As the explosion protection of equipment, protective systems and components depends on: — the design and construction of the equipment, protective systems and components; — the intended
General
In addition to EN 1127-1:2011, 4.1 the following shall apply:
In assessment of the likelihood of occurrence of a hazardous explosive atmosphere in mines, the main factors are:
— the properties of the mineral being worked;
— the manner of working it;
— the presence of firedamp in the immediate strata;
— the effects of human action on the strata in the vicinity of the mine workings;
— the degree of dilution by the ventilation system
NOTE For further information see EN 13478.
Identification of explosion hazards
Identification of ignition hazards
Estimation of the possible effects of an explosion
In addition to EN 1127-1:2011, 4.4 the following shall apply:
The expected injury to persons or damage to objects and the size of the endangered place can thus be estimated only for each individual case
The likelihood and impact of an explosive atmosphere differ across mines, influenced by factors such as the mine type, layout, the minerals extracted, and the potential presence of firedamp or combustible dust.
Hot surfaces
The requirements of 5.1 of EN 1127-1:2011 apply, but special consideration shall be given to hot surfaces of internal combustion engines
For protective measures against ignition hazards from hot surfaces, see 6.4.2.
Flames and hot gases (including hot particles)
The requirements of 5.2 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to flames and hot gases, see 6.4.3.
Mechanically generated sparks
The requirements of 5.3 of EN 1127-1:2011 apply During the cutting of mineral, sparks can be generated and are very often a source of ignition
For protective measures against ignition hazards due to mechanically generated sparks, see 6.4.4.
Electrical equipment
The requirements of 5.4 of EN 1127-1:2011 apply During shot firing, electrical sparks can be generated by the blasting machine and/or detached cables and leads at the time of ignition
For protective measures against ignition hazards due to electrical equipment, see 6.4.5.
Stray electric currents
Stray currents can flow in electrically conductive systems or parts of systems
— as return currents in power generating systems;
— as a result of a short-circuit or of a short-circuit to earth owing to faults in the electrical installations;
— as a result of magnetic induction (e.g near electrical installations with high currents or radio frequencies, see also 5.8);
— as a result of lightning (see 5.7) and
— as a result of induction from surface overhead lines
Disconnection, connection, or bridging of system components that can carry stray currents, even with minor potential differences, can lead to the ignition of an explosive atmosphere through electric sparks or arcs Additionally, ignition may also result from the heating of these current paths.
For protective measures against ignition hazards due to stray electric currents, see 6.4.6.
Static electricity
The requirements of 5.6 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to static electricity, see 6.4.7.
Lightning
The requirements of 5.7 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to lightning, see 6.4.8.
Radio frequency (RF) electromagnetic waves from 104 Hz to 3 × 1011 Hz (high frequency)
The requirements of 5.8 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to electromagnetic waves in the RF spectrum, see 6.4.9.
Electromagnetic waves from 3 × 1011 Hz to 3 × 1015 Hz
The requirements of 5.9 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to electromagnetic waves in this spectral range, see 6.4.10.
Ionizing radiation
The requirements of 5.10 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to ionizing radiation, see 6.4.11.
Ultrasonics
The requirements of 5.11 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to ultrasonics, see 6.4.12.
Adiabatic compression and shock waves
The requirements of 5.12 of EN 1127-1:2011 apply
For protective measures against ignition hazards due to adiabatic compression and shock waves, see 6.4.13.
Exothermic reactions, including self-ignition of dusts
The requirements of 5.13 of EN 1127-1:2011 apply In mines, special attention shall be paid to the self-ignition of coal at all times
For protective measures against ignition hazards due to exothermic reactions, see 6.4.14
Fundamental principles
The simultaneous presence of an explosive atmosphere and an effective ignition source, along with the anticipated effects of an explosion, underscores the three fundamental principles of explosion prevention and protection The first principle is prevention.
To prevent or minimize explosive atmospheres, it is essential to either lower the concentration of flammable substances to levels outside the explosion range or reduce the concentration of oxygen below the limiting oxygen concentration (LOC).
2) avoid any possible effective ignition source This is achieved by a suitable design of the equipment, protective systems and components;
To ensure safety in environments with explosive concentrations, it is crucial to de-energize equipment that contains an ignition source Additionally, implementing protective measures can help limit the effects of explosions to acceptable levels These constructional protective measures are designed with the understanding that a starting explosion may occur.
The elimination or minimization of risk can be achieved by applying one or more of the above prevention or protection principles
The avoidance of an explosive atmosphere shall always be the first choice
The more likely the occurrence of an explosive atmosphere is, the higher the extent of measures against effective ignition sources shall be and vice versa
To allow selection of the appropriate measures, an explosion safety concept shall be developed for each individual case
When planning explosion prevention and protection measures, it is essential to consider normal operations, including start-up and shut-down processes Additionally, potential technical malfunctions and foreseeable misuse must be addressed, as outlined in EN ISO 12100 Implementing effective explosion prevention and protection strategies necessitates a comprehensive understanding of the relevant factors and considerable experience, making it highly advisable to consult with experts in the field.
Avoidance or reduction of explosive atmosphere
Process parameters
6.2.1.1 Substitution or reduction of the amount of substances capable of forming explosive atmospheres
To enhance safety, flammable substances like mineral oil used for machine lubrication should be substituted with non-flammable alternatives or materials that do not create explosive atmospheres For instance, employing "water-in-oil emulsions" for hydraulic roof supports is a safer option compared to traditional mineral oil.
As far as reasonably practicable, the amount of flammable material shall be reduced to the minimum, e.g by firedamp drainage or by dust control measures
The content of firedamp in the air can be substantially reduced by firedamp drainage before and during winning operations
To prevent or limit the formation of hazardous explosive atmospheres around equipment and components, it is essential to implement measures that control the amount and concentration of substances capable of creating such environments.
These measures shall be monitored if the concentrations inherent in the process are not sufficiently outside the explosion range
Such monitoring, e.g gas detectors or flow detectors, shall be coupled to alarms, other protective systems or automatic emergency functions
To ensure safety, it is crucial that the concentration of flammable substances remains well below the lower explosion limit outside of equipment Inside equipment, such as firedamp drainage pipes, flammable substance concentrations must also be kept outside the explosion range Additionally, precautions should be implemented to reduce risks during the startup and shutdown phases of the process, as these are times when concentrations may approach the explosion range.
To effectively limit dust concentration, it is essential to eliminate dust at its source through methods such as exhaust ventilation or water spraying, and to immobilize deposited dust by incorporating hygroscopic substances.
1) use of systems with pressurized apparatus in accordance with EN 60079-2;
2) the addition of inert gases (e.g nitrogen, carbon dioxide) can prevent the formation of explosive atmospheres (inerting);
3) inerting by the use of inert gases is based on reduction of the oxygen concentration in the atmosphere so that the atmosphere is no longer explosive The highest permissible oxygen concentration is derived by applying a safety factor to the limiting oxygen concentration;
4) for mixtures of different flammable substances, including hybrid mixtures, the component with the lowest limiting oxygen concentration shall be used in the determination of the highest permissible oxygen concentration, unless measurements have shown otherwise b) Outside equipment:
1) for hazardous situations, such as fire fighting or preventing spontaneous combustion, the techniques described for inside equipment may also be used for outside equipment;
2) explosive dust-air mixtures can also be made inert by adding a compatible inert dust
NOTE In general, this is achieved by timely addition of a sufficient amount of limestone dust to the deposited dispersible coal dust The necessary amount is specified in national legislation
Design and construction of equipment, protective systems and components containing
During the equipment planning phase, it is crucial to ensure that protective systems and components containing flammable substances are maintained within closed systems at all times This includes systems such as firedamp drainage, dust extraction, and diesel fuel tanks.
Non-flammable or fire-resistant materials shall be used wherever possible (see EN 13478)
6.2.2.2 Minimization of releases of flammable substances
To reduce the risk of explosions caused by flammable substance leaks, it is essential that equipment, protective systems, and components are designed, constructed, and operated to remain leak-free However, small leaks can occur, particularly at pump glands and sampling points, which must be considered during the design process Measures should be implemented to minimize leak rates and prevent the spread of flammable substances, and leak detectors should be installed where necessary.
Effective ventilation is crucial for managing the impact of flammable gas and vapor releases It plays a vital role in both internal and external environments, including equipment, protective systems, and components.
For dusts, ventilation generally provides sufficient protection only when the dust is extracted from the place of origin (local extraction) and hazardous deposits of combustible dust are reliably prevented.
Classification of hazardous atmospheric conditions
General
Mines face significant risks from both firedamp and combustible dust simultaneously, making it unwise to separate the hazards associated with gas and dust atmospheres Consequently, explosion prevention and protection measures must address the dangers posed by both firedamp and combustible dust.
Mining operations are conducted well beyond the explosion range of underground firedamp and dust to prevent catastrophic incidents In Europe, it is standard practice to implement a safety factor, which includes de-energizing equipment and evacuating miners when atmospheric conditions reach a certain percentage of the lower explosion limit (LEL) as stipulated by national regulations.
NOTE 1 It is ensured by the layout and management of the mine, the rating of the ventilation, the firedamp drainage ventilation etc that during normal operation the limits (permissible concentration) laid down in the respective national legislation are not exceeded
Under abnormal conditions, the concentration of firedamp in underground ventilation air may temporarily exceed safe limits This creates a potentially explosive atmosphere that, if not properly ventilated, can pose a significant risk to extensive areas of the mine along the exhaust air path.
NOTE 2 Mine workings where a hazardous explosive atmosphere is not likely to occur are classified as not dangerous These include in general the intake air shafts and continuously ventilated workings in the area around the pit bottom of these shafts They can also include workings where there is evidence that a concentration of methane specified by national legislation is not exceeded However, influences of mining on these workings can still introduce hazards
In determining hazardous situations in mines, the word “zone” is intentionally not used as this notion is used for a space of specific dimensions around a technical plant.
Hazardous atmospheric conditions
The hazardous atmospheric conditions are classified as follows:
Explosive atmosphere: underground parts of mines and associated surface installations of such mines endangered by firedamp and/or combustible dusts
NOTE 1 This includes mine workings where the concentration of firedamp is within the explosion range e.g as a result of malfunction (e.g breakdown of fans), sudden release of large amounts of firedamp (gas outburst) or increased gas emission (due to decrease of air pressure or increased coal winning)
Potentially explosive atmosphere: underground parts of mines and associated surface installations of such mines likely to be endangered by firedamp and/or combustible dusts
NOTE 2 This includes mine workings where the concentration of firedamp in the ventilating current or in the firedamp drainage system is outside the explosion range.
Requirements for the design and construction of equipment, protective systems and
General
In mines where firedamp may include substantial amounts of flammable gases beyond methane, it is essential that equipment, protective systems, and components are designed and constructed to meet the standards for both group I and group II gases.
In hazardous conditions, it is essential to assess the potential for ignition hazards by referencing the ignition processes outlined in Clause 5 of EN 1127-1:2011 If ignition hazards are identified, it is crucial to eliminate the sources of ignition When removal is not feasible, protective measures specified in sections 6.4.1 to 6.4.14 must be implemented, ensuring careful consideration of all relevant factors.
To minimize the risk of ignition sources, it is essential to implement measures that either neutralize these sources or decrease their likelihood of occurrence This can be accomplished through the careful design and construction of equipment, protective systems, and components, as well as by establishing effective operational procedures and utilizing suitable measuring and control systems.
NOTE 1 This will also be achieved by using only equipment, protective systems and components intended for monitoring, averting, reducing or fighting explosion hazards/damages or for warning, self-aid or rescuing endangered persons in cases where the firedamp concentration is above the permissible limit
NOTE 2 Directive 94/9/EC specifies different categories of equipment which reflect the requirements of the different atmospheric conditions
The criteria determining the classification into categories are the following:
Category M 1 includes equipment that is specifically designed and, when required, equipped with additional protective features to operate according to the manufacturer's established parameters, ensuring a high level of safety and reliability.
Equipment in this category is designed for use in underground mining areas and surface installations that are at risk of firedamp and combustible dust.
Equipment in this category shall remain functional even in the event of rare equipment faults in an explosive
— in the event of failure of one means of protection, at least an independent second means provides the requisite level of protection;
— or the requisite level of protection is ensured in the event of two faults occurring independently of each other
Category M 2 comprises equipment designed to be capable of functioning in conformity with the operational parameters established by the manufacturer and ensuring a high level of protection
Equipment in this category is designed for underground mining operations and surface installations that may be at risk from firedamp and combustible dust.
This equipment is intended to be de-energized in the event of an explosive atmosphere
Equipment in this category is designed to provide essential protection during normal operations and under harsher conditions, such as rough handling and fluctuating environmental factors The standards for explosion protection and prevention, including the construction and marking of equipment and components, are outlined in EN 1710.
The relation between categories and atmospheric conditions is illustrated in Annex A
Depending on the category, the following general requirements for equipment, protective systems and components shall be complied with:
Category M 2: Sources of ignition shall not become effective during normal operation - even in the event of severe operating conditions and especially in rough operation and changing environmental conditions
Category M 1: In addition to the avoidance of sources of ignition specified for category M 2, sources of ignition that can occur in rare incidents only shall be avoided
All categories: If the explosive atmosphere contains several types of flammable gases or dusts, the protective measures shall generally be based on the results of special investigations
To ensure safety, it is crucial to identify and effectively avoid all types of ignition sources, as relying solely on this measure is insufficient The specific guidelines for avoiding various ignition sources under different atmospheric conditions are detailed in sections 6.4.2 to 6.4.14.
Hot surfaces
For the identification of hazards due to hot surfaces, see 5.1
When hazards from hot surfaces are recognized, the equipment, protective systems, and components must comply with specific requirements based on the type of explosive atmosphere, such as firedamp and/or combustible dust, and its category.
Category M 1: The temperatures of all equipment, protective system and component surfaces which can come into contact with explosive atmospheres shall not - even in the case of rare malfunctions - exceed:
— 80 % of the minimum ignition temperature of the firedamp, in degrees Celsius and/or
NOTE 1 This is usually measured as the maximum surface temperature of 450 °C for Group I equipment
— 2/3 of the minimum ignition temperature of the dust/air mixture concerned, in degrees Celsius
Moreover, the temperature of surfaces on which dust can be deposited shall not exceed 150 °C; this shall be ensured even in the case of rare malfunctions
In Category M 2, it is essential that the temperatures of all equipment, protective systems, and component surfaces that may encounter explosive atmospheres during normal operation, including under severe and fluctuating environmental conditions, do not exceed specified limits.
— 80 % of the ignition temperature of the firedamp, in degrees Celsius and/or
NOTE 2 This is usually measured as the maximum surface temperature of 450 °C for Group I equipment
— 2/3 of the minimum ignition temperature of the dust/air mixture concerned, in degrees Celsius
Moreover, the temperature of surfaces on which dust can be deposited shall not exceed 150 °C
NOTE 3 For reciprocating internal combustion engines, see EN 1834–2.
Flames and hot gases
For identifying hazards related to flames and hot gases, refer to section 5.2 of EN 1127-1:2011 Additionally, for concerns regarding hot solid particles, such as flying sparks, consult section 6.4.4 on mechanically generated sparks and section 6.5.1 regarding flame propagation.
If hazards due to flames and/or hot gases have been identified, depending on the category, the equipment, protective systems and components shall meet the following requirements:
Category M 2: Naked flames for operational and other intended purposes are not permitted
In addition to naked flames, the use of gases from flames, such as for inerting purposes, or other heated gases is allowed, provided that special preventive measures are implemented These measures may include restricting temperature or eliminating explosive particles This regulation is applicable during normal operations, even under severe conditions, particularly in challenging environments with fluctuating conditions.
Category M 1: The requirements for category M 2 shall be met even in the case of rare malfunctions.
Mechanically generated sparks
For the identification of hazards due to mechanically generated sparks, see 5.3
Frictional sparks from cutting tools in mining operations can ignite gas or dust atmospheres, but this risk can be significantly mitigated by implementing effective water spray systems or using specially designed cutting tools When ignition hazards are present, a water spray system should be installed around the cutting head to extinguish sparks, reduce airborne dust, and provide fresh air to dilute any gases released during the cutting process It is essential that these water spray systems are monitored and integrated with machine controls to ensure that cutting operations cannot proceed without the proper functioning of the water sprays.
When hazards from mechanically generated sparks are identified, the equipment, protective systems, and components must comply with specific requirements based on the type of explosive atmosphere, such as firedamp or combustible dust, and its category.
Category M 1: Equipment, protective systems and components which, even in the case of rare malfunctions, can generate explosive friction, impact or abrasion sparks are not permitted
Category M 2 includes equipment, protective systems, and components that can produce explosive sparks from friction, impact, or abrasion during normal and severe operating conditions To ensure safety, these items must be equipped with adequate protective measures to prevent any ignition sources from becoming active.
The use of light metals, such as aluminum, magnesium, titanium, and zirconium, for exposed surfaces of equipment and protective systems is allowed only if the total content of these metals does not exceed 15%, with a specific limit of 7.5% for magnesium, titanium, and zirconium combined.
The requirements for tools for use in potentially explosive atmospheres shall be in accordance with Annex B
Coating light metals with non-conductive materials like plastics can effectively protect them from rust due to mechanical contact However, it is essential to take precautions against static electricity when using such coatings Additionally, the coating should have low aluminum content to ensure optimal performance.
To minimize the risk of ignition from mechanically generated sparks, wetting can be an effective strategy However, it is essential to consider potential reactions with the wetting medium, such as the production of hydrogen when using water with light metals.
Analyses of industrial events and investigation results indicate that there is no risk of ignition of dust/air mixtures caused by mechanically generated sparks when circumferential velocities are low (≤ 1 m/s).
Electrical equipment
For the identification of hazards arising from electrical equipment, see 5.4
Electrical equipment shall be designed, constructed, installed and maintained in accordance with the relevant European Standards.
Stray electric currents
For the identification of hazards arising from stray electric currents, see 5.5
To mitigate hazards from stray electric currents, it is essential to ensure that all external conductive parts of the equipment, along with protective systems and components, are connected through equipotential bonding using conductors with sufficient current carrying capacity Additionally, where feasible, these components should be bonded to earth to prevent the occurrence of explosive arcs or temperature increases caused by stray electric currents.
Static electricity
For the identification of hazards due to static electricity, see 5.6 of EN 1127-1:2011
If hazards due to static electricity have been identified, the requirements of EN 13463-1:2009, 6.7 and of
EN 60079-0 apply This information shall be included in the information for use (see Clause 7)
NOTE For further information on this subject, see Technical Report CLC/TR 50404.
Lightning
For the identification of hazards due to lightning, see 5.7 of EN 1127-1:2011
To mitigate lightning hazards, it is essential to implement above-ground measures that prevent lightning strikes from affecting underground operations This can be achieved by using surge diverters to isolate surface electrical circuits from those underground, ensuring that interconnecting equipment like pipes and electric cables do not transmit lightning strikes.
Radio frequency (RF) electromagnetic waves from 104 Hz to 3 × 1011 Hz
For the identification of hazards due to radio-frequency electromagnetic waves, see 5.8 of EN 1127-1:2011
To ensure safety in potentially explosive atmospheres, it is essential to maintain a safety distance in all directions between the nearest radiating components and the receiving aerial, as outlined in section 6.4.9 of EN 1127-1:2011, when hazards from radio frequency electromagnetic waves are identified.
NOTE 1 For transmission systems with a directional pattern, it is worth noting that this safety distance depends on the direction
If an adequate safety distance cannot be maintained, other protective measures shall be taken, for example limiting the power output of the transmitter or shielding
NOTE 2 Operating permits on the level of electromagnetic interference, issued by the national Telecom Authority for example, the respective radio interference protection label or information on the degree of radio interference do not contain any information about whether the device or its radiation field is an ignition risk
NOTE 3 The wireless intercommunication systems commonly used in mining generally do not produce such hazards as the power output is usually so limited that arcs cannot be struck
NOTE 4 See EN 50303 for further guidance on RF transmitters of category M 1 This standard specifies a maximum power output of 6 W for the prevention of ignition of the atmosphere by RF transmitters
RF equipment and systems for use in potentially explosive atmospheres shall also comply with 6.4.5.
Electromagnetic waves from 3 × 1011 Hz to 3 × 1015 Hz
For the identification of hazards arising from this spectral range of electromagnetic waves, see 5.9 of
Note shall be taken that equipment, protective systems and components that generate radiation (e.g lamps, electric arcs, lasers) can also be a source of ignition as defined in 6.4.2 and 6.4.5
If hazards due to electromagnetic waves from 3 × 1011 Hz to 3 × 1015 Hz have been identified, depending on the category, the equipment, protective systems and components shall meet the following requirements:
All categories: Devices which can cause ignition by resonance absorption (see 5.9 of EN 1127-1:2011) are not permitted
Category M 2 permits electrical equipment that generates radiation under specific conditions: a) the energy of a radiated pulse or the power of continuous radiation must be kept at a low level to prevent ignition of the explosive atmosphere; or b) the radiation must be safely contained within an enclosure.
1) any escape of radiation from the enclosure into the hazardous area that could ignite the explosive atmosphere is safely prevented and hot surfaces that could ignite the explosive atmosphere on the outside of the enclosure do not occur due to the radiation, and
2) the explosive atmosphere cannot penetrate into the enclosure or an explosion inside the enclosure cannot propagate into the potentially explosive atmosphere
This shall be ensured during normal operation and also in the case of more severe operating conditions
Category M 1 requires that, in addition to the criteria for category M 2, the equipment must be designed and constructed to ensure that sources of ignition remain ineffective, even in the case of rare malfunctions.
EN 50303 with regard to the power level and flux density permitted for optical laser transmission equipment)
Ionizing radiation
For the identification of hazards arising from ionizing radiation, see 5.10 of EN 1127-1:2011
If hazards due to ionizing radiation have been identified, the requirements of 6.4.5 shall be met for the electrical systems needed for operation of the sources of radiation
Electrical equipment that produces ionizing radiation is allowed, as long as the energy of the emitted pulse or the power of continuous radiation is kept at a sufficiently low level to prevent ignition of an explosive atmosphere.
Ultrasonics
For the identification of hazards arising from ultrasonics, see 5.11 of EN 1127-1:2011
Ultrasonic waves exceeding a frequency of 10 MHz are prohibited if hazards have been identified, unless it can be demonstrated that there is no risk of ignition by proving the absence of absorption due to molecular resonance.
Ultrasonic waves can be utilized only when the safety of the work process is guaranteed The generated acoustic field's power density must not exceed 1 mW/mm², unless it is demonstrated that ignition is not a risk in the specific situation.
Adiabatic compression and shock waves
For the identification of hazards due to adiabatic compression and shock waves, see 5.12 of EN 1127-1:2011
If hazards due to adiabatic compression and/or shock waves have been identified, depending on the category, the equipment, protective systems and components shall meet the following requirements:
To prevent ignition, it is essential to avoid processes that may lead to compressions or shock waves, even during rare malfunctions Hazardous compressions and shock waves can typically be mitigated by ensuring that valves between sections of the system with high pressure ratios are opened slowly.
Category M 2: Processes which can cause adiabatic compressions or shock waves during normal operation that could ignite explosive atmospheres shall be avoided
If equipment, protective systems and components containing highly oxidizing gases are used, special precautions should be taken to prevent the ignition of materials and auxiliary materials.
Exothermic reactions, including self-ignition of dusts
For the identification of hazards due to exothermic reactions, see 5.13
To mitigate hazards from exothermic reactions, it is essential to avoid substances prone to self-ignition whenever feasible When handling such materials, it is crucial to establish appropriate protective measures tailored to each specific situation.
To mitigate the risk of self-ignition in underground minerals and substances, it is essential to implement effective prevention measures These may include the removal of hazardous materials, chemical control of reactions, the use of isolated ventilation or enclosures, and minimizing air leakages from old workings.
Requirements for design and construction of equipment, protective systems and
General
If the measures outlined in sections 6.2 or 6.4 are impractical or inadvisable, the design and construction of equipment, protective systems, and components must focus on minimizing the impact of an explosion to a safe level through various effective strategies.
— explosion-resistant design according to EN 14460;
— explosion relief according to EN 14797;
— explosion suppression according to EN 14373;
— prevention of flame and explosion propagation according to EN 15089
These measures generally relate to the limitation of hazardous effects of explosions inside equipment, protective systems and components
NOTE Additional requirements can be necessary for buildings or surroundings of equipment, protective systems and components, but these are not dealt with in this European Standard
In connected systems, the risk of explosion propagation is significant, as flame front acceleration can occur through protective systems, components, and pipeworks Elements that increase turbulence, such as measuring baffle plates, may further accelerate the flame front This acceleration, influenced by the system's geometry, can result in a dangerous transition from deflagration to detonation, leading to high-pressure pulses.
In underground mining, it is essential to consider not only the interior of equipment and safety systems but also the interactions between these facilities and any hazardous explosive atmospheres present in the surrounding mine workings.
Many measures outlined in European Standards are applicable to surface mining installations; however, their use is limited in specific underground mining designs Consequently, the primary focus for explosion prevention and protection in underground mining should be on eliminating ignition sources.
Special equipment for underground mining
Explosion suppression systems, such as automatic explosion extinguishing installations, are designed to include an automatic flame detection system, a trigger unit, and an extinguishing unit equipped with a reservoir of extinguishing agents and nozzles These systems ensure that the extinguishing agent is quickly injected into the area of an incipient explosion and distributed as uniformly as possible.
Explosion barriers must be engineered to stop the spread of explosion fronts to adjacent galleries or other underground operations, ensuring effectiveness across the entire cross-section of the relevant underground workings.
Explosion-proof ventilation systems, such as air doors and closing devices for passageways, must be designed to endure the pressure surge from an explosion without losing functionality These systems are essential for ensuring that personnel can safely escape and that rescue operations can proceed effectively, while also minimizing the impact of explosions.
Provisions for emergency measures
Special emergency measures may be required for explosion prevention and/or protection, e.g
— emergency shut-down of the total mine or parts of it;
— emergency emptying of parts of the mine;
— interrupting material flows between parts of the mine;
— flooding of parts of the mine by appropriate substances (e.g nitrogen, water)
These measures shall be integrated into the explosion safety concept (see 6.1) during the design and construction of the equipment, protective systems and components.
Principles for measuring and control systems for explosion prevention and protection
General principles of this field are dealt with in EN ISO 13849-1
The explosion prevention and protection measures outlined in sections 6.2, 6.4, and 6.5 can be effectively implemented or monitored through measuring and control systems, enabling process control to adhere to three key safety principles.
— avoidance of effective ignition sources;
The relevant safety parameters shall be identified and monitored Measuring and control systems used shall produce the appropriate response
NOTE The response time of the measuring and control systems is also a relevant safety parameter
The required reliability of the monitoring and control system (see EN 50495 and EN 13463-6) follows from the risk assessment (see EN 15198 and EN 13463-1)
General
This clause outlines the necessary information for the use and maintenance of the equipment, protective systems, and components, which will be provided as part of the user instructions, such as an instruction handbook.
The requirements of EN ISO 12100 shall be met Particular attention shall be given to the special requirements for use in explosive atmospheres
The information for use shall clearly state the equipment group and the category, if applicable and include especially the intended use and the application limits
The following information shall be provided, as appropriate: a) specific parameters related to explosion protection; this can include:
1) maximum surface temperatures, pressures etc.;
4) prevention and/or limitation of dust accumulation b) safety systems; this can include:
3) spark detection and extinguishing systems;
8) vent systems for overpressures generated from processes other than explosion;
9) fire detection and fighting systems;
12) explosion-resistant design c) specific requirements to ensure safe operation; this can include:
2) use with other equipment, protective systems and components
Annex B provides information for the use of tools in potentially explosive atmospheres.
Information for commissioning, maintenance and repair to prevent explosion
It is essential to include detailed instructions for normal operations, such as start-up and shut-down procedures, as well as guidelines for systematic maintenance and repair This should encompass safe equipment opening practices and necessary protective measures.
The article emphasizes the importance of providing clear instructions for cleaning procedures, including dust removal and safe working practices It also highlights the necessity of guidelines for fault identification and the required actions to address them Additionally, it outlines the need for testing protocols for equipment, safety systems, and components following explosions Furthermore, it stresses the importance of communicating risks, particularly regarding the potential presence of explosive atmospheres identified in risk assessments, to prevent operators and others from becoming ignition sources.
Qualifications and training
The manufacturer must provide details on the necessary qualifications and training, enabling the mine owner to choose skilled and experienced personnel for specialized tasks related to equipment, protective systems, and components utilized in potentially explosive environments.
Relation between categories and hazardous atmospheric conditions
The relation between categories of equipment, protective systems and components and atmospheric conditions in which they are to be used is shown in Table A.1:
Table A.1 — Relation between categories and hazardous atmospheric conditions
Category Designed for atmospheric condition Also applicable in atmospheric condition
M 1 Firedamp and/or combustible dusts Explosive atmosphere Potentially explosive atmosphere
M 2 Firedamp and/or combustible dusts Potentially explosive atmosphere -
Tools for use in potentially explosive atmospheres
When using hand-held tools, it is essential to differentiate between two categories: a) tools that produce a single spark during operation, such as screwdrivers, spanners, and impact screwdrivers; and b) tools that create a shower of sparks, particularly during separating or grinding tasks.
In explosive atmosphere, no tools shall be used which can cause sparks
In potentially explosive atmosphere, only steel tools in accordance with a) are permissible
Tools in accordance with b) are only permissible, if it is ensured that
1) no hazardous explosive atmosphere is present at the workplace and
2) dust deposits have been removed from the workplace or
3) the workplace is kept so wet that no dust can be dispersed in the air and no smoulder spots can develop
In grinding or separating operations, sparks can travel significant distances and create smoldering particles, necessitating the implementation of protective measures in surrounding areas of the workplace.
Significant technical changes between this document and the previous edition of this European Standard
The significant changes with respect to EN 1127-2:2002+A1:2008 are listed below:
Table C.1 — Significant technical changes between this document and EN 1127–2:2002+A1:2008
Type Minor and editorial changes
Terms and definitions have been moved to EN 13237 3 X
Risk assessment has been modified 4 X
Terms “hazardous condition 1” and “hazardous condition 2” have been deleted Introduction,
Adaption to EN 1127–1:2011 the whole standard X
Minor and editorial changes involve modifications to a previous standard that are either editorial or of a minor technical nature These changes include clarifying technical requirements through wording adjustments without altering the technical content, as well as reducing the level of existing requirements.
Extension: addition of technical options
Changes classified as 'extension' in a standard involve modifications that introduce new technical requirements or options while ensuring that existing compliant equipment is not subjected to increased demands Consequently, products adhering to the previous edition will not need to account for these extensions.
Major technical changes: addition of technical requirements increase of technical requirements
Major technical changes in a standard involve modifications that introduce new technical requirements or elevate existing ones As a result, products compliant with the previous standard may no longer meet the updated criteria.
Products must adhere to 'Major Technical Changes' in line with the previous edition This annex offers further details on each change categorized as a 'Major Technical Change'.
NOTE These changes represent current technological knowledge However, these changes will not normally have an influence on equipment already placed on the market
Relationship between this European Standard and the Essential
Requirements of EU Directive 94/9/EC
This European Standard was developed under a mandate from the European Commission and the European Free Trade Association to ensure compliance with the Essential Requirements of the New Approach Directive 94/9/EC, dated 23 March 1994, which pertains to equipment and protective systems designed for use in potentially explosive atmospheres.
Citing this standard in the Official Journal of the European Union and implementing it as a national standard in at least one Member State grants a presumption of conformity with the Essential Requirements of the Directive and related EFTA regulations, as outlined in Table ZA.1, within the standard's scope.
Table ZA.1 — Correspondence between this European Standard and Directive 94/9/EC
Clause(s)/sub-clause(s) of this
EN Essential Requirements (ERs) of Directive 94/9/EC Qualifying remarks/Notes
Annex II, with the exception of the following clauses:
1.0.5 Marking 1.2.6 Safe opening 1.2.7 Protection against other hazards
1.2.8 Overloading of equipment 1.4 Hazards arising from external effects
1.5 Requirements in respect of safety-related devices 1.6 Integration of safety requirements relating to the system
2.1 Requirements applicable to equipment in category
2.2 Requirements for category 2 of equipment- group II
2.3 Requirements applicable to equipment in category
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard
Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC
This European Standard was developed under a mandate from the European Commission and the European Free Trade Association to ensure compliance with the Essential Requirements of the New Approach Directive 2006/42/EC, which pertains to machinery regulations established by the European Parliament and Council on May 17, 2006.
Once the standard is published in the Official Journal of the European Union and adopted as a national standard by at least one Member State, adherence to the clauses outlined in Table ZA.1 provides a presumption of conformity with Essential Requirement 1.5.7 of the Directive and related EFTA regulations, within the standard's scope.
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard
[1] Council Directive 89/686/EEC of 21 December 1989 on the approximation of the laws of the Member States relating to personal protective equipment
Directive 94/9/EC, established by the European Parliament and Council on March 23, 1994, aims to harmonize the laws of Member States regarding equipment and protective systems designed for use in potentially explosive atmospheres.
The ATEX Guidelines outline the application of Directive 94/9/EC, established by the European Parliament and Council on March 23, 1994 This directive focuses on harmonizing the laws of Member States regarding equipment and protective systems designed for use in potentially explosive atmospheres.
[4] Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery CLC/TR 50404, Electrostatics — Code of practice for the avoidance of hazards due to static electricity
CLC/TR 50426, Assessment of inadvertent initiation of bridge wire electro-explosive devices by radio- frequency radiation — Guide
CLC/TR 50427, Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation — Guide
EN 1834-2 outlines the safety requirements for the design and construction of reciprocating internal combustion engines intended for use in potentially explosive atmospheres This standard specifically addresses Group I engines that are utilized in underground environments prone to firedamp and combustible dust Compliance with these safety regulations is crucial to ensure the safe operation of engines in hazardous conditions.
EN 13463-2, Non-electrical equipment for use in potentially explosive atmospheres - Part 2: Protection by flow restricting enclosure 'fr'
EN 13463-3, Non-electrical equipment for use in potentially explosive atmospheres - Part 3: Protection by flameproof enclosure 'd'
EN 13463-5, Non-electrical equipment intended for use in potentially explosive atmospheres - Part 5:
EN 13463-8, Non-electrical equipment for potentially explosive atmospheres - Part 8: Protection by liquid immersion 'k'
EN 14591-1, Explosion prevention and protection in underground mines - Protective systems - Part 1:
2-bar explosion proof ventilation structure
EN 14591-2, Explosion prevention and protection in underground mines - Protective systems - Part 2:
EN 14591-4, Explosion prevention and protection in underground mines - Protective systems - Part 4:
Automatic extinguishing systems for road headers
EN 14983, Explosion prevention and protection in underground mines - Equipment and protective systems for firedamp drainage
EN 14986, Design of fans working in potentially explosive atmospheres
EN 15188, Determination of the spontaneous ignition behaviour of dust accumulations
EN 15198, Methodology for the risk assessment of non-electrical equipment and components for intended use in potentially explosive atmospheres
EN 15233, Methodology for functional safety assessment of protective systems for potentially explosive atmospheres
EN 50303, Group I, category M 1 equipment intended to remain functional in atmospheres endangered by firedamp and/or coal dust
EN 50495, Safety devices required for the safe functioning of equipment with respect to explosion risks
EN 60079-1, Explosive atmospheres — Part 1: Equipment protection by flameproof enclosures “d"
EN 60079-5, Explosive atmospheres — Part 5: Equipment protection by powder filling “q"
EN 60079-6, Explosive atmospheres — Part 6: Equipment protection by oil immersion “o"
EN 60079-7, Explosive atmospheres — Part 7: Equipment protection by increased safety “e"
EN 60079-11, Explosive atmospheres — Part 11: Equipment protection by intrinsic safety “i"
EN 60079-18, Electrical apparatus for explosive gas atmospheres — Part 18: Construction, test and marking of type of protection encapsulation “m” electrical apparatus
EN 60079-20-1, Explosive atmospheres — Part 20-1: Material characteristics for gas and vapour classification — Test methods and data
EN 60079-25, Electrical apparatus for explosive gas atmospheres — Part 25: Intrinsically safe systems
EN 60079-26, Explosive atmospheres — Part 26: Equipment with equipment protection level (EPL) Ga
EN 60079-28, Explosive atmospheres — Part 28: Protection of equipment and transmission systems using optical radiation
EN 60079-29-1, Explosive atmospheres — Part 29-1: Gas detectors — Performance requirements of detectors for flammable gases
EN 60079-29-2 Explosive atmospheres — Part 29-2: Gas detectors — Selection, installation, use and maintenance of detectors for flammable gases and oxygen
EN 60079-30-1, Explosive atmospheres — Part 30-1: Electrical resistance trace heating — General and testing requirements
EN 60079-30-2, Explosive atmospheres — Part 30-2: Electrical resistance trace heating — Application guide for design, installation and maintenance
EN 60079-31, Explosive atmospheres — Part 31: Equipment dust ignition protection by enclosure “t"
EN 60079-35-1, Explosive atmospheres — Part 35-1: Caplights for use in mines susceptible to firedamp — General requirements - Construction and testing in relation to the risk of explosion
EN 60079-35-2, Explosive atmospheres — Part 35-2: Caplights for use in mines susceptible to
EN 61340-4-4, Electrostatics — Part 4-4: Standard test methods for specific applications —
Electrostatic classification of flexible intermediate bulk containers (FIBC)
EN 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-related systems
EN 62305-2, Protection against lightning — Part 2: Risk management
EN 62305-3, Protection against lightning — Part 3: Physical damage to structure and life hazard
The EN ISO/IEC 80079-34 standard outlines the application of quality systems for the manufacture of equipment used in explosive atmospheres, ensuring safety and compliance in hazardous environments Additionally, the prEN ISO IEC 80079-38 standard focuses on the requirements for equipment and components specifically designed for use in explosive atmospheres found in underground mines, emphasizing the importance of safety measures in these critical settings.
IEC 60050-426, International Electrotechnical Vocabulary — Part 426: Equipment for explosive atmospheres