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Document type: International StandardDocument subtype:Document stage: (30) CommitteeDocument language: E

Date: 2011-01-28

ISO/CD 80079-38

ISO/TC 31/SC 31M

Secretariat: DIS

Explosive Atmospheres — Part 38: Equipment and components in explosiveatmospheres in underground mines

Atmospheres explosibles — Partie 38: Appareils et composants dans les mines souterraines grisouteuses

Warning

This document is not an ISO International Standard. It is distributed for review and comment. It is subject tochange without notice and may not be referred to as an International Standard.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights ofwhich they are aware and to provide supporting documentation .

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Copyright notice

This ISO document is a working draft or committee draft and is copyright-protected by ISO. While thereproduction of working drafts or committee drafts in any form for use by participants in the ISO standardsdevelopment process is permitted without prior permission from ISO, neither this document nor any extractfrom it may be reproduced, stored or transmitted in any form for any other purpose without prior writtenpermission from ISO.

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Reproduction for sales purposes may be subject to royalty payments or a licensing agreement.

Violators may be prosecuted.

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Contents Page

Foreword ......................................................................................................................................................vi

Introduction ................................................................................................................................................. vii

1 Scope ................................................................................................................................................1

2 Normative references .......................................................................................................................1

3 Terms, definitions and abbreviated terms.......................................................................................3

4 Requirements for equipment (machines) and components ...........................................................9 4.1 General..............................................................................................................................................9 4.2 Ignition hazard assessment ........................................................................................................... 10

4.2.1 Formal analysis .............................................................................................................................. 10 4.2.2 Assessment with faults .................................................................................................................. 11

4.2.3 Establishing the maximum surface temperature .......................................................................... 11 4.2.4 Dust deposits and other material in the gap of moving parts ...................................................... 11 4.2.5 Ignition hazard assessment report ................................................................................................ 11 4.2.6 Ignition sources .............................................................................................................................. 12 4.3 Non-electrical equipment and components .................................................................................. 12 4.4 Electrical equipment and components .......................................................................................... 13

4.4.1 General............................................................................................................................................ 13 4.4.2 Electrical equipment protection..................................................................................................... 13 4.4.3 Overcurrent protection................................................................................................................... 13

4.4.4 Earth-fault protection ..................................................................................................................... 14 4.4.5 Mechanical protection of live parts ............................................................................................... 15

4.4.6 Electric cables that are part of the equipment .............................................................................. 15

5 Additional requirements for specific equipment and components .............................................. 16 5.1 Cutting and stripping equipment ................................................................................................... 16 5.1.1 General............................................................................................................................................ 16 5.1.2 Machines with cutting picks .......................................................................................................... 16 5.1.3 Stripping machines ........................................................................................................................ 17 5.2 Rope haulages for level and inclined transport ............................................................................ 17

5.3 Fans ................................................................................................................................................ 17 5.3.1 Ventilating fans for use underground............................................................................................ 17 5.3.2 Other fans ....................................................................................................................................... 19

5.4 Diesel engines ................................................................................................................................ 20 5.4.1 General requirements..................................................................................................................... 20

5.4.2 Flames and hot gases .................................................................................................................... 21

5.4.3 Mechanically generated sparks ..................................................................................................... 21

5.4.4 Electrical apparatus and systems ................................................................................................. 22 5.4.5 Static electricity .............................................................................................................................. 22 5.4.6 Electrical protection ....................................................................................................................... 22

5.5 Air compressors ............................................................................................................................. 23 5.6 Drilling equipment and components ............................................................................................. 23 5.7 Brakes ............................................................................................................................................. 23 5.7.1 Brakes used only for stopping in emergency ............................................................................... 23 5.7.2 Service brakes (including friction brakes and fluid based retarders) .......................................... 23 5.7.3 Parking brakes................................................................................................................................ 24 5.8 Traction batteries, starter batteries and vehicle lighting batteries .............................................. 24 5.9 Optical fibres used on machines and electromagnetic radiation from components on

machines ........................................................................................................................................ 24

5.9.1 External pipes/optical fibres .......................................................................................................... 24

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5.9.2 Radio-frequency radiation from equipment .................................................................................. 25 5.10 Gas monitoring systems ................................................................................................................ 25

6 Fire protection ................................................................................................................................ 25 6.1 General ........................................................................................................................................... 25 6.2 Non-metallic materials ................................................................................................................... 26 6.3 Hydraulic and pneumatic equipment ............................................................................................ 26

6.4 Requirements for cable-reeled equipment .................................................................................... 27 6.4.1 General ........................................................................................................................................... 27

6.4.2 Special requirements ..................................................................................................................... 28 6.5 Fire prevention on electric cables that are part of the machine................................................... 28 6.6 Conveyor belting ............................................................................................................................ 28

7 Information for use......................................................................................................................... 29 7.1 Signals and warning notices ......................................................................................................... 29 7.2 User instructions ............................................................................................................................ 29 7.2.1 Information on use ......................................................................................................................... 29 7.2.2 Information on maintenance and repair ........................................................................................ 29

7.3 Marking ........................................................................................................................................... 29

Annex A (informative) Example of an ignition hazard assessment for a conveyor belt intended foruse in a coal mine .......................................................................................................................... 31

A.1 General ........................................................................................................................................... 31 A.2 Category and intended use of the equipment ............................................................................... 31 A.3 Construction/description of the equipment .................................................................................. 31 A.4 Assessment .................................................................................................................................... 32

Annex B (informative) Example of an ignition hazard assessment for a shearer loader intendedfor use in a potentially explosive atmosphere of a coal mine ...................................................... 36

B.1 General ........................................................................................................................................... 36 B.2 Category and intended use of equipment ..................................................................................... 36

B.3 Construction/description of the equipment with regard to ignition protection........................... 36 B.4 Ignition control and monitoring system ........................................................................................ 37

B.5 Compliance with the basic methodology and requirements in ISO/CD 80079-36 ....................... 37 B.6 Ignition hazard assessment of the electrical parts of the equipment .......................................... 38

B.7 Ignition hazard assessment of non-electrical ignition sources ................................................... 38 B.8 Equipment marking ........................................................................................................................ 38

Annex C (normative) Ignition sources ....................................................................................................... 45 C.1 Hot surfaces ................................................................................................................................... 45 C.2 Flames and hot gases (including hot particles)............................................................................ 45 C.3 Mechanically generated sparks ..................................................................................................... 46 C.4 Electrical apparatus ....................................................................................................................... 46 C.5 Stray electric currents.................................................................................................................... 46

C.6 Static electricity.............................................................................................................................. 47 C.7 Lightning ........................................................................................................................................ 47

C.8 Radio frequency (RF) electromagnetic waves from 10

4

Hz to 3 × 10

12

Hz (high frequency) ....... 47

C.9 Electromagnetic waves from 3 × 1011

Hz to 3 × 1015

Hz ................................................................ 48

C.10 Ionizing radiation ........................................................................................................................... 48 C.11 Ultrasonics ..................................................................................................................................... 48 C.12 Adiabatic compression and shock waves .................................................................................... 48 C.13 Exothermic reactions, including self-ignition of dusts ................................................................ 49

Annex D (informative) Guidance on potential risks for variable speed drives (VSD)............................... 50

Bibliography ............................................................................................................................................... 51

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Page

Figures

Figure 1 — Assessment table for Group I equipment .................................................................................... 11

Figure B.1 — Layout and construction of the coal face shearer loader .......................................................... 37

Tables

Table 1 — Combination of materials............................................................................................................. 19

Table 2 — Limit values for hydraulic fluids.................................................................................................... 27

Table A.1 — Example of an ignition hazard assessment for a mining conveyor, Group I, EPL Mb................. 32

Table B.1 — Example of an ignition assessment for a shearer loader, Group I, EPL Mb ............................... 39

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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has beenestablished has the right to be represented on that committee. International organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with theInternational Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 80079-38 was prepared by Technical Committee ISO/TC 31, Equipment for explosive atmospheres,Subcommittee SC 31M, Non-electrical equipment and protective systems for explosive atmospheres.

ISO 80079 and ISO/IEC 80079 consist of the following parts:

ISO/IEC 80079-20-1: Explosive Atmospheres - Part 20-1: Material characteristics for gas and vapourclassification — Test methods and data

ISO/IEC 80079-20-2: Explosive Atmospheres - Part 20-2: Material characteristics — Combustible duststest methods

ISO/IEC 80079-34: Explosive Atmospheres - Part 34: Application of quality systems

ISO 80079-36: Explosive Atmospheres - Part 36: Non-electrical equipment for explosive atmospheres —Basic method and requirements

ISO 80079-37: Explosive Atmospheres - Part 37: Non-electrical equipment for explosive atmospheres —Non electrical type of protection constructional safety 'c', control of ignition source 'b', liquid immersion 'k'

ISO/IE 80079-38: Explosive Atmospheres - Part 38: Equipment and components in explosive

atmospheres in underground mines

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Introduction

This International Standard specifies requirements for the constructional features of equipment andcomponents that may be an individual item or form an assembly, to enable them to be used in mines, or partsof mines, susceptible to explosive atmospheres of firedamp and/or combustible coal dust.

Most of the electrical equipment used on mining machinery is certified as an individual item of equipment e.g.the motor, switchgear etc., and meets its own marking requirements. This Certification, however, does not dealwith the interconnection of these items of equipment by cables or the machine electrical power system as anentity. The equipment and components including their interconnections should be assessed, from an ignitionpoint of view, by the manufacturer.

Both non-electrical equipment and the interconnection of electrical/non-electrical equipment require an ignition

hazard risk assessment.

Therefore, it is necessary that not just the equipment, but all its parts, is examined by the manufactureraccording to a formally documented hazard assessment that establishes and lists all the possible ignitionsources of the equipment including the cables and electrical supply system. The documentation shall list themeasures that shall be introduced to prevent possible ignition sources becoming effective.

The need for this International Standard arises because of major operational differences between undergroundmining operations and those in other industries working with, or in, potentially explosive atmospheres.Examples of these differences are:

the product being won from the underground strata may be combustible and continually releasesfiredamp during the winning process;

the ignitability of the atmosphere around equipment and components usually depends upon the amountof dilution offered by an active ventilating system;

the atmosphere in the general body of mine air in which machinery is working may change from one thatis potentially explosive to one that is explosive (for example, during an outburst of firedamp);

persons working in the mine are usually situated within the potentially explosive atmosphere;

there is a need to monitor constantly the mine atmosphere at strategic places to ensure that power canbe disconnected from all equipment except that which is suitable for use in an explosive atmosphere;

in gassy coal mines, an explosion of firedamp at a machine can raise a combustible dust cloud thatexacerbates the explosion;

some mining machinery, especially that associated with winning the product, contains cutting devices anddrilling devices that are intended to cut into the combustible product as part of their normal operation. Thisintroduces an ignition risk from frictional heating or frictional sparking from contact with strata containinghigh concentrations of quartz or iron pyrites;

long roadways in coal mines are equipped with mineral conveying systems carrying a product that has apotential for raising an explosive dust cloud.

To decide which equipment or its component parts should merit inclusion in this International Standard, ignitiondata has been examined based on French, German and UK experience.

When drafting this International Standard, it has been assumed that equipment and components are:

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designed in accordance with good engineering practice, taking account of expected shocks, vibrationsand failure modes;

of sound mechanical and electrical construction;

made of materials with adequate strength and of suitable quality;

free from defects and

are kept in good repair and working order, e.g. so that the required dimensions remain within permissibletolerance despite wear.

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© ISO/IEC 2011 – All rights reserved 1

Explosive Atmospheres — Part 38: Equipment and componentsin explosive atmospheres in underground mines

1 Scope

This International Standard specifies the explosion protection requirements for the design, construction,assessment and information for use (maintenance, repair, marking) of equipment that may be an individualitem or form an assembly. This includes machinery and components placed on the market by a single supplierfor use in mines susceptible to explosive atmospheres of firedamp and/or combustible dust (at atmospheric

conditions as defined as follows: atmospheric pressure 0,8 bar to 1,1 bar, temperature -20°C to + 60°C, airwith normal oxygen content, typically 21 % v/v).

This International Standard applies for equipment and components according to EPL Mb to be used inpotentially explosive atmospheres containing firedamp and/or combustible dust.

NOTE In some countries, there might be differences according to the classification, e.g. in the European Union Mb issimilar to category M2.

It is necessary to take account of external conditions to the equipment which may affect the hazard and theresultant protection measures. These measures may include ventilation, gas detection or gas drainage.

This International Standard also deals with the prevention of ignitions of explosive atmospheres caused by

burning (or smouldering) of combustible material such as fabric fibres, plastic ”O”-rings, rubber seals,lubricating oils or greases used in the construction of the equipment if such items could be an ignition source.For example, the mechanical failure of rotating shaft bearings can result in frictional heating that ignites itsplastic cage, plastic seal or lubricating grease.

2 Normative references

The following referenced documents are indispensable for the application of this International Standard. Fordated references, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including any amendments) applies.

IEC 60079-0, Explosive atmospheres — Part 0: Equipment — General requirements

IEC 60079-1, Explosive atmospheres — Part 1: Equipment protection by flameproof enclosures "d"

IEC 60079-6, Explosive atmospheres — Part 6: Equipment protection by oil immersion "o"

IEC 60079-11, Explosive atmospheres — Part 11: Equipment protection by intrinsic safety "i"

IEC 60079-25, Electrical apparatus for potentially explosive atmospheres — Part 25: Intrinsically safe systems

IEC 60079-28, Explosive atmospheres – Part 28: Protection of equipment and transmission systems usingoptical radiation

IEC 60204-1, Safety of machinery — Electrical equipment of machines — Part 1: General requirements

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IEC 60204-11, Safety of machinery — Electrical equipment of machines — Part 11: Requirements for HVequipment for voltages above 1000 V a.c. or 1500 V d.c. and not exceeding 36 kV

IEC 60332-1-1, Tests on electric and optical fibre cables under fire conditions — Part 1-1: Test for verticalflame propagation for a single insulated wire or cable — Apparatus

IEC 60332-1-2, Tests on electric and optical fibre cables under fire conditions — Part 1-2: Test for verticalflame propagation for a single insulated wire or cable — Procedure for 1 kW pre-mixed flame

IEC 60332-1-3, Tests on electric and optical fibre cables under fire conditions — Part 1-3 Test for verticalflame propagation for a single insulated wire or cable — Procedure for determination of flamingdroplets/particles

IEC 60529, Degrees of protection provided by enclosures (IP Code)

IEC 62061, Safety of machinery — Functional safety of safety-related electrical, electronic and programmableelectronic control systems

IEV 426, International electrotechnical vocabulary — Chapter 426: Electrical apparatus for explosiveatmospheres

ISO 1940-1:2003, Mechanical vibration — Balance quality requirements for rotors in a constant (rigid) state —Part 1: Specification and verification of balance tolerances

ISO 4413, Hydraulic fluid power — General rules relating to systems

ISO 4414, Pneumatic fluid power — General rules relating to systems

ISO 4952, Structural steels with improved atmospheric corrosion resistance

ISO 7010, Graphical symbols — Safety signs in workplaces and public areas

ISO 8421-1:1987, Fire protection — Vocabulary — Part 1: General terms and phenomena of fire

ISO 13849-1, Safety of Machinery — Safety-related parts of control systems — Part 1: General principles fordesign

ISO 14118:2000, Safety of machinery — Prevention of unexpected start-up

ISO 14935, Petroleum and related products — Determination of wick flame persistence of fire-resistant fluids

ISO 15029-1, Petroleum and related products — Determination of spray ignition characteristics of fire-resistant fluids — Part 1: Spray flame persistence — Hollow-cone nozzle method

ISO/DIS 15029-2, Petroleum and related products — Determination of spray ignition characteristics of fire-resistant fluids — Part 2: Spray test — Stabilized flame heat release spray method

ISO/CD 80079-36:2010-12, Explosive atmospheres — Non-electrical equipment for explosiveatmospheres — Part 36: Basic method and requirements

ISO/CD 80079-37:2010-12, Explosive atmospheres — Non-electrical equipment for explosiveatmospheres — Part 37: Non electrical type of protection constructional safety ‘c’, control of ignition source ‘b’,liquid immersion ‘k’

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3 Terms, definitions and abbreviated terms

For the purposes of this International Standard, the following terms and definitions apply as well as IEC60079-0.

3.1firedamp

any potentially explosive mixture of gases or any flammable gas naturally occurring in a mine

NOTE As firedamp consists mainly of methane, the terms firedamp and methane are used frequently inmining practice as synonyms.

3.2protection against firedamp explosions

explosion prevention and protection in underground parts of mines and those parts of surface installations ofsuch mines liable to be endangered by firedamp and or flammable dust

3.3

flammable substancesubstance in the form of gas, vapour, liquid, solid, or mixtures of these, able to undergo an exothermicreaction with air when ignited

3.4component"component" means any item essential to the safe functioning of equipment and protective systems but withno autonomous function

3.5deflagrationexplosion propagating at subsonic velocity

[ISO 8421-1:1987, 1.11]

3.6detonationexplosion propagating at supersonic velocity and characterized by a shock wave

[ISO 8421-1:1987, 1.12]

3.7equipment"equipment" means machines, apparatus, fixed or mobile devices, control components and instrumentationthereof and detection and prevention systems which, separately or jointly, are intended for the generation,

transfer, storage, measurement, control and conversion of energy, for the processing of material, and whichare capable of causing an explosion through their own potential sources of ignition

3.8explosiona sudden increase of pressure and temperature, due to oxidation or other exothermic reaction

[IEV 426-02-13]

3.9explosion limitslimits of the explosion range

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3.10lower explosion limit (LEL)lower limit of the explosion range

3.11

upper explosion limit (UEL)upper limit of the explosion range

3.12explosion pointslower and upper explosion point

3.13lower explosion pointtemperature of a combustible liquid at which the concentration of the saturated vapour in air is equal to thelower explosion limit

3.14

upper explosion pointtemperature of a combustible liquid at which the concentration of the saturated vapour in air is equal to theupper explosion limit

3.15explosion rangerange of the concentration of a flammable substance in air, within which an explosion can occur

3.16explosion-resistant

property of vessels and equipment designed to be either explosion-pressure-resistant or explosion-pressure-shock resistant

3.17explosion-pressure-resistant

property of vessels and equipment designed to withstand the expected explosion pressure without becomingpermanently deformed

3.18explosion-pressure-shock resistantproperty of vessels and equipment designed to withstand the expected explosion pressure without rupturing,but allowing permanent deformation

3.19explosive atmospherea mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapour, mist ordust in which, after ignition, combustion spreads throughout the unconsumed mixture

3.20flash pointthe lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours inquantity such as to be capable of forming an ignitable vapour/air mixture

[IEV 426-02-14]

3.21hazardous explosive atmosphereexplosive atmosphere which, if it explodes, causes damage

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3.22hybrid mixturemixture of flammable substances with air in different physical states

NOTE Examples of hybrid mixtures are mixtures of methane, coal dust and air or mixtures of gasoline vapour and

gasoline droplets with air

3.23inertingaddition of inert substances to prevent explosive atmospheres 3.24intended useuse of equipment, protective systems and devices in accordance with the equipment group and category asspecified in 3.41, and taking into account all the information supplied by the manufacturer which is required forthe safe functioning of equipment, protective systems and devices

3.24limiting oxygen concentration (LOC)maximum oxygen concentration in a mixture of a flammable substance and air and an inert gas, in which an

explosion will not occur, determined under specified test conditions

3.25machineryassembly of linked parts or components, at least one of which moves, with the appropriate actuators, controland power circuits, etc., joined together for a specific application, in particular for the processing, treatment,moving or packaging of a material (material is equivalent to substance or product)

term "machinery" also covers an assembly of machines which, in order to achieve the same end, are arrangedand controlled so that they function as an integral whole

3.26malfunction

equipment, protective systems and components do not perform the intended function

NOTE For the purposes of this standard this can happen due to a variety of reasons, including

variation of a property or of a dimension of the processed material or of the workpiece;

failure of one (or more) of component parts of the equipment, protective systems or components;

external disturbances (e.g. shocks, vibration, electromagnetic fields);

design error or deficiency (e.g. software errors);

disturbance of the power supply or other services;

loss of control by the operator (especially for hand-held machines).

3.27maximum experimental safe gap (MESG)maximum gap of the joint between the two parts of the interior chamber of a test apparatus which, when theinternal gas mixture is ignited and under specified conditions, prevents ignition of the external gas mixturethrough a 25 mm long joint, for all concentrations of the tested gas or vapour in air. The MESG is a property ofthe respective gas mixture (see also IEC 60050-426)

3.28maximum explosion pressure ( pmax)maximum pressure occurring in a closed vessel during the explosion of an explosive atmosphere determinedunder specified test conditions

3.29maximum rate of explosion pressure rise ((d p /dt )max)

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maximum value of the pressure rise per unit time during explosions of all explosive atmospheres in theexplosive range of a combustible substance in a closed vessel under specified test conditions

3.30minimum ignition energy (MIE)

lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect ignition of the mostignitable atmosphere under specified test conditions

3.31minimum ignition temperature of an explosive atmosphereignition temperature of a combustible gas or of a vapour of a combustible liquid or the minimum ignitiontemperature of a dust cloud under specified test conditions (CH4 560°C)

3.32ignition temperature (of a combustible gas or of a combustible liquid)the lowest temperature of a heated surface at which, under specified conditions, the ignition of a flammablesubstance in the form of a gas or vapour mixture with air will occur

NOTE – IEC publication 79-4 standardizes a method for the determination of this temperature.

[IEV 426-02-01]

3.33minimum ignition temperature of a dust cloudlowest temperature of a hot surface on which the most ignitable mixture of the dust with air is ignited underspecified test conditions (coal dust >> 560°C)

3.34minimum ignition temperature of a dust layerlowest temperature of a hot surface at which ignition occurs in a dust layer under specified test conditions(coal dust 150 °C)

3.35normal operationsituation when the equipment, protective systems and components perform their intended function within theirdesign parameters

minor releases of flammable material may be part of normal operation. For example, releases of substancesfrom seals which rely on wetting by the fluid which is being pumped are considered to be minor releases

failures (such as a breakdown of pump seals, flange gaskets or releases of substances caused by accidents)which involve repair or shut-down are not considered to be part of normal operation

3.36potentially explosive atmosphereatmosphere which could become explosive due to local and operational conditions

3.37protective system"protective system" means design units which are intended to halt incipient explosions immediately and/or tolimit the effective range of explosion flames and explosion pressures. Protective systems may be integratedinto equipment or separately placed on the market for use as autonomous systems

3.38reduced explosion pressure

pressure generated by an explosion of an explosive atmosphere in a vessel protected by either explosion

relief or explosion suppression

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3.39self-ignition of dust in bulkignition of dusts caused by the rate of heat generation from oxidation and/or decomposition reactions of thedust being greater than the rate of heat loss to the surroundings

3.40equipment protection levelEPLlevel of protection assigned to equipment based on its likelihood of becoming a source of ignition anddistinguishing the differences between explosive gas atmospheres, explosive dust atmospheres, and theexplosive atmospheres in mines susceptible to firedamp

NOTE The equipment protection level may optionally be employed as part of a complete risk assessment of aninstallation, see IEC 60079-14.

3.41EPL Mbequipment for installation in a mine susceptible to firedamp, having a "high" level of protection, which has

sufficient security that it is unlikely to become a source of ignition in normal operation or during expectedmalfunctions in the time span between there being an outbreak of gas and the equipment being de-energized

3.42type of protection constructional safety "c"

a type of ignition protection in which constructional measures are applied so as to protect against the possibilityof ignition from hot surfaces, sparks and adiabatic compression generated by moving parts

3.43protection by control of ignition source 'b'device in non-electrical equipment, whereby (an) integral sensor(s) detect(s) impending operation likely to causean ignition of the surrounding atmosphere and initiate either automatic or manual ignition control measures toprevent a potential ignition source becoming an effective ignition source.

3.44liquid immersion ’k’a type of protection in which potential ignition sources are made ineffective or separated from the flammableatmosphere by either totally immersing them in a protective liquid, or by partially immersing and continuouslycoating their active surfaces with a protective liquid in such a way that an explosive atmosphere which may beabove the liquid, or outside the equipment enclosure cannot be ignited.

3.45expected malfunctiondisturbances or equipment faults which normally occur in practice

3.46

rare malfunctiontype of malfunction which is known to happen but only in rare instances. Two independent foreseeablemalfunctions which, separately, would not create an ignition hazard but which, in combination, do create anignition hazard, are regarded as a single rare malfunction

3.47maximum surface temperaturehighest temperature attained in service as determined in ISO/CD 80079-36:2010-12, under the most adverseoperating conditions (but within the recognised tolerance) by any part or surface of equipment, protective systemor component which can produce an ignition of the surrounding explosive atmosphere

NOTE 1 The relevant surface temperature can be internal or external depending upon the type of ignition protectionconcerned.

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NOTE 2 In order to avoid ignition it follows that the maximum surface temperature should be lower than the ignitiontemperature of the explosive atmosphere.

Alternative definition:

the highest temperature attained in service under the most adverse operating conditions within the rating ofthe electrical apparatus by any part or any surface of the apparatus which could produce an ignition of thesurrounding explosive atmosphere

NOTE – The most adverse operating conditions include recognized overloads and any fault conditionrecognized in the specific standard for the type of protection concerned. [IEV 426-01-04]

3.48type of ignition protectiontypes of protection listed in the scope

Alternative definition:

the specific measures applied to electrical apparatus to avoid ignition of a surrounding explosive atmosphereby such apparatus [IEV 426-01-02]

3.49non-electrical equipmentequipment which can achieve its intended function without the use of electrical energy

3.50potential ignition sourceany ignition source which may occur in the equipment

3.51effective ignition source

ignition source which is capable of igniting the explosive atmosphere

3.52mechanical sparks

sparks, as well as showers of sparks, produced by impact or friction between two similar or dissimilar solidmaterials

3.53incendive sparkssparks with sufficient thermal energy to ignite a flammable atmosphere

3.54automatic control measure action taken without manual intervention, to prevent a potential ignition source from becoming an effectiveignition source

3.55manual control measure action taken by a person as a result of a warning, indication, or alarm, to prevent a potential ignition sourcefrom becoming an effective ignition source

3.56ignition prevention system (IPS) arrangement that converts signals from one or more sensors into an action, or indication, to prevent apotential ignition source becoming an effective ignition source

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3.57ignition prevention level (IPL)level assigned to the ignition prevention system characterized by its reliability

3.58

protective liquida liquid which prevents the explosive atmosphere from making direct contact with potential ignition sourcesand thereby ensures it cannot be ignited.

3.59equipment with a sealed enclosuretotally enclosed equipment that prevents the ingress of an external atmosphere during the expansion andcontraction of the internally contained protective liquid during use in service. Such equipment includes anypipework associated with it and may contain an over pressure relief device.

3.60equipment with a vented enclosuretotally enclosed equipment that allows the ingress and egress of an external atmosphere through a breathing

device or constricted opening during the expansion and contraction of the internally contained protective fluidduring normal operation. Such equipment includes any pipework associated with it.

3.61open equipmentequipment that has its components or is itself immersed in a protective liquid that is open to the externalatmosphere. For example, an open top vessel with immersed moving components. Such equipment includesany pipework associated with it.

3.62Hydraulic fluids

all fluids and their concentrates for hydraulic transmission and monitoring with exception of water

4 Requirements for equipment (machines) and components

4.1 General

All electrical and non-electrical equipment and components for use in a potentially explosive atmosphere shallbe designed and constructed to good engineering practice and in conformity with requirements of group I EPLMb equipment to ensure that ignition sources do not occur. Maintenance and testing shall be considered aspart of good engineering practice (see 7.2.2).

To specify the category of the equipment, it shall be subject to a certification in accordance with IEC 60079-0for electrical equipment and subject to an ignition hazard assessment in accordance with 4.2 for non-electrical

equipment.

NOTE 1 Where necessary, to determine any local conditions of use that affect the ignition hazard assessment,negotiations may need to take place between the manufacturer or authorized representative, purchaser and/or user.

NOTE 2 Examples of the ignition hazard assessment for various types of mining machinery have been included in theinformative Annexes A and B. These are based on specific machines, but are not definitive and can contain alternatives.Manufacturers are required to carry out an ignition hazard assessment for each individual machine and determine themost appropriate measures to prevent those ignition sources becoming effective.

In particular, the following requirements according to ISO/CD 80079-36 apply to all machines and shall betaken into account:

the need to restrict the maximum surface temperature;

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the need to meet the electrostatic requirements;

the need to restrict the use of exposed light metals;

the need to perform tests on non-metallic parts on which the ignition protection depends to ensure they

will not deteriorate in the conditions of use in mines and cause the protection to be lost (see also clause6).

NOTE 3 To meet the requirements for maximum surface temperature, the assessment needs to be made at themaximum duty cycle that the equipment is subject to in operation. This can be based on a combination of directmeasurement of the equipment under test, calculation or previous experience.

Equipment may be prevented from exceeding the maximum surface temperature by one, or a combination of,the following measures:

continuous rating of the equipment so that it can easily cope with the maximum duty cycle;

a suitable short-time rating of the equipment;

additional cooling systems;

shut-down devices measuring the temperature of either the surface or the cooling system;

limitation of power transfer through the equipment, e.g. current limitation of motor supply ordisengagement of mechanical power.

Where the means of limiting the surface temperature is not by continuous rating, the manufacturer has tospecify the special conditions of safe use in the user instructions, e.g. maximum oil temperature at which theequipment is automatically de-energized.

NOTE 4 Welding, cutting, grinding, burning and other processes involving naked flames and/or open sparking arenormally prohibited in coal and other gassy mines unless special precautions are taken. Machines intended for use inpotentially explosive atmospheres should therefore be constructed so that such processes are not normally required toassemble, dismantle, maintain or repair machinery underground in a gassy mine.

In addition to the requirements for non-metallic materials specified in IEC 60079-0 and ISO/CD 80079-36,where such materials can be an ignition source, they shall be fire-resistant (see 6.2).

4.2 Ignition hazard assessment

4.2.1 Formal analysis

All equipment and all parts of it shall be subjected to a formal documented hazard analysis that identifies and

lists all of the potential sources of ignition by the equipment and the measures to be applied to prevent thembecoming effective. Examples of such sources include hot surfaces, naked flames, hot gases/liquids,mechanically generated sparks, adiabatic compression, shock waves, exothermic chemical reaction, thermitereactions, self ignition of dust, electrical arcing and static electricity discharge.

Protective measures/types of protection shall be considered and/or applied in the following order:

ensure that ignition sources cannot arise;

ensure that ignition sources cannot become effective;

prevent explosive atmosphere reaching the ignition source;

contain the explosion and prevent flame propagation.

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The assessment shall list all of the potential ignition sources that are either effective or likely to become effective,in normal operation. It shall also list those sources where the risk of them becoming effective cannot bedisregarded by virtue of the equipment being designed to be de-energised in the event of an explosiveatmosphere occurring. The assessment shall indicate the measures to prevent the ignition used according to thisstandard and to the ignition protection standards listed in the scope of this standard which have been applied to

render such ignition sources ineffective during the period from the occurrence of the explosive atmosphere, itsdetection and the de-energisation of the equipment.

4.2.2 Assessment with faults

The assessment for malfunction shall include those components which, if they failed, could ignite any flammablesubstance (e.g. lubricating oil) contained within the equipment and which could consequently become or createan ignition source.

4.2.3 Establishing the maximum surface temperature

As part of the assessment, the maximum surface temperature of the equipment has to be established. This isthe highest surface temperature of any part of the equipment that could be exposed to the potentially explosiveatmosphere, or where a dust layer could form, taking account of its size and ability to become an ignition source.The assessment shall also take account of any integral device(s) fitted to limit the maximum surface temperature(e.g. the use of a low melting point fusible drain plug in a fluid coupling).

The measurement, or determination by calculation, of the maximum surface temperature shall be made with theequipment at full load, but with those failures tolerated by the applied type of ignition protection.

4.2.4 Dust deposits and other material in the gap of moving parts

The ignition hazard assessment shall consider the ignition risk that arises from dust or other material trappedbetween two moving parts or a moving part and a fixed part. If dust or other material remains in contact with thesame moving part for a long period, it can heat up and can cause a burning deposit of dust or other material

which can later ignite a dust cloud. Even slow moving parts can cause a large rise in temperature.

4.2.5 Ignition hazard assessment report

The assessment document will differ according to the different equipment groups and categories of equipment ina particular group. The results of the ignition hazard assessment shall include as a minimum, information on allpotential ignition sources, the measures which have been applied to prevent the sources becoming effective,and the ignition protection used. The results shall include a record in a tabular form as shown in Figure 1 below.

Potential ignition source Measures applied to prevent thesource becoming effective

Ignition protection used

( 1) (2) (3)

Figure 1 — Assessment table for Group I equipment

NOTE By definition, EPL Mb equipment is required to incorporate a high level of ignition protection irrespective of thefact that it is intended to be de-energised in the event of an explosive atmosphere. This means that ignition protection canhave to be applied to some potential sources where, although not present in normal operation, the risk of them becomingeffective cannot be discounted.

The hazard assessment report shall be included in the required technical documentation which demonstratescompliance with this standard.

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4.2.6 Ignition sources

The ignition capability of the ignition source shall be compared with the ignition properties of the flammablesubstance.

The likelihood of occurrence of the effective ignition sources shall be assessed, taking into account those thatcan be introduced e.g. by maintenance and cleaning activities.

NOTE Protective measures can be used to make the ignition source non-effective.

If the likelihood of occurrence of an effective ignition source cannot be estimated, the assumption shall bemade that the ignition source is present at all times.

The different ignition sources are to be considered as follows. Detailed requirements see Annex C.

Hot surfaces

Flames and hot gases (including hot particles)

Mechanically generated sparks

Electrical apparatus

Stray electric currents

Static electricity

Lightning

Radio frequency (RF) electromagnetic waves from 104 Hz to 3 × 1012 Hz (high frequency)

Electromagnetic waves from 3 × 1011 Hz to 3. × 1015 Hz

Ionizing radiation

Ultrasonics

Adiabatic compression and shock waves

Exothermic reactions, including self-ignition of dusts

4.3 Non-electrical equipment and components

All non-electrical equipment and components (including parts used within the machine in order to connectthem), shall comply with the requirements of ISO/CD 80079-36 and, where necessary, one of the other typesof ignition protection listed in that standard, except where specific requirements exist in this InternationalStandard, e.g. the fitting of water spray ignition protection to cutting picks.

NOTE 1 ISO/CD 80079-36 deals with ignition protection of non-electrical equipment and components intended for usein both potentially explosive gas atmospheres and potentially explosive dust atmospheres, existing either separately, orcombined.

NOTE 2 Examples of ignition protection standards particularly relevant to mining are:

Protection by constructional safety ‘c’ (see ISO/CD 80079-37);

Protection by control of ignition sources 'b' (see ISO/CD 80079-37);

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Protection by liquid immersion ‘k’ (see ISO/CD 80079-37).

4.4 Electrical equipment and components

4.4.1 General

Electrical equipment and components shall be of rugged construction in accordance with the application andbe designed in a manner that will facilitate testing and maintenance. They shall be well constructed, based onsound engineering principles and suitable for their intended use.

All electrical equipment and components shall comply with the requirements of IEC 60079-0 and at least oneof the types of ignition protection listed in that standard.

NOTE 1 IEC 60079-0 deals primarily with the ignition protection of electrical equipment and components intended foruse in potentially explosive gas atmospheres. For gassy mines, equipment tested in an explosive gas atmosphere andprotected against igniting firedamp is also adequately protected against ignition of an explosive coal dust cloud.

NOTE 2 Examples of ignition protection standards particularly relevant to mining are:

IEC 60079-1 (Flameproof enclosure "d");

IEC 60079-7 (Increased safety "e");

IEC 60079-11 (Intrinsic safety "i").

As a general rule, electrical equipment on machines shall comply with IEC 60204-1 and IEC 60204-11, exceptwhere the differences are stated in the following clauses of this International Standard.

Where protective measures depend on devices external to the machine, the manufacturer shall specify thesein the user instructions. For the purposes of this International Standard, the requirements below commence at

the point where the electrical supply is connected to the machine (terminals, plug and socket).

NOTE 3 All terms used to describe electrical devices are as defined in IEC 60050-441.

4.4.2 Electrical equipment protection

When electrical equipment is used in a potentially explosive atmosphere, the conditions of use specified in thecertificate of conformity to IEC 60079–0 shall be complied with.

NOTE Typical conditions for safe use might, for example, include the minimum flow of cooling water, temperatureprotection settings, duty cycle (short time rating).

4.4.3 Overcurrent protection

4.4.3.1 Overload protection

For the protection of motors and their supply cables against overloading, the requirements of IEC 60204-1 andIEC 60204-11 shall apply.

NOTE 1 The objective is to ensure that the maximum surface temperature is in accordance with IEC 60079-0.

Possible overloads or temperature rises may be caused by:

a) high starting frequency;

b) starting under load.

Motors that are likely to be overloaded shall additionally be protected by temperature monitoring devices.

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The setting of the overload tripping device may be above the nominal current of the motor if it is monitored bydirect temperature monitoring, in accordance with the certificate of conformity to IEC 60079–0.

NOTE 2 Such direct temperature monitoring is typically achieved by locating temperature sensors in the motor statorwindings, near to the bearings.

Protection against overload shall be achieved by the use of fuses, directly-operating trip relays, current-transformer-operated trip relays or thermal trip devices, etc. Depending on the system, combinations of theabove might be required.

Overload protection shall not be provided if:

a hazard is caused by its operation, e.g. the prevention of high voltages on secondary windings of currenttransformers, or tripping of exciter windings in generators or synchronous motors, or electrical brakingcircuits and

its exclusion is in accordance with the certificate of conformity to IEC 60079–0.

Overload protection devices shall be installed at the beginning of each circuit and at positions where thecurrent-carrying capacity of a conductor is reduced.

4.4.3.2 Short-circuit protection

Short-circuit protection shall be provided to protect in the event of a short-circuit occurring in any part of thecircuit being protected except IS circuits (see IEC 60079-11).

Short-circuit protection may be incorporated in or external to the electrical equipment.

Facilities to prevent resetting by unauthorized persons shall be provided.

All external cables installed on a mobile machine shall be provided with short-circuit protection that willadequately protect the smallest cross section area cable that it is protecting.

4.4.4 Earth-fault protection

The requirements of IEC 60204-1 and IEC 60204-11 shall apply insofar as they describe shock-hazardprotection and include automatic disconnection of the supply if an insulation fault occurs.

NOTE 1 The specific design depends on network configuration and should allow for connection to a disconnecting device

that automatically interrupts the power supply to a machine if either the insulation of a supply cable is faulty or a fault

occurs in the machine circuits. Information should be provided in the user instructions about the connection of the machine

to the electrical system of the mine.

All enclosures and exposed metallic parts of electrical equipment and components capable of igniting afiredamp/air atmosphere or a coal dust/air cloud shall be electrically connected together and to a continuousprotective conductor (individual external conductor or integrated into a multi-core cable).

Earth-fault protection shall be provided by either a) or b) below:

a) the protection shall be designed such that when one phase is connected to earth (protectiveconductor) in a system having near infinite insulation resistance, the protection system shall operatewhen the earth- fault current attains a value greater than 20 % of the prospective earth-fault current,or

NOTE 2 For mines having a potentially explosive atmosphere, the connection between the protective conductor andthe other conductors will usually have an earth-fault current restricting device fitted in order to limit the maximum

prospective earth current in the power system to a value below that specified in national legislation.

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b) the insulation resistance between live conductors and the protective conductor shall be monitored. Thedesign of the earth-fault monitoring device shall ensure that faulty components in the circuit aredisconnected.

The reconnection of power to the equipment while an insulation fault persists shall be prevented.

In the case of battery-powered traction vehicles and vehicles with on-board starter batteries, the insulationlevel between the vehicle frame or earth or bonded metallic parts and the positive and negative poles shall becontinuously monitored. Indication shall be given to the vehicle operator if the insulation level between anypole and the vehicle frame, earth or metallic parts falls to a level below a fixed value.

NOTE 3 Permissible values are stipulated in national legislation.

4.4.5 Mechanical protection of live parts

All electrical equipment on machines, including cables and components shall protected against all forms ofdamage expected in mining conditions (impact, rubbing, crushing) which could cause an ignition risk, e.g. anarc resulting from a short-circuit of live conductors.

4.4.6 Electric cables that are part of the equipment

4.4.6.1 Cable arrangements

All external cables installed on a mobile machine shall be

a) arranged clear of moving parts;

b) provided with short-circuit protection that will adequately protect the smallest cross section areacable that it is protecting;

c) protected from hot surfaces that may adversely affect the insulation of cables and moving parts;

d) arranged so as to prevent excessive bending or twisting;

e) clamped in place to prevent undue movement;

f) protected from mechanical damage by being correctly positioned;

g) protected from abrasions caused by movement of hydraulic lines;

h) of the same temperature rating as the environment in which they are installed.

4.4.6.2 Cable protection hoses

Where cables are mechanically protected by cable protection hoses the hoses shall be flame resistant anti-static. Consideration should be given to the identification of hoses and to differentiate between electrical andother applications, e.g. hydraulics.

4.4.6.3 Cables used in intrinsically safe systems

Cables used in intrinsically safe systems shall comply with IEC 60079-11 and IEC 60079-25.

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5 Additional requirements for specific equipment and components

5.1 Cutting and stripping equipment

5.1.1 General

Where there is a risk of the cutting picks igniting the atmosphere, they shall be designed so as to minimize therisk of frictional heat and/or sparks.

NOTE 1 The risk of ignition by the cutting picks is usually associated with the following conditions:

a) an ignitable concentration of firedamp may occur in the cutting zone around the picks;

b) the strata that might be contacted contains quartz;

c) the strata contain deposits of pyrites.

In selecting the type of cutting picks - to minimize frictional sparking - the user instructions shall specify:

the type of picks to be used;

their acceptable wear limits;

a safe method of pick replacement;

a requirement that the user determines a checking frequency.

Interlocks shall have a performance level (PL) in accordance with ISO 13849-1 or a safety integrity Level (SIL)in accordance with IEC 62061.

NOTE 2 The interlocks are not all required on all machines, but the information provides a guide to what may berequired on individual machines.

5.1.2 Machines with cutting picks

5.1.2.1 General

Any machine intended to be used under the conditions described in 5.1.1 shall incorporate a system that hasbeen proven by testing to provide ignition protection. This system shall have either ventilation to the cuttingzone or water sprays to the cutting picks or a combination of both. The effectiveness of the protection systemshould be validated by the manufacturer and operating parameters determined and specified in the userinstructions. The minimum water pressure and/or flow should be specified by assessing the ignition riskaccording to 4.2.

5.1.2.2 Water spray systems

Where these systems are used, the machines shall incorporate a water spray system directed at the cuttingpicks. It also includes a device for monitoring the pressure and/or water flow to the spray system. An interlockshall be connected into the machine control circuit to prevent the rotating cutting tools from operating unlessthe minimum pressure and/or flow of water is present in the water spray system.

The above does not apply to end-ring picks of shearer loaders that cannot be sprayed.

NOTE Research has shown that the most likely ignition location within the cutting zone is at the rear of the cuttingpick where hot particles or surfaces occur.

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5.1.2.3 Air dilution systems

Where these systems are used, machines shall incorporate a means to dilute combustible gases around thecutting picks. In these cases, a disconnection device shall be provided to either continuously monitor the airflow or the equipment that produces it. An interlock shall be connected to machine monitoring circuit to

prevent the cutting picks from being operated before there is a minimum amount of air in the cutting zone

5.1.3 Stripping machines

Stripping machines, such as ploughs, shall have an interlock arranged so that they cannot be started unless awater spray system is operating. Such spray systems may be positioned either at, or on, the stripping head orapplied to the particular section of the face being mined.

5.2 Rope haulages for level and inclined transport

For rope-hauled systems for level and inclined transport systems, excessive heat caused by frictional slippingbetween the haulage ropes and the drive pulley wheel/drum shall be avoided, for example, by maintaining the

correct tension on the rope using a suitable rope tensioning device.

For endless rope systems, at least 2,5 laps of rope or a larger number of laps if specified by the manufacturershall be maintained on the drive pulley wheel/drum.

The user instructions shall include information about the correct positioning and siting of idler rollers, guiderollers and runners and any other precautions needed to avoid seizure by contamination from water, dust anddirt.

The user instructions shall include information on the recommended inspection intervals necessary todetect/observe impending roller failures.

5.3 Fans

5.3.1 Ventilating fans for use underground

5.3.1.1 General

Ventilating fans for underground use may also be used for cooling and dust removal.

Fan casings shall be rigid and capable of withstanding without deformation the loads and impacts that mightnormally be encountered in mining operations. They shall be made from mild steel in accordance with ISO4952 and the minimum material thickness shall be 5 mm.

5.3.1.2 Bifurcated and centrifugal fans

Bifurcated fans with casings having a material thickness of less than 8 mm shall have additional strengtheningin the form of roll bars or similar means.

Casings of mixed flow or centrifugal bifurcated or volute fans shall have a separate inlet cone which shall beadjusted to suit the impeller position, securely fixed and then locked in position by two offset spiral dowel pins.

5.3.1.3 Inlet and outlet cones

Inlet cones for mixed flow and centrifugal fans shall be rigid and constructed to a tolerance of ± 1,5 mm ondiameter.

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5.3.1.4 Impellers and impeller rings

Impellers shall be designed and constructed to minimize locations where a build-up of combustible dust mightoccur.

5.3.1.5 Clearance

For bifurcated and axial fans having the motor bolted into the casing with the impeller attached, the radialclearance shall be specified in the user instructions.

For bifurcated and axial fans, the minimum axial clearance shall be 1,5 mm between the impeller and thecasing. If materials other than those of low ignition risk are used, the clearance between rotating and staticparts shall be not less than 1/250 of the casing diameter, but need not exceed 5 mm. Inlet cones may beconstructed entirely from materials of low ignition risk (see Table 1).

5.3.1.6 Balancing

Impellers shall be balanced and corrections made by fixing an appropriate mass to the impeller. Beforebalancing, the impeller shall be in a clean condition and free of rust and scale. Once the impeller is fitted to theactual motor rotor, the rotating parts of the completed fan shall have a balance quality better than G 6,3 asdescribed in ISO 1940-1:2003.

5.3.1.7 Overheating of the fan motor

At an air density of 1,4 kg/m3, the power required to drive the fan at the point on the fan characteristic curve

with the steepest possible impeller blade setting shall not exceed the appropriate motor power given on therating plate.

5.3.1.8 Materials

In order to minimize the risk of ignition by sparking between impeller and fan casing, all fan casings shall beprovided with static rings of low ignition risk material according to Table 1 at potential rubbing points. Theclearances between the impellers and fixed parts of casings or inlet cones shall not be less than those shownin Table 1.

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Table 1 — Combination of materials

Material used for therubbing track

Material used for the impeller

AlSi10Mg(a)

EN AB 43000a

AlSi12(a)

EN AB 44200a

Cu Zn 39b High grade steel

X 5 CrNi 18 9

AlSi10Mg(a)

EN AB 43000a

(1) (1) (1) (3)

AlSi12(a)

EN AB 44200a

(1) (1) (3) (3)

Cu Zn 39b (1) (1) (3) (2)

High grade steel

X5 CrNi 18 9

(3) (3) (3) (3)

Steel S235JRc (3) (3) (3) (3)

Low ignition risk for:

(1) Combination of materials with low ignition risk:

radial clearance 1 mm or 1/1 000 of the impeller diameter, whichever is the greater.

(2) Combination of materials with low ignition risk:

radial clearance 1,5 mm

For both cases, the rubbing track rings shall be formed with a thickness of not less than 3 mm.

(3) Combination of materials with higher ignition risk:

radial clearance at least 1/250 of the impeller diameter, but need not exceed 5 mm.

NOTE The use of these light alloys in this application reduces the risk of ignition. National legislation

may restrict some of these combinations of materials.

a See EN 1676 (No International Standard available)

b See EN 12163 (No International Standard available)

c

See EN 10025-2 (No International Standard available)

5.3.2 Other fans

Fans used typically on machines for cooling and/or dust extraction shall comply with the followingrequirements:

the inlet to the fan shall have ingress protection against solid objects to at least IP2X as defined inIEC 60529;

the outlet of the fan shall have an ingress protection of at least IP1X according to IEC 60529;

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in normal operation the clearances, taking into account design tolerances, between the rotating bladesand any fixed parts e.g. the hood, cowling or ventilation screens, shall be at least 1/100 of the maximumdiameter of the fan. These clearances need not exceed 5 mm and may be reduced to 1 mm if theopposing parts are manufactured so as to have dimensional accuracy and stability. In no case shall theclearance be less than 1 mm;

where plastics are used for parts of the fan, the thermal stability of the plastics material shall exceed themaximum temperature to which the material is subjected in service by at least 20 K.

5.4 Diesel engines

5.4.1 General requirements

Diesel engines used in potentially explosive atmospheres in mines shall be explosion protected and complywith the requirements as follows. Internal combustion engines for use in underground workings susceptible tofiredamp and/or combustible dust shall be designated by:

engine group I,

the category (EPL Mb),

the temperature given in 5.4.2.

NOTE The following standards can be used to ensure explosion protection:

EN 1834-2 or AS/NZS 3584.2, AS/NZS 3584.3, AS/NZS 2784

USA recent regulations refer to 30 CFR 36.23, 36.25, 36.27, 36.31, 36.32, 36.48, 36.50.

The main sources of ignition by Diesel engines are:

Hot surfaces,

Flames and hot gases,

Mechanically generated sparks,

Electrical apparatus and systems,

Static electricity.

No ignition of the explosive atmosphere outside the enclosure by hot surfaces, hot gases, flames, sparks orelectrical apparatus shall occur.

Machines fitted with combustion engines shall be equipped with portable fire extinguishers and, wherenecessary, an automatic fire extinguishing system to satisfy clause 4.2. If the fire extinguisher is not suppliedby the manufacturer, the manufacturer's instructions shall specify the type of fire extinguisher. Automatic shutdown shall be provided for engine overspeed. Provision for manual override may be suppliedfor the case of the vehicle being used for emergency escape. Automatic means shall be provided to give analarm for the conditions mentioned below. Shutdown of the engine or a combination of alarms and shutdownmay be provided subject to applications.

Shut down shall be fail to safety. It shall not be possible to restart the engine until the shutdown system hasbeen manually reset.

Conditions for automatic shut down or otherwise automatic protection of the engine:

Coolant over-temperature in the liquid cooled system;

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Low lubricating oil pressure;

Low water level in cooling system;

Low water level in water based flame arresters;

Over-temperature of the exhaust gas;

High surface temperature for air cooled engines;

High engine oil temperature;

High hydraulic oil temperature.

In addition to these conditions and this clause of this International Standard, the engine shall also be shutdown automatically in the event of actuation of any on-board automatic fire extinguisher. Alternatively, whereloss of engine power may result in loss of power steering etc., the engine may be reduced to idling rather than

be shut down. The fire extinguishing system shall cover the combustion engine and other parts of the machineat risk from fire.

It shall also be possible to discharge them manually and from control consoles on the machine.

Provision should be made for recording of engine system functions by data logging. Such provisions couldinclude engine stop (shutdown) function, engine revolutions, driver details, service and maintenance data.

5.4.2 Flames and hot gases

To avoid overspeeding and/or overheating of the engine caused by firedamp entering the intake air system orby an engine defect, a monitoring and control system shall be provided on the engine. The time delay from thepoint of methane detection to the point of engine shutdown and stop shall be such that it does not create a

hazard to endanger personnel. The system shall ensure that any exposed surface does not exceed themaximum surface temperature and shall be arranged to stop the engine automatically if the permissible levelsspecified by the manufacturer are exceeded.

As an alternative, and if supported by the ignition hazard assessment (see 4.2), the engine may be reduced toidling rather than shut down in the case of excessive coolant temperature or of excessive exhaust gastemperature.

NOTE This is usually achieved by monitoring the cooling water temperature, exhaust gas temperature or lubricatingoil temperature.

The exhaust system is always considered to discharge into a hazardous area. Each exhaust system shall befitted with a flame arrester and a spark arrester.

The maximum surface temperature shall not exceed 150 °C. For underground workings without combustibledust this maximum temperature shall not exceed 450 °C.

5.4.3 Mechanically generated sparks

Fuel tanks shall be of metallic construction, protected against corrosion, and shall be mounted in such aposition as to be protected from mechanical damage. The tank shall pass a tightness test at a pressure of atleast 20 kPa.

The use of light metal alloys shall be minimized. For externally accessible components which may causeignition by impact or friction, metallic materials shall not contain, by weight more than 15 % in total of

aluminium, magnesium, titanium and zirconium and more than 7,5 % in total of magnesium, titanium andzirconium. Components exceeding these limits, shall only be used if they are guarded or protected by a

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suitable anti-incendive sparking coating e.g. a coating of 0,1 mm thick zinc hot sprayed base and 2 coats ofzinc silicate paint or equivalent to prevent impact and friction sparks. Paints and coatings shall not containmore than 15 % by weight in total of the metals aluminium, magnesium, titanium or more than 6 % in total ofmagnesium and titanium. Only paints and coatings of high durability shall be used. Maintenance informationshall be made available to maintain the durability of the paint to prevent exposed light metal alloy.

Rotating components external to the engine (e.g. fan hubs, fan blades, pulleys) shall not be of light metal.

5.4.4 Electrical apparatus and systems

Equipment constructed according to IEC 60079-6 shall not contain flammable oil.

The electrical equipment installation for engines shall be bipolar with the exception that the electrical circuit fora glow plug or other electrical start aid may use the engine cylinder block as part of the earth return circuit forthe period during which the start aid circuit is in operation. When not in operation both positive and negativeconnections shall be isolated from the power supply. For mobile equipment, conventional electric starters mayalso be used provided the electrical supply is off-engine and sited such that the starter can be used only in anon-hazardous area.

5.4.5 Static electricity

Plastic materials shall only be used for external parts if there is no possibility of ignition by electrostaticdischarge.

This is achieved if:

the surface resistance does not exceed 109 measured in accordance with or

the electrostatically chargeable surface area is limited to 100 cm2 or

the thickness of the non conducting material over the conducting layers or metal gauze is not greater than2 mm. When metal gauze is used for the conducting layer the mesh width shall not exceed 100 cm

2.

All external and accessible parts surfaces shall be electrically bonded to the engine cylinder block in order toreach potential equalisation. It is not necessary to connect parts by means of a separate conductors if theseparts are firmly secured and are in metallic contact with the cylinder block.

5.4.6 Electrical protection

The following protection shall be provided:

a) The electrical supply systems shall use a return conductor and shall not be connected to the frame of

the vehicle.

b) Auto reset protection systems shall not be permitted.

c) Protection shall be provided to detect any insulation failure between active conductors and themachine frame. All sources of supply shall be disconnected to the point of fault.

d) All electrical wiring shall be fully enclosed to provide protection. Cables used in intrinsically safesystems located in engine compartments may be excluded if it is installed in a manner which guardsagainst potential damage from the environment in which it is installed.

NOTE Flame resistant antistatic hose, armoured cable or metal conduit is considered adequate.

e) Alternators shall be fitted with integral protection that detects and acts upon leakage to frame, shortcircuits between active conductors, intermittent faults and overvoltage.

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f) The output of the alternator shall be automatically regulated to maintain voltage within the rating ofthe load; e.g. lights, electronic control systems.

g) Where under voltage may cause a hazard, protection shall be provided.

5.5 Air compressors

The input driving power to a compressor shall be interrupted automatically if the temperature of any exposedpart exceeds the maximum surface temperature (normally 150 °C at every stage of pressure increase). In thecase of multi-stage compressors, the temperature shall be measured at every stage of pressure increase andat the discharge air outlet.

NOTE 1 All parts of the compressor that are subject to oil residues and other deposits could be a significant ignitionrisk. Regular maintenance should be carried out according to the manufacturer's instructions.

NOTE 2 The methane content of compressed air should be considered.

Where oil injection is used on a compressor, the air temperature shall be limited to 100 °C at every stage of

pressure increase.

5.6 Drilling equipment and components

Where drilling equipment and components are to be used in circumstances where there is a likelihood of therebeing an ignition risk between the drilling tools and the material being drilled, the manufacturer shall ensurethat the drilling machine and drilling tools are not capable of creating hot surfaces or sparks. To achieve this,the following shall apply:

a) all drilling rods, drilling bits and power transmission connections on hammer and rotary drills shall bepositively engaged and driven by means other than friction so as not to be capable of producingsurface temperatures that are an ignition risk;

b) if the ignition hazard assessment according to 4.2 results in an ignition hazard, all drilling bits of thedrilling equipment exceeding 3 kW drive power shall be provided with either mud flushing, waterflushing or air flushing to both cool the drilling bit and remove drill cuttings from the borehole;

c) the hardness and wear limits of the drilling tools shall be given in the user instructions, based on thetype of use.

5.7 Brakes

5.7.1 Brakes used only for stopping in emergency

Brakes, designed to be used only for emergency stopping of equipment, shall be constructed to allow for themaximum kinetic energy to be dissipated, neither shall the maximum surface temperature be exceeded norshall incendive sparks be generated at any part exposed to the potentially explosive atmosphere.

NOTE For a low likelihood of response of an emergency stopping device the hazard assessment according to 4.2can come to the result that no further means of protection relating to equipment in this category are necessary.

5.7.2 Service brakes (including friction brakes and fluid based retarders)

Service brakes shall be constructed to allow for the maximum kinetic energy to be dissipated so that neithershall the maximum surface temperature be exceeded nor shall incendive sparks be generated at any partexposed to the potentially explosive atmosphere.

NOTE It will frequently be strongly recommended to take other protective measures to prevent sources of ignitionfrom developing.

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5.7.3 Parking brakes

Parking brakes shall be fitted with an interlock which prevents the drive power being applied if the brake is notfully released. Alternatively a control device shall be fitted.

5.8 Traction batteries, starter b

Documents

BS EN 80079-34