TRCI - Bundesamt für Umweltschutz

TRCI-2009Publisher BCI Basle Chemical Industry Edition: 2009 replaces: Edition 2001
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TRCI Edition 2009 Tank Farm Guidelines for the Chemical Industry
Preface to the 2009 The TRCI Guidelines of 2001 had to be reviewed since the VWF (Ordinance for the Protection of Water from Potentially Water-Polluting Liquids) was withdrawn. Instead of the VWF, two enforcement regulations of the KVU (Conference of the Heads of Environmental Protection Offices in Switzerland) are now applicable. The review also updates the entire document and restructures it. The TRCI Guidelines are applicable to storage facilities and plant tank farms in the chemical and pharmaceutical industry. They are applicable to liquid chemicals and can also be used for plant facilities in an analogous manner. They are listed as Engineering Rules by the Swiss Federal Office for the Environment (BAFU). The guidelines are obligatory for the design of storage facilities in the BCI, they serve as a supplement to the provisions and directives of the authorities. A team of experts from CIBA, CLARIANT, HOFFMANN-LA ROCHE, HUNTSMAN and LONZA reviewed the TRCI Guidelines for the BCI. All rights reserved © Copyright 2009 by BCI/TRCI The TRCI Guidelines are available in German, French and English via: http://www.bafu.admin.ch/tankanlagen
TRCI Edition 2009
1.2 Purpose and scope of application.................................................................................... 6
1.3 Conditions for the operation of tank farms according to TRCI ...................................... 6
1.4 Water pollution control areas, ground water pollution control zones and water pollution control measures ....................................................................................................................... 7
1.5 Classification of liquid chemicals ................................................................................... 7 1.5.1 Water pollution control.......................................................................................... 7 1.5.2 Fire protection........................................................................................................ 7 1.5.3 Air pollution control .............................................................................................. 8
2.1 General comments........................................................................................................... 9 2.1.1 Site selection and assessment of construction site................................................. 9 2.1.2 Planned arrangement ............................................................................................. 9 2.1.3 Tanks in underground concrete spaces ................................................................ 11 2.1.4 Filling points and drum filling points .................................................................. 11
2.2 Tank and protective clearance....................................................................................... 12 2.2.1 Outdoor storage tanks and drum storage ............................................................. 12 2.2.2. Storage tanks in buildings.................................................................................... 15 2.2.3 Outdoor filling points and drum filling points..................................................... 16
3 Protective structures, foundations..........................................................17
3.3 Foundations................................................................................................................... 20
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4 Storage tanks and equipment .................................................................21
4.1 Storage tanks ................................................................................................................. 21 4.1.1 General comments, terms .................................................................................... 21 4.1.2 Storage tanks of metal ......................................................................................... 22 4.1.3 Storage tanks of plastics ...................................................................................... 23 4.1.4 Heating and cooling systems ............................................................................... 23 4.1.5 Inert gas blanketing ............................................................................................. 23 4.1.6 Tank surface coating............................................................................................ 24 4.1.7 Thermal insulation............................................................................................... 25
4.2 Piping ............................................................................................................................ 26 4.2.1 General comments, terms .................................................................................... 26 4.2.2 Requirements of piping ....................................................................................... 26 4.2.3 Design, installation .............................................................................................. 26 4.2.4 Connection of pipes to tanks and tankers ............................................................ 27 4.2.5 Hoses ................................................................................................................... 27 4.2.6 Gas balance, pressure compensation lines........................................................... 27 4.2.7 Overspill, overflow equipment ............................................................................ 28 4.2.8 Distributing and return lines ................................................................................ 28 4.2.9 Testing of piping.................................................................................................. 28 4.2.10 Pipe insulation ..................................................................................................... 28
4.3 Valves and fittings ........................................................................................................ 29 4.3.1 General comments ............................................................................................... 29 4.3.2 Shutoff valves ...................................................................................................... 29 4.3.3 Vent valves .......................................................................................................... 29 4.3.4 Flame arresters..................................................................................................... 29
4.4 Pumps............................................................................................................................ 31
5 Ecology, safety and fire protection .........................................................34
5.1 Displacement and breathing losses ............................................................................... 34 5.1.1 Displacement losses............................................................................................. 34 5.1.2 Breathing losses ................................................................................................... 34 5.1.3 Measures to prevent or reduce emissions ............................................................ 35
5.2 Liquid losses ................................................................................................................. 36
5.4 Fire and explosion protection........................................................................................ 38
5.4.1 General comments ............................................................................................... 38 5.4.2 Definition, terms.................................................................................................. 38 5.4.3 Alarms ................................................................................................................. 39 5.4.4 Outdoor fire protection measures ........................................................................ 39 5.4.5 Protective measures in buildings ......................................................................... 42 5.4.6 Protective measures in electrical rooms .............................................................. 42
5.5 Earthquake safety .......................................................................................................... 43
6.2 Obligations of the sponsorship or construction management ....................................... 44
6.3 Operating permit ........................................................................................................... 44
6.6 Existing facilities and facility parts............................................................................... 47
7.1 Minimum dimension of sealed pavings at transfer sites ............................................... 49
7.2 Air pollution control (limit values) ............................................................................... 51
7.3 Test procedures for facility parts .................................................................................. 52
7.4 Leakage testing of protective structures........................................................................ 53
7.6 Precautions against the hazardous effects of electric current ....................................... 55
7.7 Protection indices (to determine min. fire protection measures) .................................. 56
7.8 Calculation of the required quantity of cooling water .................................................. 57
7.9 Tank farm design terms................................................................................................. 65
7.11 Abbreviations ................................................................................................................ 69 7.11.1 Abbreviations for authorities, regulations, specialist agencies, etc. .................... 69 7.11.2 Technical abbreviations....................................................................................... 70 7.11.3 Material abbreviation........................................................................................... 70
1 General information 1.1 Introduction The TRCI are to be applied to the construction and operation of facilities for the storage and transfer operations of liquid chemicals. They take into account the specific requirements of the chemical industry and are mainly based on - the federal law governing environmental protection (Environmental Protection Act [USG])
[3]; - the Swiss Water Protection Act (GSchG) [1] and pertaining regulations; - Ordinance for the protection against accidents (Accident Ordinance, StFV) [7]; - Enforcement regulations and guidelines of the KVU [34 and 35]; - Clean Air Ordinance (LRV) [5]; - SUVA Bulletin 2153, Explosion Protection: Principles, minimum provisions, zones [16].
The TRCI only takes into account regulations, which are valid throughout Switzerland. Depending on the location of the facilities, any special Cantonal or local regulations are also to be taken into account. Any deviation must be agreed during the plan approval procedure. The Engineering Rules are to be adhered to on principle (KVU [34-05]). Chapter 7.10 contains a summary of the basic documents.
1.2 Purpose and scope of application The TRCI are applicable to storage facilities and plant tank farms of the chemical and pharmaceutical industry. They take into account facilities used for storing and transfer of liquid chemicals (tanks and drums with a usable volume above 20l). They only ensure adequate safety when they are applied in their entirety and serve, in particular - the protection of watercourses - fire protection - air pollution control - labour protection (personal protection)
The TRCI may also be applied to plant facilities in an analogous manner. The TRCI do not cover the following items - Storage and transfer of liquid fuels (see CARBURA guidelines [8]; - Liquified gases (SUVA [16]) 1.3 Conditions for the operation of tank farms according to TRCI Location: Tank farms are to be installed within an enclosed and supervised area. Tank farms for
flammable liquids may only be installed in an area for which a fire brigade trained to deal with chemical hazards is responsible;
Operation: The operation of storage facilities must be registered or approved, on principle (see Chap. 6);
Safety: Tank farms are to be equipped with safety devices according to Chap. 5; Maintenance and Inspection: Tank farms must be maintained and inspected according to Chap. 6; Register: The operator has to keep a register on storage facilities with potentially water-
polluting liquids.
1.4 Water pollution control areas, ground water pollution control zones and water pollution control measures
Switzerland is divided into water pollution control areas, ground water pollution control zones and ground water pollution control sites with regard to water pollution control measures to be applied (see GSchV Art. 29 and 31 [2]). The principles of handling potentially water-polluting liquids are stated in the Water Protection Act (Art. 22 ff. GSchG [1]) and provisions concerning facilities with potentially water-polluting liquids in particularly endangered water pollution control areas are contained in the GSchV (Art. 32 and 32a as well as Appendix 4, Items 21, 22 and 23). Water pollution control measures outside of ground water pollution control zones and sites (see also KVU [35-1.1]): These include - Prevention of liquid losses; and, depending on the storage facility and the transfer point, - the easy detection of liquid losses or - the easy detection and retention of leaking liquids are demanded. Water pollution control measures in ground water pollution control zones and sites: In relation to the pollution control measures stated above, respective pollution control measures are to be implemented for facilities permitted in ground water pollution control zones and sites which ensure that liquid losses are easily detected and leaking liquids are completely retained. Industrial and commercial operations emanating a danger for ground water are not permitted (see GSchV Art. 29 and 31 [2]). 1.5 Classification of liquid chemicals All liquid chemicals are classified according to the aspects listed below.
1.5.1 Water pollution control Furthermore, the GSchV differentiates between liquids which can pollute water in small quantities and other potentially water-polluting liquids. Correspondingly, the potentially water-polluting liquids are divided into two classes in relation to their properties according to KVU [35-4]: - Class A: if they can change water adversely in small quantities; - Class B: if they can change water adversely in large quantities.
In mixed storage, the measures are in line with liquids of Class A. A list of classified liquids issued by BUWAL (now BAFU) [4] is to be observed. Class 1 of the 1999 list corresponds to Class A today and Class 2 to Class B. 1.5.2 Fire protection The classification of liquids for fire protection purposes is based on the degree the fire hazard as represented by the flash point (according to VKF [Association of Cantonal Fire Insurance Companies], Fire Protection Guidelines, Flammable Liquids [9]). Flammable liquids are allocated to the following hazard classes according to their fire and explosion properties (EN classification see also allocation table [9]).
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F1 = Liquids with a flash point below 21°C
F2 = Liquids with a flash point of 21 to 55°C
F3 = Liquids with a flash point above 55 to 100°C
F4 = Liquids with a flash point above 100°C
F5 = Liquids, not easily inflammable
F6 = Liquids non-flammable
1.5.3 Air pollution control The maximum permitted concentrations stated in the Clean Air Ordinance (LRV [5]) must be complied with for tanks venting into the air (Chap. 7.2). Further requirements by Cantonal authorities are to be observed. For information on tank breathing losses, see Chap. 5.1. 1.6 Tank farms and transfer sites, definition 1.6.1 Tank farms Storage facilities with a usable volume above 450 l must be registered or approved (KVU [34- 01]). Installation A distinction is made between - Facilities outdoors,
· Free-standing or · Non-free-standing (buried)
- Facilities in underground concrete spaces and buildings · Free-standing or · Non-free-standing (buried)
Free-standing refers to storage tanks and pipelines the external walls of which are visible to such an extent that liquid losses can be easily detected from outside; storage tanks are also free- standing if their bottom cannot be seen from the outside but they are permanently monitored by a leak detection system for liquid losses. All other storage tanks and pipelines are considered buried. 1.6.2 Drum storage Drum storage refers to storing potentially water-polluting liquid chemicals in drums. Drums refers to vessel from 20 l up to a usable volume of 450 l. 1.6.3 Transfer sites Filling stations and drum filling systems are considered to be transfer sites. - Filling stations: Transfer between transport vessels or between transport vessels and
vessels of storage and plant facilities; - Drum filling systems: Transfer from storage or transport vessels to drums.
TRCI 2 Planning and design of tank farms Page 9 of 70
2 Planning and design of tank farms 2.1 General comments 2.1.1 Site selection and assessment of construction site Important site selection aspects for a new plant or the extension of an existing one: - Local conditions: Ground water pollution control zone including ground water pollution
control site, water pollution control area (Chap. 1.4), building zone (according to town planning), transport links (railway, road), availability of firefighting water and containment basin, utility connections (power, nitrogen for blanketing, compressed air for instrumentation and controls, steam for heating purposes, cooling media, etc.), building ground, sewer connection, exhaust air treatment, existing pollution by immission;
- Classification of liquid chemicals according to their water-polluting properties and according to their fire hazard ratings (Chap. 1.5);
- Liquid chemicals requiring, due to their hazard class, special safety measures; - Obligation to approve, register and control facilities with potentially water-polluting liquids
of Class A (KVU [34-01] and [34-01-1]), see also Chap. 6.1: Medium-sized tank farms (with tanks from 2 up to 250m3) in Water Pollution Control
Areas A ; Large tank farms (with tanks starting 250m3) in Water Pollution Control Areas A only with
exceptional approval and in Area Z only with approval; - Impact of the facility on the neighbourhood:
Possible water pollution in the event of an accident, e.g. being in the vicinity of a river, endangering potable water supplies, etc.;
Hazard to the neighbourhood through explosion or fire in case of adjoining residential areas, roads with heavy traffic, railway lines, schools, hospitals, due to the immission of aerosols or decomposition products or concurrent evaporation of stored products released in firefighting, etc.;
- Impact of the neighbourhood on the facility: Traffic accidents in the immediate vicinity involving reservoirs, neighbouring facility with increased hazard potential, air traffic, earthquake risk, flooding, climatic conditions, e.g. corrosive air from heavy traffic, chlorine or chloride plants (salines), etc.
The site selection and decisions on the size of the tanks and the farm as a whole must be made as part of a hazard analysis.
2.1.2 Planned arrangement When planning a tank farm attention must be paid to: - A clear arrangement of the individual units (rows of tanks, filling/discharging bays, piping
networks, pump groups); - Logical division of the complete facility by individual protective structures and fire sections; - Products which could react dangerously with each other or cannot be extinguished with the
same fire extinguishing equipment must be stored separately in a suitable manner; - Structural, hazard-oriented separation of tank farms from production facilities, e.g. by safety
clearances, fire walls, water curtains, tank zone with non-flammable liquids; - Escape and emergency routes (VKF Guideline 16-03d [9]) - Good accessibility for maintenance, operation and event rectification;
TRCI Edition 2009
- The accessibility of tank farms for flammable liquids must be safeguarded for mobile fire extinguishing equipment (vehicles) from at least two sides and every individual tank must be accessible by mobile fire extinguishing equipment from outside of the tank area (Fig. 1+2). Within a group of tanks, the layout of the tanks should be such that "shadow zones" (i.e. zones which the fire extinguishing equipment cannot reach or only with difficulties) do not occur in case of a fire. If this demand cannot be met due to the operational situation, fixed firefighting installations must be provided, firefighting from the top may also be taken into consideration (Fig. 3 + 4);
- The distances between tank groups have to be defined according to fire-extinguishing aspects (accessibility, possibility of inserting water walls, etc.). It is advantageous to subdivide bigger tank groups into smaller fire sections (e.g. by fireproof walls or with tanks of non-flammable liquids in between).
Fig. 1 + 2 Tank farm accessible from two sides
F
Tank Farm Guidelines for the Chemical Industry
Perimeter, drainage In case a storage tank leaks, liquid sprayed beyond the bed (spray parabola) must be collected and handled in a controlled manner. The strip to be drained must have a width of at least 0.5 times the height of the tank above the bed, measured from the tank wall. If tanks are thermally insulated or if they are equipped with protective cladding, this measure is not required.
ig. 3 Tank farm only Fig. 4 Tanks inside of the tank field (shadow accessible from one side zone) not accessible by mobile fire
extinguishing equipment or only with difficulties.
TRCI Edition 2009
0,5 x h
h
For the size of the drained area and retention volume at transfer sites see Chap. 3. The surface of the tank farm perimeter which can be wetted by leaking liquid during operation or in case of accidents is to be of a structure impermeable to liquid, weather- resistant and principally resistant against the goods stored there. These areas are to be drained in a controlled manner.
2.1.3 Tanks in underground concrete spaces General comments Storage tanks can be erected individually in underground concrete spaces; this arrangement is predominantly employed, if site conditions require the use of space under streets and yards. Structure On principle, the structure is subjected to the same requirements in relation to impermeability as normal protective structures. Selection of tanks For liquids of Hazard Classes F1 and F2 only explosion-resistant or blanketed tanks may be used. Liquids of Hazard Classes F3 and F4 and hardly or non-flammable products can be stored in tanks which are not explosion-resistant. Tanks in underground concrete spaces must be designed without a bottom outlet nozzle. Clearances The clearances between storage tanks and protective structure are to be designed in such a way that visual check of the storage tanks and the protective structures for impermeability is feasible. Where this is not possible, a leakage monitoring system is needed and the storage tanks have to be checked and cleaned inside at appropriate intervals (at least every 10 years). 2.1.4 Filling points and drum filling points Construction Filling points are preferably to be constructed as an open or semi-open structure, where necessary with a roof for protection against the elements. Easy detection of liquid losses must be guaranteed. If liquids of Hazard Classes F1 and F2 are filled, non-flammable construction materials are to be used and sufficient separation in terms of fire protection has to be arranged between the filling point, tank farm and the other facilities and buildings. Containment trays, containment beds and containment basins or their coating must be resistant to stored media and leak-proof for at least 6 months, only in exceptional cases for chemical- physical reasons, the authority issuing the permit may allow a resistance to stored media for the period required to identify the loss, repair the leak and remove the liquid.
Ventilation If a closed type of structure is to be used for special reasons, appropriate ventilation and accessibility is to be particularly considered usually requiring induced ventilation. It is to be ensured that ventilation apertures are available also immediately above ground level.
In semi-open construction, the natural air change is usually sufficient. Appropriate measures must be taken to prevent liquids and escaping vapours from accumulating in rooms at a lower level, or in sewers, pits and the like. See also VKF Guideline 28-03, Chap. 5.5 [9].
2.2 Tank and protective clearance Tank clearance Minimum tank spacing is defined as the effective clearance between tanks or between a tank and the wall. Anything reducing the effective dimension, e.g. thermal insulation must not reduce the minimum clearance. If a leak occurs in the wall of a tank, the spray parabola must be caught inside or outside of the tank bed (see Chap 2.1.2). Thermal insulation or protective cladding meets this requirement.
Protective clearance Protective clearance is measured from the outer edge of the protective structure of the tank farm to the adjoining building under the same ownership or to the building line of the neighbouring lot. The protective clearance can be reduced after consulting the authorities, if suitable measures, such as protective walls, deluge spray systems, or foam, are provided. For tank diameters larger than 10m, it must be verified for each product that the radiant heat on the building line of the neighbouring lot does not exceed 8kW/m2 in case of a fire. Calculation e.g. according to the Swiss Reinsurance Company [30]. 2.2.1 Outdoor storage tanks and drum storage Based on the "Fire Protection Guidelines, Flammable Liquids" [9], the following standard values are applicable.
Table 2.2.1: Hazard to neighbourhood (degree of hazard)
Use of building
Fire hazard low1)
Fire hazard normal 2)
Fire hazard high 3)
Min. EI 60 (nbb) and facing wall without any openings small small small
Min. not combustible small medium great
Combustible or no wall medium great great
Rating examples for type of use according to fire hazard: 1) Manufacturing, processing and storage of non-combustible materials and goods, metal processing 2) Machine manufacturing, offices, apartments 3) Processing and storage of flammable or explosive materials and goods, wood processing
Table 2.2.2: Outdoor drum storage
Clearance from drum storage to buildings (in m) Hazard to neighbourhood
(degree of hazard) Hazard Classes F1 and F2
Hazard Classes F3 to F5
Size of store (in m3) Size of store (in m3)
up to 5 up to 50 more than 50 up to 5 up to 50 more than 50
small 5* 10 15 - 5* 8
medium 10 15 20 5 8 12
great 15 20 25 8 12 15
* No protective clearance if the facing wall corresponds to EI 60 (nbb) and does not have any openings and the accessibility is safeguarded.
The protective clearance refers to drum storage if the same drums are stored for a longer period of time. Protective clearance to railway tracks, high-voltage lines and motorways should be the same as for tank farms.
Table 2.2.3: Minimum tank and protective clearance
Type of vessel Tank size Hazard class Protective clearance Tank clearance A B X
2) Y
NBG high 20m
10m
0.5 m 1) 0.5 m 1)
F1 and F2 NBG low 20m
NBG medium 25m NBG high 30m
30m
15m
500m3
40m
NBG high 20m 20m
non-explosion- resistant
0.3 D, min. 1m
Clearance A and B (VKF), X (KVU), Y (TRbF / CARBURA) see the following figure NBG: Danger to neighbourhood according to Table 2.2.1 D = Tank diameter, if there are various diameters the largest one applies. 1) = 0.8m gangway on one side per tank row 2) = The "perimeter, drainage" Chap. 2.1.2 must be met. 3) = At least the Building Dept. regulations have to be met.
TRCI Edition 2009
(Building line) (Building line)
Explanation concerning tank and protective clearance (special cases) "Fire Protection Guideline, Flammable Liquids" [9] Railway tracks A protective clearance of 15m to the main tracks is applicable according to the VKF Guideline (28-03) [9]. Further details are also contained in the VKF Guideline. High-voltage lines A protective clearance of 10m is applicable to high-voltage lines [9]. Protective clearances to high-voltage facilities of third parties are to be determined according to the directives of the Swiss Federal High-Voltage Inspectorate Article 16, [23]. If these clearances cannot be complied with, a commission of experts decides on a case-by-case basis on compensatory measures. Roads
A protective clearance of 10m is applicable to public roads (up to the roadside) [9]. For motorways, a special Swiss clearance provision in relation to tank farms does not exist. The building lines must always be taken into account. The safety spacing, which is applicable inside the works area, must be complied with as a minimum clearance. Cantonal building authorities are empowered to impose additional clearances from these building lines.
TRCI Edition 2009
2.2.2. Storage tanks in buildings Table 2.2.4: Minimum tank and protective clearance for medium-sized, cylindrical
tanks
F1
No protective clearance Building walls min. EI 90 (nbb)
Tank to wall 0.15m Tank to tank 0.25m Service gangway 0.5m Gangway on one side (escape route) 0.8m
F5 Non-explosion- resistant
and No protective
clearance F6 tanks Tank to ceiling 0.7m
The minimum tank clearances refer to the effective clearance from tank to tank or from tank to wall.
0,5 m
min 0,8 m
The clearance between tank (manhole flange) and ceiling must also be ensured. Anything reducing the effective dimension, e.g. thermal insulation, must not reduce the minimum clearance.
2.2.3 Outdoor filling points and drum filling points At transfer points for tank wagons, firm installations are to be located outside of the clearance profile for shunting tracks.
Table 2.2.5: Minimum protective clearances of filling points
Hazard class To buildings and facilities outdoors
To building line on neighbouring lot
F1 and F2
10m NBG high 15m
NBG high 8m
NBG: Danger to neighbourhood according to Table 2.2.1
The clearances are determined from the manhole or from the outlet nozzle. For explanations concerning the protective clearance and measures to reduce the clearance as well as special cases see Chap. 2.2 To the pertaining tank farm, a protective clearance is not required. Drum filling points Drum filling points for liquids of Hazard Class F1 to F4 should have, in relation to buildings and facilities, a clearance of at least 3m. For measures to reduce the clearance see Chap. 2.2.
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3 Protective structures, foundations 3.1 General comments The structural design, dimensioning and the realisation of tank farms are subject to standards and guidelines. These are, in particular:
KVU Guideline [35-1.5] and [35-1.4] SIA 261, SIA 261-1, SIA 262, SIA 262-1 [25] SN EN 206-1 [27]
The regulations and directives of the Federation, Cantons and SUVA as well as standards based on the same are to be observed. 3.2 Protective structures 3.2.1 Definitions Protective structures are constructions which make liquid losses (leakage or overfilling) easily detectable in free-standing facilities or which retain leaking liquid. - Discharge surfaces serve the secure discharge of spray losses or leakages (e.g. suitable roads
and yards); - Connecting channels and connecting pipes between discharge surfaces and basins; - Containment trays are waterproof and weather-resistant structures and serve the easy
detection of liquid losses; - Containment beds are waterproof structures principally resistant to stored goods and serve the
detection as well as retention of leaking liquid. Leaking liquid can also be retained by a separate containment basin;
- Containment basins are waterproof structures principally resistant to stored goods and serve the retention of liquids draining from trays and beds. They can also be used to burn off flammable liquids;
- Firefighting water containment basins have to be provided for tank farms with flammable liquids. A contingency plan must be available for each case, based on the water quantities of the fire-extinguishing concept.
3.2.2 Requirements of protective structures The requirements of the KVU Guideline [35-1.4] are to be met. Protective structures must thus be of concrete and placed on a ground which is capable of bearing and frost-resistant. They must resist strains during testing and operation, should not show any permanent deformation and stay waterproof. In particular, the expected chemical strain and earthquakes (see Chap 5.5) are to be taken into consideration. The protective structure is to be dimensioned in such a way that it is resistant to stored media for at least 6 months. In justified cases, the authority issuing the permit may allow a resistance to stored media for the period required to identify the loss, repair the leak and remove the liquid. For protective structures in Ex-zones, measures against static electricity are to be verified. Separate containment basins are recommended for flammable liquids. For checks and maintenance see Chap. 6.4 and 6.5. Repairs must be agreed with qualified persons and sealings should be realised according to the engineering rules.
TRCI Edition 2009
3.2.3 Discharge surfaces Discharge surfaces shall be waterproof and require a slope to the containment basin.
3.2.4 Containment trays The containment trays require a slope. Containment trays without a slope require a curb of at least 10cm. 3.2.5 Containment beds, containment basins Containment beds, containment basins for tank farms The overall area of a tank bed shall not exceed 400m2 as a rule, otherwise the beds must be subdivided into sections. To limit the water requirement for cooling and foam blanketing in tank farms with flammable liquids, the containment bed is to be divided into sections (e.g. for 2 to 9 tanks) and must have a slope of at least 1.5% so that in case of leaks or overfilling, the liquid cannot spread out under the tank but flows into a suitable containment basin or a separately arranged pump sump (see the following diagrammatic figure).
Examples: Containment bed
min. 1,5%
Protective wall Siphon/check valve; may need protection against freezing Separate containment basin quick, safe runoff of larger quantities in case of damage
pump sump
In areas where containment volumes are stipulated by law, openings for piping or similar arrangements are not permitted in walls. In exceptional cases, specially appropriate sealing techniques must be used. The dividing walls are lower than the perimeter walls, but, as a rule, are not higher than 0.5m in order to ensure accessibility. Containment basins for liquid losses and drainage for transfer sites If liquid losses have to be retained, the following arrangements may be used as containment basins: - Containment bed in the area of the transfer point; - Lower containment basin of an adjacent tank farm if functioning of the same is not impaired
and the transferred goods are not allocated to Hazard Class F1 or F2. At filling points without any roofing, precipitation must be collected and also channelled to the containment basins. The availability of sufficient containment volume is to be checked prior to every transfer. This must correspond to the maximum quantity which may escape up to the rectification of the leak, however, minimum 5m3 (see also KVU [35-1.1]). For the minimum area of the containment tray for tank wagons and tank lorries see Chap. 7.1. 3.2.6 Size of protective structures Protective structures for liquids of Class A must be able to retain at least 100% and liquids of Class B at least 50% of the usable volume of the largest vessel. Possible firefighting water and water from outdoor precipitation are to be calculated in addition. Firefighting water containment basin Containment trays and containment bed, possibly with a separate containment basin, also serve firefighting water containment. The level of the tank bed may only rise to a point where the tanks are not lifted by buoyancy forces, if they are not reliably anchored in this respect. In addition to the containment volume for the tanks, it must be possible to retain at least the firefighting water emerging from the fixed firefighting equipment during 30 minutes as well as an appropriate quantity from the use of mobile equipment (during 30 – 60 min.), if separate firefighting containment basins are not available (for details of firefighting water quantities see Chap. 4 and 5). Quantity of precipitation This quantity must correspond to that for a long weekend (3 days at 25 l/m2 = 75 l/m2). Different climatic conditions may be taken into account depending on the location. 3.2.7 Protective structures of metal - Protective structures may only be of materials which are sufficiently corrosion-resistant (see
Chap. 3.2.2); - The thickness of beds is to be determined by static calculations, if required.
3.2.8 Protective structures of mineral-based building materials Protective structures of reinforced concrete or prestressed concrete consist of a concrete construction prepared on site and, if required, of a sealing. The concrete structure must be designed in such a way that occurring deformation, particularly creep and shrinking deformation, does not have any adverse influence on the sealing. Building materials: Only high-quality concrete according to EN 206-1 [27], e.g. NPK C, may be used.
3.2.9 Linings and coatings Linings and coatings are used as sealings and corrosion protection in protective structures: - Coatings based on epoxy resin or bitumen; - Laminates (reaction resins from unsaturated polyester resin, from phenylacrylat resin or from
epoxy resin free of solvents are to be used); - Plastic plates; - Joint sealing compounds and joint tapes; - Ceramic linings; - Metallic linings. Sealings of plastic material must have a certificate for water protection capability of an accredited test body (KVU [35-1.6]), must provide the required elasticity and stick to the substrate (base). Foils of plastic material are fixed to the walls (they do not stick to the substrate).
3.2.10 Testing of protective structures The manufacturer or the erector must check and document the parts (KVU [35-1.4]). Testing comprises: - Inspection of construction: Workmanship, conformity to drawings; - Quality: Of materials and workmanship (in case of metal beds, in particular the welding
seams); - Leakage testing: Water test or another comparable test procedure (see Chap. 7.4 and 7.5). The manufacturer or the erector must issue a test protocol on these tests which records the results. The same must confirm that the part of the facility has been constructed and tested according to the engineering rules and the provisions of the TRCI. The test protocol is to be signed by the manufacturer or the erector and to be delivered to the test report administrator, the owner or the operator of the facility latest upon the acceptance of the facility; the manufacturer or the erector must keep a copy. In case of facilities requiring approval, testing is to be respectively repeated after 10 years (KVU [34-03]). 3.3 Foundations Foundations must be laid in frostproof ground with a good bearing capacity. Dimensioning of the tank supports and the pertaining foundations must be in line with the expected static load as well as with the load-bearing capacity provided for the respective region and the classification of protection requirements in respect of earthquakes (see Chap. 5.5). If the risk exists that a tank might float, the corresponding buoyancy forces must be taken into account when calculating the anchor bolts.
TRCI 4 Storage tanks and equipment Page 21 of 70
4 Storage tanks and equipment Manufacturers of facility part must check whether the same correspond to the engineering rules and must document the test results (GSchG, Art. 22 paragraph 4 [1]). See also KVU [35-1.6]. 4.1 Storage tanks 4.1.1 General comments, terms This chapter covers medium-sized tanks (usable volumes 2 to 250m3) of metal and plastic material as well as large tanks (usable volume more than 250m3) of metal. Storage tanks of reinforced concrete and prestressed concrete are not covered by the TRCI.
Terms - Standard volume: The standard volume is specified according to the R5 series of standard
numbers and is smaller or equal to the nominal volume; - Nominal volume: The nominal volume is the maximum quantity of liquid a vessel can hold on
basis of the stress calculation and its technical construction; - Usable volume: The usable volume amounts to 95% of the nominal volume for drums, small
and middle-sized tanks, 97% of the nominal volume for large tanks; - "Free-standing" storage tanks: see Chap. 1.6.1.
Requirements for storage tanks - Storage tank construction material must be resistant to the stored medium (liquids and
vapours), protected against external corrosion and able to withstand the expected thermal and mechanical stress (for metal vessels see EN 12285-1 steel tank horizontal, Annex B [27]).
- For leakage monitoring, tanks can also be constructed with a double bottom or a jacket (see Chap. 4.5.4).
- For flammable liquids, metallic (incl. coated and lined) storage tanks are to be used. - Dimensioning of tanks and their supports must take the additional forces resulting from an
earthquake into consideration (see Chap. 5.5). - Every medium-sized tank or large tank must be equipped with at least one manhole (DN 600).
Small tanks must have at least one inspection hole. Classification according to size (usable volume) - Drums 20 l to 450 l - Small tanks above 450 l to 2m3 - Medium-sized tanks above 2m3 to 250m3 - Large tanks above 250m3
Types of vessels - Drums Cans, barrels, etc. - Small tanks and
medium-sized tanks explosion-resistant or non-explosion-resistant prismatic or cylindrical Tanks with a domed or flat bottom; - Large tanks Vertical, cylindrical vessels with flat bottoms are differentiated as
follows: a) Vertical tanks where the free space above the stored medium has free access to the atmosphere; b) Vertical tanks with a fixed roof which can support a gauge pressure or
partial vacuum in the free space above the stored medium, according to operating conditions;
c) Vertical tanks with a fixed roof equipped with an internal membrane floating on the stored medium (membrane tanks);
d) Vertical tanks whose roof is constructed as a float (floating roof tanks).
Other types of vessels not listed above (e.g. spherical tanks) are possible. 4.1.2 Storage tanks of metal Corrosion
When choosing the material and wall thickness, both safety against corrosion (if corrosion is expected, additional costs should be foreseen) and the economic efficiency are to be considered. Explosion-resistant tanks A tank is considered explosion-resistant, if it can withstand an internal explosion and still does not leak. Storage tanks equipped with an inert gas blanketing system are considered to be equivalent to explosion-resistant tanks in relation to their use (hazard class). As a rule, they are used for usable volumes of up to 250m3 for free-standing storage of highly flammable liquids. - Construction according to BN 76 [36] and Annex, explosion-resistant storage tanks (according
to BN 110 [36], flat-bottom tank).The vessel does not leak, even at a maximum explosion pressure of 10bar. A major permanent deformation is acceptable. The tank is operated unpressurised, although a breathing pressure of +200mbar is permissible. Vacuum resistance according to construction drawing;
- Construction according to BN 98 [36], explosion-resistant vessels and equipment for flammable liquids and dusts. Designed for a max. explosion pressure or for an explosion pressure reduced by means of relief devices or explosion suppression (see VDI Guideline 2263, [26]). Only small localised permanent deformation may occur. Any desired operating pressure can be taken into account in the calculation;
- For horizontal tanks (installation under or above ground) explosion-resistant or non-explosion- resistant see EN 12285-1 or -2 [27];
Calculation and testing according to BN: Dimensioning and stress analysis calculation is according to BN 76 and Annex or BN 98. The position, number and nominal width of the required nozzles, manholes and supports are defined in dimensional drawings or sketches (e.g. according to BN 110). The manufacturer must initiate, at one of the listed offices (Switzerland: e.g. SVTI), the preliminary check of the calculation and construction drawing as well as the acceptance after production. Vertical tanks Free-standing vertical cylindrical tanks with a flat bottom resting on a base and a fixed roof (with or without a floating ceiling) or with a floating roof can be used for the storage of all liquids at atmospheric pressure or a slight operating gauge pressure. Calculation and testing: According to SVTI regulations P 5, [24].
Prismatic tanks The vessels must be constructed in such a way that they are resistant to the static head of liquid and to pressures and partial vacuums occurring during operation as well as external stress. If these tanks are tested with a minimum of 0.5bar gauge pressure, they are authorised for the free- standing storage of liquids with flash points of more than 55°C. Calculation and testing: According to SVTI regulations P 2, [24].
4.1.3 Storage tanks of plastics Generally used up to 100m3 usable volume for storage of potentially water polluting liquids with a flash point of more than 55°C. Calculation and testing: According to engineering rules, e.g. of the Plastics Association of Switzerland (KVS). In case of a deviation from the technical rules, evidence must be provided that the legal requirements have been fulfilled in another way.
4.1.4 Heating and cooling systems The following methods are available - Jacket around the tank or pipe wall; - Half coils or heating panels welded to the outer tank walls; - Tubular coils or heating panels inside of the tank; - Tubular coils touching the outer wall of the tank or pipe, possibly embedded in heat transfer
cement for improved heat transfer; - Electric heating system by cables or elements; - Closed refrigerant system with circulation pump and cooling machine. - Direct vapour injection into the stored medium; - Re-circulation of the stored medium through a heat exchanger; - Induction-heating systems, which transfer the electrical energy directly into the stored
medium, can be considered for heat exchangers and non-flammable liquids; - Tank sprinkling with water. Remarks - The surface temperature of the heating elements or the heating medium temperature to heat
flammable liquids must be adhered to according to TR BCI 155, Table 3.3.4-1 [36]; - A heat transfer medium which is non-flammable or flame retardant and frost-resistant and
whose boiling point is above the maximum heating temperature is to be preferred in order to avoid system pressure due to vapour tension, e.g. mixtures of water/ethylene glycol;
- Any heat transfer medium used must not cause a dangerous reaction when in contact with the stored medium;
- Electric heating systems and tracing systems for pipes have the advantage of a uniform heat transfer (W/m2), cost-effective division into individual pipe sections, virtually not heat loss and they represent an economical method of supplying heat energy;
- For hazardous zones, heating elements require an Ex test certificate.
Cooling procedures Cooling equipment as described above. The refrigerant should be non-flammable or flame retardant, and must not be too viscous at low temperatures, e.g. refrigerating brines.
4.1.5 Inert gas blanketing In order to avoid the ingress of air into storage tanks, the liquid is blanketed with inert gas (e.g. N2) (see ESCIS Volume 3, [17]). To keep the consumption of the inert gas as low as possible, a large permissible difference between the gas supply pressure and the relief pressure is used. For breathing, automatic pressure relief valves or overflow valves as well as controllers with auxiliary power can be used. They are selected according to tank stability and properties of the stored medium. The set pressure of the control valves must be aligned to the response pressure of the safety valves.
TRCI Edition 2009
If a storage tank according to BN 110 is used for non-flammable media or flammable media under inert gas blanketing, the maximum permissible operating gauge pressure amounts to +500mbar, otherwise max. +200mbar. Vacuum protection according to the permissible operating negative pressure of the tank (see details in construction drawings).
Example: For a tank according to BN 76 / BN 110:
N
2-gassing by automatic low pressure reducing valve; e.g. set point 15mbar. N2 relief by automatic overflow valve; e.g. set point 80mbar (max. permissible 200mbar).
4.1.6 Tank surface coating - Function: In addition to its main task of protecting the storage tank against corrosion, the tank
coating can also influence warming of the tank and thus breathing losses. The painting system to be used for carbon steel tanks is specified. e.g. by the following guidelines: · BN 108 according to System WBZ or SBZ; · For insulated tanks, coating with System AB or 2U according to BN 108 is recommended; · Non-insulated tanks with primer and topcoat according to BN 108, according to System
WBZ or SBZ; · Colour of the topcoat as desired; preferred shades Al-silver to white with a total heat
reflectance factor W above 70% (see table below). R Special coating materials may also be used as fire protection measures;
- Influence of the surface coating on tank warming: According to VDI Guideline 3479, [26] there is a linear relationship between the surface temperature of a hollow body and the total heat reflectance factor. The surface temperature of a body painted in black can be up to 25°C higher in central Europe than that of a similar body painted in white.
The table below, provides an overview of the total heat reflectance factor WR for the wavelength spectrum of natural sunlight (300 to 4200nm) for various coating colours.
Description of the colour
Total heat reflectance factor
WR in % (rounded off)
Black RAL 9005 3 Machine grey RAL 7031 10 Brown RAL 8011 12 Mouse grey RAL 7005 13 Green RAL 6010 14 Blue RAL 5010 19 Silver grey RAL 7001 27 Pebble grey RAL 7032 38 Red RAL 3000 43 Light grey RAL 7035 51 Ivory RAL 1014 57 Aluminium silver RAL 9006 72 Creamy white RAL 9001 72 White RAL 9010 84
Surface coatings: The total heat reflection factors given above as examples were determined for freshly completed coats of paint; they thus correspond to "good paint conditions". For an exact calculation see VDI Guideline 3479, [26].
4.1.7 Thermal insulation Thermal insulation (see e.g. BN 56 and BN 58) may be used: - In heated tanks; - For the reduction of temperature fluctuations in the gas space of tanks and thus for the
reduction of breathing losses; - As fire protection to prevent the storage medium and the construction from heating up fast
instead of tank cooling (see Chap. 5).
If thermal insulation has been provided as a fire protection measure, it has to be designed in such a way that dangerous conditions cannot arise at any filling level in the tank for 30 minutes. This requirement is fulfilled, on principle, if BN 111 is used. In this case, the following aspects are to be observed: - Insulating materials must have a Fire Hazard Index of 6 (non-flammable). Mineral fibre
sheets bound with wire netting (without any plastic components) and mineral fibre fire protection sheets (coated on one side with aluminium foil) are examples of suitable materials;
- The insulating materials must be securely fastened. If, for example, mineral fibre fire protection sheets are used with aluminium as cladding, the fire protection sheets must be secured additionally with a wire mesh;
- Tank legs or skirts must also be protected. If it is possible for fire to enter beneath the tank, then this part including the piping and valves and fittings must also be protected;
- If other materials are used instead of mineral fibres or foamed glass (e.g. sublimation coatings, sprayed cement, etc.) their suitability must be checked by an authorized institution;
- The danger of self-ignition of organic liquids which can soak into the insulation must be assessed in relation to local conditions. Mineral fibres or open-celled material must only be
used after carrying out a hazard assessment. Where necessary for safety reasons, a closed-cell material such as foamed glass must be used.
With insulated tanks it must be taken into account that if heat is generated within the tank due to an exothermic reaction, cooling from outside is not effective. 4.2 Piping 4.2.1 General comments, terms - Piping includes: Pipes, valves, fittings and connecting elements which connect storage tanks
transfer sites, pumps and production plants; - "Freestanding or buried" piping: see Chap. 1.6.1. - Hoses are connecting parts of
· Elastomeres or thermoplastics; · Parallel corrugated, braided hoses of stainless steel and the pertaining hose fittings.
4.2.2 Requirements of piping - In relation to design, manufacturing, installation, testing and safety facilities, piping (with a
permissible operating pressure ps above 0.5bar) has to fulfil the requirements of the European Pressure Equipment Directive (PED) [29];
- The piping materials and valves and fittings must be resistant to the medium being transferred (liquids and vapours) and protected against external corrosion as well as the expected thermal and mechanical loads. For leak monitoring, piping can also be equipped with a jacket (see Chap. 4.5.4). For piping of steel, copper and plastics, see also KVU [35-1.2] Chap. 3.4;
- For flammable liquids, metallic (incl. coated or lined) piping must be used. Connecting parts of elastomeres, e.g. hoses, require a hazard analysis;
- Depending on the medium, measures in relation to electrostatics have to be taken (see Chap. 5.2.5);
- Piping must be designed for at least PN 10. Exception: Pipes of plastic materials minimum PN 4, however, connecting parts must also be PN 10;
- On principle, any liquid loss from piping must be easily detected. In case of buried piping, liquid losses must be retained;
- Piping and its support must withstand earthquake loads (Chap. 5.5); - To reduce the possibility of leakage, all system parts shall be welded wherever possible.
Excluded are parts which need to be removed such as control valves, safety valves and fittings, etc. For further information see DIN 4754, [28].
4.2.3 Design, installation - Whenever possible and expedient, pipelines must be installed above ground, and be visible
and accessible. They should, however, be largely protected against possible damage; - Determination of distances for piping supports; - Avoidance of impermissible pressure surges (e.g. in closed pipes, pressure blows) see also
DGV [29]; - The number of joints between individual pipe sections and valves and fittings that can be
disassembled must be kept to a minimum, and must be easily and safely accessible. For increased protection against leakage, special measures (e.g. tongue and groove and flanges or special gaskets) are to be provided;
- For pipe leak monitoring purposes and leakage containment, e.g. double-walled pipes can be used;
- In case of dangerous liquids a check has to be conducted as to whether detachable joints at exposed locations need any special spray guards for personal protection.
4.2.4 Connection of pipes to tanks and tankers - Any re-siphoning of liquid from the tank via an immersion pipe must be prevented by
technicalmeans (e.g. vent holes);
- If pipe connections are required under the level of the liquid, special tank valves and fittings must be used (see Chap. 4.3.2);
- If hoses are used as a connection between mobile tanks or tankers and fixed piping see next chapter;
- Instead of hoses, articulated pipes can be used as floor arms or wall or gallery arms for connections at the bottom or top of a mobile tank or tanker. These have to be selected according to medium requirements and are to be identified and tested by an authorised inspector;
- Measures against electrostatic hazards (see Chap. 5.2.5).
4.2.5 Hoses Hoses are particularly used in tank farms to - connect mobile and fixed parts of facilities; - load and discharge tankers, tank wagons or containers.
Hoses should only be used as a permanent alternative to fixed pipes, if the advantages offered by their use cannot be abstained from (they should not be just a "convenient substitute" for a fixed pipe). A hazard analysis must be carried out. It may be that additional safety measures are needed. If hoses are used, the instructions of ESCIS, [17] and the "BG Chemical Bulletin" [31] are to be taken into consideration. The safe use demands that - The hose quality is carefully selected for the respective conditions of use; - The hoses correspond to relevant standards and the state of the art and that they have been
tested; - There is an unambiguous identification of the hoses (see DIN 2823 a. 2827 [28]); - The hoses are appropriately stored; - The hoses are manufactured, assembled and installed by skilled persons; - The hoses are used as intended (regular training of operators); - Regular tests are conducted; - Depending on the medium, measures in relation to electrostatics are taken (see Chap. 5.2.5). 4.2.6 Gas balance, pressure compensation lines - It must not be possible to isolate vent lines (pressure compensation lines). If outlets lead into
the atmosphere, they must be protected against the ingress of rainwater and dirt and must be positioned in such a way that escaping vapours can dissipate without representing a hazard. The minimum nominal pipe diameter amounts to DN 40 (Exception: Ventilation by pressurised inert gas);
- Facilities in the vicinity, e.g. ventilations, stacks, sewer systems, lights and lift shafts, are to be taken into consideration;
- The dimensions of pressure compensation lines must be sized in such a way that dangerous gauge or negative pressure cannot result when tanks are rapidly filled or discharged or rapid temperature fluctuations occur. The pressure losses of vent systems and flame arrestors must be taken into account;
- To determine the max. breathing volume flow, the formulae according to TRbF [15] may be used;
- In gas balance and pressure compensation lines, possible condensate formation must be taken into account;
- The installed pipes usually need a slope towards the tank, otherwise a drainage device must be installed on the lowest point;
- Several tanks may be vented by a common pipe, provided the different media do not enter into any dangerous mixtures, condensation or solids formation with each other.
4.2.7 Overspill, overflow equipment The arrangement must ensure that leaking liquid flows into the protective structure in case of overspilling (see KVU [35-1.3]). 4.2.8 Distributing and return lines If a filling line serves several tanks, it must be ensured that overspilling of these tanks is prevented (see Chap. 4.5.3). If facilities use return lines, it must be ensured that the return liquid flows into the vessel from which it was taken. Incorrect connections must be excluded (see KVU [35-1.2]).
4.2.9 Testing of piping Piping must be tested by the erector in accordance with applicable regulations (e.g. DGV or TR BCI 151). Testing comprises: Non-destructive testing (e.g. visual, radiation and/or penetrating tests), pressure testing and leakage testing. Leak detection pipes are to be tested according to KVU [35-1.2]. A protocol is to be prepared for conducted tests.
4.2.10 Pipe insulation Pipe insulation may be designed, e.g., according to BN 55 and BN 56.
4.3 Valves and fittings 4.3.1 General comments - Valves and fittings must be able to withstand the same loads as piping; - They are to be arranged in an accessible manner and easy to operate; - The measures to safeguard impermeability in relation to the atmosphere must correspond to
the hazards associated with the medium, e.g. bellow seal valves or diaphragm valves with backup stuffing boxes.
4.3.2 Shutoff valves Shutoff valves at the tank which are subject to the static head of the tank contents must fulfil the following requirements: - They must be installed directly on the tank; - They must be resistant to frost (i.e. they cannot be destroyed by the effects of frost, and frost
does not make them less effective); - In case of disk valves, the static head of the tank contents must support the closing effect; - When the valve is closed, the stem stuffing box must not be subject to the static head of the
liquid in the tank. Piping components, flange connections and shutoff valves which are subject to the static head of the tank contents must be able to withstand a fire in the tank basin and stay tight. It is therefore recommended, e.g. in tanks with bottom outlets, to install a shutoff valve directly on the tank which closes itself without external energy in case of a fire. In case of pneumatically operated valves, flammable control air connections are thus to be used. In addition, the shutoff valve should be either fireproof or protected by insulation or cooled by a deluge spray system.
4.3.3 Vent valves If the gas space in a tank is separated from the atmosphere or from a connected exhaust air system a vent valve is needed. - Mechanical (dead weight or spring-loaded) control valves or seal pots can be used as vent
valves. The response pressure is to be selected in such a way that the pressure change (depending on the type of valve 10 – 100% of the response pressure), which is reached at the max. volumetric flow rate, causes the design gauge and negative pressure to be adhered to. In the determination of the volumetric flow rate, that of breathing (Chap. 5.1.2) as well as that of the filling or discharging pump (ISO 28300 [[20]]) is to be taken into consideration;
- Commercially available breather valves involve high maintenance costs to ensure the reliable impermeability of the valve seats. For small pressure differences, seal pots offer higher operating reliability; for larger pressure differences pressure/vacuum relief valves with actuators controlled by external energy should be installed. It must be ensured that if the external energy supply fails, backup relief devices still provide protection;
- If the vent devices are not adequate to cope with a major mishap (failure of the blanketing gas valves), additional relief valves or bursting disks can be installed;
- Fire emergencies must be covered by other safety measures.
4.3.4 Flame arresters Flame arresters are devices which are installed at the opening of a part of equipment or in the connecting pipe of a facility system; their intended function is to facilitate flow but prevent a flame front from entering the system.
Explosion in piping: The pipe deflagration is an accelerated explosion in a pipe. Having passed through an instable transient region, it becomes a stable detonation. In this detonation region, which is stable again, temporary pressures of more than 80bar can occur. In addition to the "dry" devices subsequently described, "wet" devices (liquid seal chambers), fast-acting valves, devices for suppressing explosions or other specific solutions may be used for certain applications. Types of dry devices Dry flame arresters: Are based on the principle of dividing the flow cross section, e.g., into narrow passages in which flame propagation is no longer possible. Only those devices may be used, which - according to 94/9/EC ("ATEX 95“) [[32]] and EN 12874 [[27]] - are approved by an inspection authority for the intended purpose of use (explosion group, operating temperature/pressure, etc.). Flame arresters are classified according to the combustion process (endurance burning, deflagration, detonation as well as their variants) and according to the type of installation (explosion end, volume or pipe arrester). Endurance-burning-proof devices: Prevent the propagation of a flame front in case of prolonged burning of a combustible-air mixture and/or in case of an atmospheric explosion. The device must withstand the occurring temperature and pressure load. In case of endurance burning, the flame must be able to burn off freely. Deflagration-proof devices: Are devices which prevent the propagation of a flame front in case of an explosion (observe the max. permissible L/D ratio) and withstand the occurring thermal and mechanical load. Mostly, they are not endurance-burning-proof. Depending on the individual application and the purpose of protection deflagration end, deflagration volume and deflagration pipe arresters are installed. Detonation-proof devices: Prevent the propagation of a flame front in case of an explosion and in case of a detonation and withstand the occurring pressure load. Detonation-proof flame arresters, however, are not in themselves resistant to endurance burning. Application guidelines Substances involved: - Flammable liquids with a flash point below 55°C; - Liquids with a flash point above 55°C, if the flash point is not at least 5°C above the liquid
temperature. Protected installations: - Vent outlets and other openings, such as level gauge tubes which are open to the atmosphere
or which are led into other gas-filled spaces; - Gas balance lines; - Liquid lines which can run empty in the course of operation and which are not separated by a
self-closing shutoff valve from the atmosphere or other facility parts.
Installations not requiring protection: - Openings which as a rule are closed, e.g. manholes, dipstick, sampling and cleaning openings; - Inlet and outlet lines which are continually filled with liquid during operation; - Vent nozzles directly open to the atmosphere on explosion-resistant tanks; - Blanketed tanks - Discharge lines after safety relief valves. Installation guidelines - Vent nozzles and short vent lines (L/D less than 20) must terminate at their free end with an
endurance-burning-proof flame arrester; - Longer vent and gas pressure balance lines must be provided with detonation-proof flame
arresters and located immediately next to the tank or equipment which is to be protected; - If the vent lines from several tanks are brought together in a common header, as a rule, a
separate detonation-proof device must be installed immediately in front of each tank; - Larger facilities must be divided into emergency compartments to prevent a fire, explosion or
detonation from spreading; - The pressure drop in flame arresting devices and the associated piping must not go beyond the
permitted gauge pressure/vacuum of the tank at the maximum occurring volumetric flow rate; - Flame arresters must be protected against the ingress of foreign matter. Restrictions in the use of dry devices Flame arresters for media which tend to - foul - polymerise - corrode - solidify - freezing in tight gaps are to be replaced by other safety devices (see above). Appropriate heating of the device (not possible for all devices) can prevent the danger of freezing or solidifying in many cases.
Safety, maintenance and checks (SIWAKO) To ensure adequate protection by flame arrestors, these must be periodically subjected to a visual check. The intervals and the type of cleaning used (mechanical and/or chemical) depend on the instructions of the manufacturer and the conditions at the site involved.
4.4 Pumps Pump types are to be selected according to tasks (e.g. filling or discharging of tanks), the medium (e.g. flammable solvents or acids, liquids with high viscosity) and the installation location (e.g. on top of or next to the tank). For critical liquids sealless pumps or pumps with double mechanical seals are required. Simple mechanical seals or even stuffing boxes can be sufficient for less critical pumps. For different pump types different monitoring systems are recommended or even required. For canned motor pumps, storage monitoring (temperature, bearing vibration) is stipulated for flammable liquids. For magnetic clutch pumps, monitoring of the shroud is recommended, depending on the medium. Pumps may only be in operation as long as this is required for the conveyance of liquids. Pumps must be automatically stopped if filling or dry-running safety devices are activated.
Flowrate when filling storage tanks (according to KVU [35-1.1]): The Flowrate in small tanks must not exceed 200 l/min (12m3/h), in medium-sized tanks 800 l/min (48m3/h). In gravity discharge, 1’800 l/min (108m3/h) may not be exceeded. Dry-running interlocks for pumps Dry-running interlocks must be installed in tanks containing flammable liquids without inert gas blanketing in order to prevent that an ignitable gas mixture enters the pump (tank running dry). They also avoid dry-running and resulting pump damage. Different types are available: - Level switch (LS); - Flow switch (FS); - Instruments for current/power monitoring. For Ex-protection, the ATEX Guideline [32] is to be taken into consideration (see also Chap. 5.2.). 4.5 Instrumentation and control systems 4.5.1 General comments, terms General comments Instruments and equipment must be defined in accordance with expected loads and environmental impacts and protected, if required. In particular control devices and sensors of overspill protection systems, leak detection devices as well as automatic level instruments must have a certificate for water protection capability of an accredited inspection authority (KVU [35-1.6]).
Terms - Overspill protection: Systems which prevent storage tanks and mobile container from being
overfilled; - Special overspill protection: Storage tanks in the chemical and pharmaceutical industry
usually use special overspill protection systems. These comprise sensor, control device, shutoff valve and alarms. For special requirements see CSME [19].
- Leak detection systems: Enable the identification of liquid losses from tanks and piping. 4.5.2 Level instruments (level measurement) Storage tanks must be equipped with level instruments. Level instruments are devices which indicate the level in % or the liquid quantity according to volume or weight. On principle, level instruments must be used without a connection (nozzle) below the level of the liquid (KVU [35- 1.3]).
4.5.3 Overfill protection Overfill protection systems must ensure that the maximum permissible level in a tank or transport vessel is not exceeded using by cutting of the liquid supply automatically and triggering an alarm. This measurement system should be independent of the level measurement system and should preferably use a different measuring principle. This requirement is also applicable if tanks are connected by a common filling line. The overfill protection must be allocated to the tank which is to be filled (see KVU [35-1.2]). Storage tanks in the chemical and pharmaceutical industry usually use special overfill protection systems (see above).
The maximum permissible level corresponds to the usable volume (see Chap. 5.1.1) for liquids stored at room temperature. Fill and special overfill protection systems must correspond to engineering rules.
4.5.4 Leak detection systems If liquid losses cannot be easily identified visually, a leak detection system must be installed. The same enables the detection of liquid losses from tanks and piping. - Leak detection systems for vertical tanks with double bottoms:
The negative pressure between the two bottoms must be monitored and recorded at least once a month for control purposes;
- Leak detection systems for double-walled vessels and piping: The gauge or negative pressure in relation to the atmosphere between the two walls of the component must be monitored. If this monitored pressure deviates from a predetermined set value, an alarm must be triggered;
- Leak detection systems with liquid sensors: Liquid sensors detect any losses at the lowest point in the space between the walls of the component or at the lowest point in the protective structure (pump sump) and trigger an alarm;
- Leak detection systems with gas detectors: Gas detectors identify gases and vapours escaping from leaks in piping and vessels and trigger an alarm;
- Leak detection systems for vertical tanks with double bottoms: Buried double-walled vessels and piping require a test certificate.
4.5.5 Temperature switch / electric circuit breaker Electric heating systems require a fault current circuit breaker (FI switch) for TN systems or an isolation-monitoring instrument for IT systems. Redundant temperature safety switches are required for the temperature protection of resistance heating cables.
TRCI 5 Ecology, safety and fire protection Page 34 of 70
5 Ecology, safety and fire protection 5.1 Displacement and breathing losses The emission losses of a facility must range within the permissible LRV limits (see Chap. 7.2).
5.1.1 Displacement losses Displacement losses arise during tank filling. For tanks vented to the atmosphere, the volumetric rate of discharge is usually provided in a sufficiently accurate manner by the pump discharge rate. Possible measures for reducing these losses are: - Pressure balance line - Other measures for breathing losses Apart from breathing (see below) also the volume flow of a discharging pump has to be taken into consideration in tank venting.
5.1.2 Breathing losses Breathing losses occur due to changes in atmospheric pressure and temperature. The most important parameters influencing breathing losses are: - Saturation of the space above the liquid with vapour. This is principally determined by the
temperature in the gas space and the liquid together with the frequency and the extent of the transfer;
- The physical properties of the liquid, such as vapour pressure and latent evaporation heat as a function of temperature;
- The meteorological conditions at the storage location, such as outside temperature, direct and diffuse radiant heat, the effects of wind, strong precipitation (e.g. thunder storms), etc.;
- The condition of the tank surface, e.g. thermal insulation, colour, etc.
The volume of gas breathed due to a temperature increase in the gas space is to be determined by means of the gas equations. In case of highly volatile liquids, the change in the gas constant due to widely varying vapour contents at the temperature prior to the increase as compared to the temperature after the increase must be taken into account. The breathing loss is calculated using the breathing volume and the degree of saturated vapour. For storage tanks with rare transfers, 100% vapour saturation is assumed. For storage tanks with daily transfers, a relative vapour saturation of approx. 57% in winter and 63% in summer may be assumed, e.g., for substances similar to petrol (VDI Guideline 3479, [26] and ISO 28300 [20]). Apart from the flowrate of a discharging pump, also the flowrate due to a temperature decline is to be taken into consideration for purposes of tank safety (negative pressure). Rapid cooling, e.g. by strong rains, is to be included (see ISO 28300 [20] in this respect).
Temperatures in storage tanks: Annual measurements of the gas temperatures above the stored liquid in an uninsulated, flat- bottom and half-filled tank of 100m3 SS resulted in the following values at an outdoor site near Basle in 1989: - Annual extreme values (absolute max. or min. temperature): tmax = 45°C, tmin = 0°C - Monthly fluctuation (difference highest/lowest temperature): t = 30°C - Daily fluctuation (difference highest/lowest temperature): t = 25 °C - The max. temperature rise due to the weather amounted to approx. 5°C/h. On exposed sites (e.g. in the Canton of Valais) the span between the extreme values throughout the year and the monthly and annual fluctuations must be increased by 5° to 10°C. The daily temperature fluctuations of the stored liquid are very small, depending on the filling
level. Measurements have shown that the temperatures agree with the respective daily average temperatures.
5.1.3 Measures to prevent or reduce emissions Two-pressure control systems: Tank breathing can be regulated by a two-pressure control system. At a set gauge or negative pressure, air (or nitrogen) and vapour is discharged or air (or nitrogen) admitted. For some stored liquids, the daily gas space pressure fluctuations can be compensated with this set pressure difference without any gas losses. Thermal insulation: Thermal insulation on a free-standing tank or locating a tank in the earth reduces the daily temperature fluctuations in the gas space to a few centigrades. The long-term temperature fluctuations take place so slowly that discharging into the atmosphere frequently ranges within LRV tolerance values. Thermal insulation, if designed according to BN 111, also provides advantages in relation to fire protection. Tank sprinkling: This method is used to reduce the daily temperature fluctuations in the gas space above the stored liquid. This method is suitable to avoid temperature extremes. As a rule, however, permanent sprinkling cannot be considered because of the water consumption. Cold traps: The gases leaving the tank are cooled, the evaporating liquid condenses with the exception of a small residual amount and the condensate can be returned to the tank. Blanketing liquid of low vapour pressure: Represents an ideal method to prevent the space over the liquid from becoming saturated with vapour, however, only rarely is there a suitable blanketing liquid for the liquids normally stored. The measure may be used, e.g. in effluent storage. Roofing: This protects the tanks from direct sun radiation and results in lower daily fluctuations in the temperature of the gas space. As a rule, this method alone is not sufficient to keep the breathing losses within the LRV tolerance values. In addition, roofing is very undesirable if an automatic deluge spray system is not available in case of a fire. Exhaust air treatment: This concerns the treatment of the gas volumes discharged from tanks in facilities established for this purpose, e.g. incinerators, biofilters, adsorption with subsequent desorption and product recycling, etc. Floating roof or floating membrane: The liquid surface is covered by the tank roof floating on it or, in the case of fixed roof tanks, by a floating membrane. When the liquid level falls, however, all of the liquid still wetting the tank wall is lost to the atmosphere. Reflecting coats of paint: See Chap. 4.1.6.
5.2 Liquid losses Potentially water-polluting liquids are allocated to 2 classes (Chap. 1.5.1). Different water pollution control measures are required according to the water pollution control zone (Chap. 1.4). In order to avoid or retain liquid losses, organisational measures are also to be taken into consideration apart from structural and equipment measures. For details see - Chap. 2.1.2, Planned arrangement (drainage in tank surroundings); - Chap. 3, Protective structures, foundations; - Chap. 4.2, Piping (requirements, design, …) - Chap. 4.5, Instrumentation and control systems (against overfilling or leak detection
systems); - Chap. 6.4, Operation and maintenance 5.3 Plant safety 5.3.1 Ex-zone classification If flammable liquids are stored or transferred, the areas concerned are to be classified and identified according to Ex-zones as well as explosion groups and temperature classes corresponding to the stored goods. The classification can be performed on basis of SUVA Bulletin 2153, [16] and TR BCI 155 [36]. Only equipment parts may be used which conform to the respective zone, explosion group and temperature class.
5.3.2 Measures against hazardous effects of electric currents The following measures are required for tank farms located in areas influenced by other external electrical facilities and industrial lines (EMC see TR BCI 119, [36]): - The tanks must be protected against corrosion due to stray currents; - It is thus required to have all electrically conducting components meshed as thoroughly as
possible; - Stray currents from rail and industrial installations must not cause any undesirable effects,
such as spark formation or potential differences; - The type of protection of the electrical installations must be commensurate with the product
and local conditions and must be specified by the authorities and the operator. The highest hazard class to be expected in the future must be used (see Chap. 1.5.2);
- Underground piping, which is not electrically insulated, must be protected against external influences. Special attention must be paid to the effects of metal DC cables laid in the earth and on foundations;
- Rules to judge the explosion hazard in facilities with hazardous areas as well as the zone classification are contained in SUVA Bulletin 2153, [16];
- For proper EMC (electromagnetic compatibility) installations see TR BCI 119. Devices and protective systems as well as auxiliary equipment used in hazardous areas must conform to the ATEX Guideline [32] and the VGSEB [33].
5.3.3 Lightning protection systems The SEV 4022 [23] lightning protection provisions must be met (see also SN EN 62305-1 to 4 [27]). For outdoor installations storing flammable liquids, different measures are to be taken in accordance with their flash point (under or above 55°C). All devices with electric cables leading into the tank interior must be equipped with a lightning protection system. It is not required to protect the other instruments (see SEV 3425 [23]). Lightning protection system - External lightning protection system (arrester line); - Internal lightning protection system (potential equalisation), see sketch in Chap. 7.6. For EMC and lightning protection/earthing see also TR BCI 119 [36]
5.3.4 Protection against electrostatic charging For flammable liquids the hazard of electrostatic charge has to be considered (e.g. correct earthing, use of conductive hoses, no insulating coating). Measures to be taken are included in TI BCI 8 [36]. This is applicable to - Flammable liquids with a flash point below 55°C; - Liquids with a flash point above 55°C, if the flash point is not at least
5°C above the liquid temperature. - Mixed liquids with a flash point above 55°C, if the flash point is not at least 15°C above the
liquid temperature.
5.3.5 Safety measures in case of an energy failure In case of an energy failure (electric power, control air, nitrogen, vapour, water, etc.) the measures are to be defined in accordance with the risk analysis and all transfer operations must possibly be interrupted. I.e. valves assume the predetermined safety setting, transfer pumps are automatically switched off. Restarting is to be governed by operating instructions.
5.3.6 General safety measures Special product properties For products, which can have a dangerous pressure or temperature increase because of a quick reaction, e.g. polymerisation, special safety measures must be specified. Inspection The operator shall inspect tank farms regularly to monitor their safe operation and to eliminate any defects. This is in addition to the maintenance and inspection work according to Chap. 6.4 and 6.5. Railings, stairways, platforms Railings, platforms, stairways and ladders are to be constructed in accordance with Ordinance 4 concerning the Labour Act [18] and the EKAS and SUVA Guidelines and "Merkblätter". Roads The roads next to vehicles are to be kept free during the whole period of transfer so that the unobstructed departure and access of emergency vehicles is possible at any time. The vehicles have to be protected against rolling and collisions with other vehicles by constructional and/or organisational measures.
TRCI 5 Ecology, safety and fire protect

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TRCI - Bundesamt für Umweltschutz