Non-electrical explosion protection

An analysis for manufacturers and users

Author: Herbst, S.; Gerlach, J.; Engelmann, F.: Ernst-Abbe-Hochschule, Jena

Non-electrical explosion protection includes designing non-electrical devices, components and systems, such as stirring devices, screw conveyors or pneumatically operated filling systems, so that they are explosion-protected. Alongside electrical explosion protection, this sector is a significant consideration for manufacturers of explosion-protected products and operators of systems at risk from explosions. In many projects within product development and systems planning, this area of explosion protection leads to high levels of additional work and expenditure, which are not taken into account at the start of the project. For instance, an ignition hazard assessment must be performed, operating instructions must be made more comprehensive, and additional training for enhancing and updating knowledge are required. For these reasons, manufacturers and users must acquire knowledge on the subject of non-electrical explosion protection, in order to assess the application, expenditure and responsibility objectively and realistically.

Explosion protection in Europe is primarily governed by the ATEX directive. Compliance with these explosion protection specifications in accordance with this directive is clearly defined. The ATEX directive applies to (ATEX Directive 2014/34/EU, Art. 1, para. 1):

"Equipment and protective systems intended for use in potentially explosive atmospheres;
safety devices, controlling devices and regulating devices intended for use outside potentially explosive atmospheres but required for or contributing to the safe functioning of equipment and protective systems with respect to the risks of explosion;
components intended to be incorporated into equipment and protective systems referred to in point (a)."

In this case, the "equipment" product class encompasses a comprehensive, diverse range, as it includes "machines, apparatus, fixed or mobile devices, control components and instrumentation thereof and detection or prevention systems" (ATEX Directive 2014/34/EU, Art. 2, para. 1). One of the most important prerequisites of the application of the ATEX Directive, however, is the presence of an intrinsic potential source of ignition on the device. This condition means that the ATEX Directive applies to both electrical and non-electrical explosion protection. However, it must be checked whether its application is mandatory. When it comes to pneumatics, for instance, non-certified hoses or screw connections can be used in certain hazardous areas because they have no intrinsic potential source of ignition and are therefore products that are not subject to approval. However, it must be noted here that the interfaces between the component and the environment must be assessed within the context of an ignition hazard assessment of the entire device for explosion protection purposes. In this specific example, contaminated compressed air flowing through pneumatic hoses could, in a worst case scenario, generate an electrostatic charge.
One of the most significant hazards in non-electrical explosion protection is the risk of a potential source of ignition becoming an effective source of ignition.
As a result, in the case of non-electrical devices, the ignition hazard assessment is used to assess and analyse all potential sources of ignition on a device, which are then eliminated or minimised to a harmless level by implementing measures. The ignition hazard assessment is the key methodology involved in non-electrical explosion protection. It comprises five basic steps and requires comprehensive knowledge and experience. This method cannot be applied universally; instead, it must be specifically performed and formally documented during the development phase for every individual product and variant thereof. This requirement is stipulated in the ISO 80079-36 standard, which is harmonised with the ATEX directive.
The standard ISO 80079-36 "Non-electrical equipment for explosive atmospheres – Basic method and requirements" has formed the normative basis for non-electrical explosion protection internationally since December 2016. However, the standard IEC 60079-0 also applies, as the basic explosion protection standard. Firstly, the requirements of the types of protection for non-electrical explosion protection are set out in ISO 80079-37 for the constructional safety, control of ignition sources and liquid immersion types of protection. Secondly, electrical explosion protection standards apply to the pressurized enclosure (IEC 60079-2), protection by enclosure (IEC 60079-31) and flameproof enclosure (IEC 60079-1) types of protection, since these types of protection can be used in both electrical and non-electrical explosion protection. This structure originated in the new ISO 80079 international standards series. Before this, the EN 13463 standards series applied in Europe, individual parts of which governed the specific requirements and types of protection for non-electrical explosion protection.

There are also significant differences between electrical and non-electrical explosion protection with respect to the conformity assessment and certification process. According to the requirements of the ATEX directive (Section 3), the conformity of non-electrical devices in device category 3 can be established while taking into consideration additional conditions imposed by the manufacturer's own assessment. Electrical explosion-protected devices in device category 2 must pass an EU type examination performed by a notified body. The assessment of non-electrical explosion-protected devices in device category 2 can be performed while considering additional conditions imposed by the manufacturer. Only the technical documentation must be stored with a notified body. An EU type examination must only be performed by a notified body for non-electrical explosion-protected devices in device category 1. Alternatively, however, an individual examination can always be performed by a notified body, regardless of the device category.
The product can be sold on the European market once it has successfully passed a conformity assessment in accordance with the ATEX directive. For international sales, the requirements set out in the individual national regulations must be observed. This may mean that conformity tests are required in the individual distribution countries. The use of the IECEx system is intended to minimise this additional work. The IECEx system is a sub-organisation within the International Electrical Commission (IEC) and is based on the IEC's standards and norms. The required inspections are performed in a recognised laboratory and certification is performed by a recognised inspection authority. The certificate produced and the corresponding test reports can be used as the basis for national certification, which enables the expenditure and work required for inspection to be minimised. The publication of the international standards ISO 80079-36 and -37 established a basis for certification for non-electrical explosion-protection devices within the IECEx system, since these standards are also recognised by the IECEx system. The standards are developed by representatives of the IEC, among other contributors. Accordingly, non-electrical devices can now obtain conformity in accordance with ATEX directives and certification according to IECEx. However, there is one more detail that must be taken into consideration when meeting these requirements. Within the framework of the ATEX directive, the application of the standards is not mandatory. Other technical solutions that meet the requirements of the ATEX directive are also possible; however, there is no presumption of conformity in this case. The standards must be applied within the framework of the IECEx system.

Illustration: Marking of non-electrical equipment

The specified aspects of the ignition hazard assessment, types of protection and declaration of conformity must be taken into account by the manufacturer. If explosion-protected devices are developed and manufactured by users for their own use, these aspects and, since ATEX 2014/34/EU came into force, their requirements must be fully met. The user becomes a manufacturer. On the other hand, if users combine products that have already obtained conformity assessment in accordance with manufacturer's instructions, user directive 1999/92/EC, the German Ordinance on Industrial Safety and Health and the German Ordinance on Hazardous Substances must be taken into account. In this case, the fundamental safety requirements in the generally applicable guidelines must be fulfilled, as per the German Ordinance on Industrial Safety and Health (Section 5, paragraph 3). This is verified by the manufacturer's conformity assessment. As a result, the independent conformity assessment is not applicable. However, an inspection of the interfaces is always recommended. A conformity assessment procedure in accordance with the Machinery Directive, taking explosion protection into account, is mandatory.
Within the scope of non-electrical explosion protection, users must always observe all technical documentation and operating instructions for the devices. Non-electrical explosion protection solutions are, on account of their wide range of applications and variants, unique and variable. Safe operation of a non-electrical device can be ensured through the implementation of constructive measures. In some cases, this can result in solutions that are too large or not cost-effective, or even technically infeasible. Explosion-protected operation is then guaranteed through the use of organisational measures. For instance, maintenance intervals are shortened in order to detect hazardous wear and tear in good time, thereby preventing a potential source of ignition from becoming an effective source of ignition. As well as the explosion protection documentation and inspections according to the German Ordinance on Industrial Safety and Health, the user must take into account these essential instructions regarding the safe use of non-electrical devices.

In summary, manufacturers and users of non-electrical explosion protection products must have comprehensive knowledge of this branch of explosion protection, in order to implement all requirements and methods in a responsible manner. The extensive scope of non-electrical explosion protection means that this sector is continuously evolving. As a result, all persons involved must regularly learn and update their knowledge by attending training sessions and conferences.

References

EUROPEAN PARLIAMENT AND COUNCIL (29.03.2014): DIRECTIVE 2014/34/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 26 February 2014 on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast). ATEX 2014/34/EU.

Standard DIN EN ISO 80079-36, 2016: Explosive atmospheres – Part 36: Non-electrical equipment for explosive atmospheres – Basic method and requirements (ISO 80079-36:2016); German version EN ISO 80079-36:2016

Standard DIN EN ISO 80079-37, 2016: Explosive atmospheres – Part 37: Non-electrical equipment for explosive atmospheres – Non-electrical type of protection constructional safety ''c'', control of ignition sources ''b'', liquid immersion ''k'' (ISO 80079-37:2016); German version EN ISO 80079-37:2016

DIRECTIVE 1999/92/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 December 1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC)

Regulation on safety and health protection when using work equipment (German Ordinance on Industrial Safety and Health – BetrSichV); German Ordinance on Industrial Safety and Health of 3 February 2015 (BGBl. [Federal law Gazette] I, p. 49), which has most recently been amended by Article 1 of the regulation of 30 April 2019 (BGBl. I, p 554)

Regulation on protection from hazardous substances (German Ordinance on Hazardous Substances – GefStoffV); German Ordinance on Hazardous Substances of 26 November 2010 (BGBl. I, p. 1643, 1644), which has most recently been amended by Article 148 of the Act of 29 March 2017 (BGBl. I, p. 626)

Essential Explosion Protection, Publication of R. STAHL Schaltgeräte GmbH: Marking of non-electrical equipment, page 53