Statutory regulations and standards

Introduction

Areas in which there is a risk of explosion that may harm people or the environment are subject to legal or comparable rules in most countries of the world. While these rules were initially issued at the national level, they have since been replaced over the last years by regional European directives and standards, and in the field of standardization they have partially been replaced by international regulations.

European Directives

Already in 1976, the Council of the European Community established the prerequisite of free trade of explosion protected electrical equipment within the European Union by ratifying the “Directive on the harmonization of the laws of the member states concerning electrical equipment for use in potentially explosive atmospheres (76/117/EEC)”. This directive has since always been adapted to the state of the art by means of individual and additional guidelines. These have, however, applied only to electrical equipment.

Complete harmonization and extension to all types of equipment was achieved with the new Directive 94/9/EC in 1994. Directive 99/92/EC, which regulates operation in potentially explosive areas and defines safety measures for the concerned personnel, was issued in 1999.

EC Directive 94/9/EC (ATEX 95)

EC Directive 94/9/EC “on the alignment of the laws of the Member States concerning devices and protection systems intended for use in potentially explosive atmospheres" was issued in 1994 to further standardize explosion protection and make corresponding adjustments in line with a new directive approach. It specifies the requirements for explosion protected devices and protection systems by prescribing essential health and safety requirements. It guarantees free trade within the European Union, as agreed in Article 95 (former 100 a) of the treaty established between the European Community member states. This is also the source of the term generally used amongst experts, ATEX 95 or 100 a, which is the abbreviation of the French designation for explosive atmospheres, “atmosphères explosibles”.

The directive had to be implemented into national law without any changes/exceptions. E.g., it was adopted into British law by means of The Equipment and Protective Systems for Use in Potentially Explosive Atmospheres Regulations (EPS) and into German law by means of the “Explosionsschutzverordnung (ExVO)” (Regulation of Explosion Protection) as the 11th Regulation of the “Geräte- und Produktsicherkeitsgesetz (GPSG)” (Equipment and Product Safety Law).

The directive applies to all industrial potentially explosive areas including mining, and also covers dust explosion protection. The scope covers all electrical and non-electrical equipment, and protection systems.

This directive is intended for the manufacturer or the importer, and defines design, certification, production and quality assurance, marking, operating instructions, and declaration of conformity for the explosion protected equipment to be placed on the market.

Definitions

  • “Equipment” means machines, apparatus, fixed or mobile devices, control components and instrumentation thereof, and warning or 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 which are capable of causing an explosion through their own potential sources of ignition.
  • "Protection systems" refer to all equipment that is intended to halt incipient explosions immediately and/or to limit the effective range of an explosion and which is to be placed on the market for use as autonomous systems.
  • "Components" refer to any item essential to the safe operation of equipment and protection systems but with no autonomous function of its own.
  • An "explosive atmosphere" is a mixture of air and flammable substances in the form of gases, vapors, mists, or dusts at atmospheric conditions in which, after ignition has occurred, combustion spreads to the entire unburned mixture.
  • A "potentially explosive atmosphere" is an area in which the atmosphere could become explosive due to local and operational conditions.

Area of application

The directive applies to equipment and protective systems for use in potentially explosive areas.

Safety, inspection and control devices intended for use outside potentially explosive atmospheres but required for or contributing to the safe functioning of equipment with respect to the risk of explosion are also covered by the scope of this directive. The directive does not include a reference to mandatory standards, whereas it specifies the essential health and safety requirements to be maintained, and which are mandatory for design and construction. Protection against other hazards (e.g., electric shock) that could be caused by this equipment, is required as well.

Equipment categories

The manufacturer of equipment that includes their own potential ignition sources, and therefore can cause an explosion, must ensure that the equipment undergoes an ignition hazard assessment procedure, and take measures according to the essential safety requirements to exclude the risk of ignition. In the directive, group II apparatus are divided into three categories with various levels of safety (for mines group I has two categories). The required protective measures suit the required level of safety.

Categories of group I: surface and underground mining systems in case of dangerous firedamp/dust:

Category M1Category M2
Very high degree of safetyHigh degree of safety
Safe even when two faults occur independentlySwitch-off in case of the presence of explosive atmosphere

Categories of group II: other explosive areas:

Category 1Category 2Category 3
Very high degree of safetyHigh degree of safetyNormal degree of safety
Safe even when two faults occur independentlySafe even when a fault occursSafe during normal operation

Certification

Equipment for use in hazardous areas has to undergo the conformity assessment procedure defined in the directive prior to being placed on the market. Category 1 and M1 equipment must undergo an EC type examination carried out by a notified inspection authority. The same applies to electrical equipment and I.C.-engines of category 2 and M2. For other non-electrical equipment of this category, as well as for that of category 3, the manufacturer is authorized to assess and document conformity with the requirements of the directive.

The certificates from a notified European inspection authority are recognized throughout the EU.

Certification

In addition to the usual data such as the name of the manufacturer, type, serial number, and electrical ratings, any data relating to explosion protection must be contained in the marking (see table 5, Marking according to Directive 94/9/EC and the standards EN 60079 ff and EN 61241 ff).

The CE marking of the equipment confirms that it is designed and manufactured in compliance with all applicable EU Directives. For example, an explosion protected optical sensor marked with the CE conformity mark must comply with both the explosion protection directive as well as the “EMC Directive”.

Operating instructions

The operating instructions of the manufacturer must clearly define the intended use of the equipment by the operator. The minimum requirements for the operating instruction are, among others:

Information on safe

  • commissioning
  • use
  • mounting and dismounting
  • servicing (maintenance and troubleshooting)
  • rigging
If necessary, special conditions for safe use have to be specified and should include notes on possible misuse that may occur as experience has shown.

Manufacturer’s declaration of conformity

Equipment and systems can be placed on the market only if marked with the CE mark and complete with operating instructions and the manufacturer’s declaration of conformity. The CE conformity marking and the written declaration of conformity confirm that the product complies with all requirements and assessment procedures specified in the EC Directives.

Marking of electrical equipment:

Marking defined by directives and standards
Manufacturer’s name or designation
Leuze electronic
Type designation (e.g.)* 92/3 * Ex
⇒ Explosion protection marking¹(E) Ex ia IIC T6
(E) Ex ia D21 T80°C
⇒ Marking according to CENELECEEx or Ex (from 12/2004)
⇒ Protection typesia
⇒ Explosion groups for gasesII
⇒ Temperature class or in case of dust the max. surface temperature of apparatusT6; T80°C
Marking acc. to Directive 94/9/EC
II 2 G D
⇒ EU distinguishing mark
⇒ Equipment groupII
⇒ Equipment category1, 2 or 3
⇒ G: gases, vapors or mists; D: dustsG, D
Testing authority, number of certificateDMT 03 ATEX E 029
CE mark, number of the auditing and supervising authority
0158
Electrical dataV, A, W, Hz
Ambient temperature,
of other than –20°C…+40°C
Ta ≤ +50 °C
¹ With an ... X if reference is made to special conditions for use, etc.

EC Directive 99/92/EC

In addition to Directive 94/9/EC, which regulates how explosion protected equipment and protection systems are placed on the market and the design, construction and quality requirements to be met by them, Directive 99/92/EC "Minimum requirements for improving the health and safety protection of worker potentially at risk from explosive atmospheres," refers to the operation of potentially explosive installations, and is therefore intended for the employer. This directive contains only minimum requirements. When implementing it into national law, the single states can adopt further regulations. This was done when implementing it into British law by “The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR)” and into German law by the “Betriebssicherheitsverordnung (BetrSichV)”, the German regulation on Industrial Safety and Health Protection, which in addition to this directive, takes into consideration further European directives on safety on work. The Betriebssicherheitsverordnung "Ordinance governing the health and safety aspects of the provision and use of materials at work, the operation of equipment requiring supervision and the organization of occupational health and safety precautions" contains, e.g., detailed regulations on the operation of Ex-systems, particularly on the monitoring, inspection and maintenance of these systems. Comparable regulations are found in other European countries.

According to Directive 99/92/EC, it is the duty of the employer to verify where there is a risk of explosion, classify the hazardous areas into zones accordingly, and document all measures taken to protect the personnel in the explosion protection document.

Assessment of explosion risks

When assessing the risks of explosion, the following factors are to be taken into account:

  • The probability and duration of the occurrence of a dangerous potentially explosive atmosphere
  • The probability of the presence and activation of ignition sources and of their becoming effective
  • The used substances, processes, and their possible interactions
  • The extent of the anticipated effects of explosions

Zone classification

The owner is to classify the areas in which explosive atmospheres may be present into zones and to ensure that the minimum organizational and technical requirements of the directive are observed.

Zone 0

An area in which a explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor or mist is present continuously or for long periods or frequently.

Zone 1

An area in which an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor or mist is likely to occur in.

Zone 2

An area in which an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Zone 20

An area in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently.

Zone 21

An area in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.

Zone 22

An area in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

The table contains an overview of the zones and assignment of equipment according to category.

Zones and allocation of equipment according to category:

ZoneDuration of the occurrence of an explosive atmosphereEquipment category

Gases, vapors,
mists
0continuously, for a long period, frequently1G
1occasionally2G
2rarely3G
Dusts20continuously, for a long period, frequently1D
21occasionally2D
22rarely3D

Explosion protection document

An explosion protection document has to be generated which contains at least the following information:

  • Assessment of the explosion risk
  • Protective measures taken
  • Zone classification
  • Observance of minimum requirements. These are divided into organizational measures (instruction of workers, etc.) and technical measures (explosion protection measures).

Standards

European Standards EN 50014 - EN 50020 on electrical equipment were issued in 1978 and replaced the national standards for this equipment valid up until then Europe-wide. In addition to the standards for electrical equipment published by the CENELEC, corresponding standards for non-electrical explosion-protected equipment have since been developed by the CEN.

According to an agreement between the European Committee for Electrotechnical Standardization CENELEC and the International Electrotechnical Commission IEC, the European standards for electrical equipment have been adopted unchanged by the IEC for several years. The European standard series EN 50014, which defines the requirements on equipment to be used in explosive gas atmospheres, will be gradually replaced by the European standards series EN 60079. These standards have been issued as VDE 0170 in Germany.

The requirements on types of protection for areas where combustible dust may occur are specified in standard series IEC 61241. In Europe, these standards replace the old series EN 50281 as EN 61241. Since many requirements are identical to the standards for explosive gas atmospheres, both standard series will be summarized in series IEC or EN 60079.

Electrical apparatus for explosive gas atmospheres:

EN (old) EN (new) IEC
General requirements EN 50 014 EN 60079-0 IEC 60079-0
Flameproof enclosures "d" EN 50 018 EN 60079-1 IEC 60079-1
Pressurized enclosures "p" EN 50 016 EN 60079-2 IEC 60079-2
Powder filling "q" EN 50 017 EN 60079-5 IEC 60079-5
Oil immersion "o" EN 50 015 EN 60079-6 IEC 60079-6
Increased safety "e" EN 50 019 EN 60079-7 IEC 60079-7
Intrinsic safety "i" EN 50 020 EN 60079-11 IEC 60079-11
Protection type "n" EN 50 021 EN 60079-15 IEC 60079-15
Encapsulation "m" EN 50 028 EN 60079-18 IEC 60079-18
Intrinsically safe systems EN 60079-25 IEC 60079-25
Electrical equipment for zone 0 EN 50 284 EN 60079-26 IEC 60079-26
Intrinsically safe fieldbus systems EN 60079-27 IEC 60079-27
Optical radiation "op" EN 60079-28 IEC 60079-28

Electrical apparatus for use in the presence of combustible dust:

EN (old) EN (new) IEC (new) IEC (old)
General requirements EN 61241-0 IEC 61241-0 IEC 61241-1-1
Protected by enclosures "tD" EN 50281-1-1 EN 61241-1 IEC 61241-1 IEC 61241-1-1
Pressurized enclosures "pD" EN 61241-2 EN 61241-2 EN 61241-4
Intrinsic safety "iD" EN 61241-11 IEC 61241-11 EN 61241-5
Encapsulation "mD" EN 61241-18 IEC 61241-18