rule, lightning protection should be provided during construction of all new facilities to be
used for the storage or maintenance of ammunition and explosives. There may be certain situations
involving either new construction or existing facilities where the installation of lightning protection
systems is unwarranted. When making a determination as to whether or not lightning protection should be
installed, consideration should be given to the following factors :
(a) Does the structure itself afford sufficient protection without further installation?
(b) Are the explosive properly sited, so that an explosion will not endanger exposed sites?
(c) Does the frequency of electrical storm; e.g. five or more per year, justify the installation?
(d) Are people physically located in the structure with the ammunition and explosives?
(e) Can the loss of the ammunition and explosives be tolerated?
(f) In case of an existing structure, does the value of the content, warrant the cost of an installation?
General
2. (a) The principle of protection against the effects of lightning discharges is to provide a conducting path
between the atmosphere above a structure and the general mass of earth so that the discharge can pass to
earth with the minimum risk to the structure, its contents and occupants.
(b) It is essential that bay system of protection and the means of fixing it should be effective, simple,
rugged, accessible and permanent. This applies particularly to earth termination networks which are hidden
from view.
(c) So many factors, such as quantity-distances, terrain, and access roads have to be taken into account
when planning an explosives area, that lightning protection may be given n difficulty in obtaining a suitable
resistance to earth.
Selection of Materials
3. (a) The selection of materials for the system should take account of their compatibility
and corrosion problems etc. Generally metals should be chosen which are close in
the electrochemical series in order to reduce the risk of electrolytic interaction.
(b) Where the possibility of significant electrolytic action exists, dry sealed metallic joints should be used
to provide adequate protection.
(c) Aluminum is generally satisfactory but it should be joined to copper by dry sealed joint and it should
not be used in direct contact with soil.
(d) Conductors for use as suspended air termination n networks should be stranded and of hard drawn
aluminum, hard drawn copper, or copper coated steel. The number and nominal diameter of wires in the
conductor should not be less than 4/7/4.30 mm for aluminium conductors, 7/3.55 mm for copper
conductors, and 7/2.05 mm for copper coated steel conductors.
Component Parts
4. The main component parts of a lightning protection system are:
(a) Air termination network.
(b) Down conductor.
(c) Earth termination network.
(d) Test joint.
(e) Bond
Air termination Network
5. There are three forms of air termination network for a system:
(a) Fixed air termination network
(b) Suspended air termination network
(c) Vertical air termination network
The three basic forms are shown in Figures 1 to 2 and a variation of the fixed air termination network (the
integrally mounted system) is shown in Figure 4.
Fixed Air Termination Network 6.
(a) The roof conductor should be in the form of a mesh having sides not greater than 7.5m. However, on a
concrete roof having reinforcement metal bonded to the lightning protection system, the mesh may be
increased to 10m. When unusually sensitive explosives are held at the site, the mesh should be reduced to 5
m.
(b) Each conductor should be supported on “stand-off hold-fasts” or a small concrete block; it should not
be fixed directly to the surface of the roof. As the edges are generally the most vulnerable parts of the roof,
each conductor should be positioned as close to the edge of the roof as practicable, but in no circumstances
more than 0.3 m from the edge.
(c) Each roof conductor should be fixed above the level of any up stand such as a canopy over a doorway.
(d) Where a building has roofs at different levels (ie where there is a tank room on the main roof) each one
should be protected. Where the fixed air termination network of a roof at one level affords complete
protection to a roof at a lower level, a separate conductor on this roof is not necessary. Where the fixed air
termination network of a roof at one level, afford partial protection to a roof at a lower level, then only the
unprotected part of the lower roof needs a separate conductor.
(e) There is no requirement to provide pointed conductors or vertical finials on a fixed air termination
network.
(f) A variation of the fixed air termination system is the integrally mounted system. The important
differences in this variation from the system described above are the requirements for metallic pointed
conductors and the spacing of the conductors. This system is an acceptable alternate for the fixed air
termination system.
FIG 1
DIMENSION „A‟
EXTREME CONDITION 5.0 m
NORMAL 7.5 m
METAL BONDED ROOF 10.0 m 7 8
Suspended Air Termination Network
7. (a) A suspended air termination network comprises of two or more poles supporting and bonded to an aerial
conductor or several conductors.
(b) A supporting pole should be positioned at least 2 m from the site. When a pole consists of a non-conducting
material, a conducting tape should be provided to bond the aerial conductor to the earth termination network
and any stay wire should be bonded to both ends of this tape. In the case of a metal pole, any stay wire should
be bonded to both ends of this pole.
(c) To prevent flash-over, the minimum clearance between the lowest part of an aerial conductor and the site it
protects, should not be less than 7 m in the maximum sag condition, i.e. snow and ice.
Vertical Air Termination Network
8. A vertical air termination network comprises of a single, metallic pole positioned at least 2 m from the site.
Any stay wire should be bonded to both ends of the pole. The height of the pole should be such as to ensure a
zone of protection of at least 300 or 600.
Integrally Mounted System
9.
(a) The integrally mounted system consists of metallic pointed conductors, at least 0.6 m in height, which
should be securely mounted on roof ridges, parapets and around the perimeter on flat roofs, spaced not more
than 7.5 m apart. Where it is necessary to exceed this spacing, the height of pointed conductors should be
increased 5 cm for each 0.3 m increase over 7.5 m. On large flat or gently sloping roofs, pointed conductors
should be placed at the points of the intersection of imaginary lines dividing the surface into rectangles having
sides not exceeding 15 m in length. Pointed conductors should be provided with at least two paths to earth.
(b) There should be no less than two down conductors on every building.
(c) Where an electrically continuous path can be assured by bonding or manner of construction, then metal
roofs, metal walls, steel framework, and reinforcing rods (in concrete structures) may serve in lieu of all or
portions of normally required down conductors.
(d) Earth-covered magazines may be protected with an integrally mounted system by mounting one pointed
conductor on the top of the front wall and one on the ventilator in the rear.
Faraday Cage
10. The optimum scheme for protecting extremely sensitive operations from all form of electromagnetic
radiation is to enclose the operations or facility inside a Faraday cage. However, the Faraday cage is difficult to
construct and economically justified only for “one of a kind” facilities that are essential or when extremely
sensitive operations warrant the level of protection it provides. The Faraday cage affords excellent protection
from lightning. Effective lightning protection is provided in a similar manner by metallic enclosures such as
formed by the steel arch and reinforcing bars of concrete end walls and floors of steel arch magazines and the
reinforcing steel of earth-covered magazines constructed of reinforced concrete.
Down Conductors 11. Where a system of fixed air termination network is adopted, at least two down conductors should be
provided around the perimeter of the site, equally spaced so far as is possible, at intervals, not exceeding 15 m.
Each down conductor should be connected to an earth termination network via a test joint.
Earth Termination Network and Earth Electrodes
12. (a) Earth termination networks are to be provided as close as practicable to the building being protected, but
no closer than 0.6 m from the wall footings. An earth termination network is to consist of earth electrodes, of
rods, tapes or other means of providing a connection with the general mass of earth.
(b) Where rod electrodes are used they are to be driven to the depths necessary to give the desired earth
resistance; the minimum depth being at which the rod penetrates into soil of constant dampness. Where more
than one rod is necessary to obtain the required resistance, the spacing between the rods is to be at leas equal to
the driven depth.
(c) In difficult ground conditions where rod electrodes prove ineffective, e.g. in areas of deep gravel or areas
having little soil cover, the use of radial type of electrodes should be considered. These comprise copper tapes
laid in a trench 0.5 m deep, one tape per trench, and the trench back filled with sifted earth. The length of the
radial electrodes is that, which gives the required resistance.
(d) When a building is sited on bare rock, a satisfactory earth electrode can usually be obtained by rock drilling
and back filling the hole with sifted earth or a mixture of carbon powder and copper dust before driving the
earth rods,. Any diameter of hole, 75 mm or greater, will usually be sufficient. Coke or fly ash must not be used
as back fill, owing to their corrosive effect on copper.
(e) Water pipes or other services should not be used as part of the earth termination network system, or as the
earth electrode.
(f) To allow for the isolation of the electrode during testing, the upper end of the electrode must terminate in a
small pit.
(g) All earth electrodes of a system must be interconnected by a ring conductor. This ring conductor is to be
buried at a nominal depth of 0.5 m below ground, unless conditions such as the need for bonding metal forming
part of the building make it desirable to have the ring exposed. The earth systems of adjacent structures should
be interconnected where reasonably practicable and where the ground conditions make the achievement of the
required earth resistance difficult.
(h) When exposed, the ring conductor is to be attached to and encircle the building at a nominal height of 0.5 m
above ground level. It is to pass through and be connected to each test joint of the system. The ring conductor,
when attached to the building, is to be visible through its entire length, except that where paths and roadways
make it necessary for the conductor to go underground, it may be drawn into a non-metallic pipe. (The ring
conductor should not go over the top of a door opening, but should go underground as described).
Test Joint
13
(a) A multi-way, clamp type test joint should be properly constructed on each down conductor and each
supporting pole, at about 0.5 m above ground level. Only the earth termination networks should be permitted
below a test joint.
(b) A test joint on a supporting pole should be connected to an earth termination network, and any stay wire at
points as near as practicable to the pole.
Bonding of Structural Metal 14.
(a) All major items of metal on, or forming part of, a building or structure should be bonded to the lightning
protection system. The welding of metal reinforcement bars to from part of the lightning protection system is
not required, since the stirrup tie wires provide adequate bonding between bars. The roof reinforcement should
be brought out, in at least two diagonally opposite places, and at each down conductor position, in order to be
bonded to the fixed air termination network and appropriate down conductor. Where a down conductor is
attached to a reinforced concrete column or a concrete-reinforced steel column, the steel work should be
connected to the down is not contiguous with the reinforcement of the roof, an additional connection to the
reinforcement or steel work columns other than those described above; nor for lengths of metal less than 2 m
(i.e. metal window frames), metal ventilators and metal fittings provided they are not within 0.3 m from a
conductor.
Bonding of Services
(b) The metal sheath or armour of the incoming electrical supply cable should be bonded to the lightning
protection system at the point of entry to the main switch, which should itself be bonded. Additionally, the
metal sheath or conduit of each circuit leaving the main switch or distribution board should be bonded to the
lightning protection system at the point of entry. All straight runs of metallic conduit, pipe work or metallic
cable sheathing in excess of 15m should be bonded at both ends to the lightning protection system.
Bonding of Rails for Cranes
(c) The rails of all cranes within a building should be bonded at each end to the lightning protection system. The
resistance when measured between the crane and the crane rails must not exceed 1 ohm under worst conditions
of crane loading. Furthermore rails which extend beyond the building should be bonded to the lightning
protection system at the point of entry.
Electrical Conductance
15. Lightning protection systems should conform to the following requirements
(a) With all connections removed, the resistance to earth of each earth termination network should not exceed
10 ohms multiplied by the number of earth electrodes comprising the system.
(b) Exceptionally, where a buried ring conductor is provided to improve the earth resistance, this ring conductor
may be considered as part of the earth termination network. In such circumstances, with all earth electrodes
connected to the ring conductor, the resistance to earth should not exceed 10 ohms.
(c) With all earth electrodes connected to the system and all extraneous bonding removed, the resistance to earth
of a system when measured at each point approximately equidistant between earth electrodes should not exceed
10 ohms. (The removal of all extraneous bonding should be undertaken only for acceptance testing).
Steel framed Structure
16. A steel framed structure with cladding such as asbestos sheet may be regarded as self-protecting provided
that the resistance to earth of each stanchion does not exceed 10 ohms. This measurement should be made
before the electricity supply cable or by metallic service pipe is attached to the structure. Where these
conditions of resistance are not met, a ring conductor, bonded to each stanchion and with earth electrodes at
each end of the structure, should be provided.
Earth-Covered Building
17. An earth-covered building should be protected against lightning in accordance with the above principles
subject to the following requirements:
(a) Any roof conductor may be fixed directly to the roof of the building without the use of “stand-off hold-fasts”
or concrete blocks.
(b) The ring conductor should run underground at a distance of 1 m from the toe of the earth-cover. It may
however be taken across the head-wall, or other wall not covered with earth, at about 0.5 m above ground level.
(c) A down conductor should pas through the earth-cover at a distance of about 0.5 m from the structure. It
should however be taken down the head-wall, or other wall not covered with earth, and similarly run down the
top of any wing-wall.
(d) The joint between a down conductor and either a roof conductor or an earth termination network should be
readily accessible for inspection pit with a cover.
Risk Assessment and Recommendations for the Selection of Lightning Protection Systems 19. In addition to the guidance provided in this pamphlet, for other aspects like engineering design, material
selection, construction, fabrication and code of practice for laying the system, BIS standard No. IS 2309/1089
on the subject should be consulted.
Annexure
TERMINOLOGY
1. The following definitions are used in connection with protection against lightning:
(a) Air termination Network
The part of a lightning protection system that is intended to intercept lightning discharges.
(b) Bond
A conductor intended to provide electrical connection between the protective system and other metal work.
(c) Cone of Protection
The space coverage provided by a vertical conductor.
(d) Down Conductor
A conductor which connects the air termination network with the earth termination network
(e) Earth Electrode
The portion of the earth termination network which is deigned to provide direct electrical contact with the
general mass of earth
(f) Earth Termination Network
The part of the lightning protection system which is intended to discharge lightning currents into the general
mass of earth. all parts below the lowest test joint in a down conductor are included in this term.
(g) Joint
The junction between portions of the lightning protection system
(h) Ring conductor
The ring conductor is that part of the earth termination network which connects the earth electrodes to each
other or to the down conductors.
(j) Test Joint
A joint designed and situated to enable resistance or continuity measurements to be made.
(k) Zone of Protection The zone considered to be protected by a complete air termination network.
