Explosion protection

"Explosion protection" covers a range of measures and methods aimed at preventing explosions in environments where flammable gases, vapors, dust or fibers may be present, and at mitigating the consequences in the event of an explosion. This term does not necessarily mean that the equipment can withstand an external explosion, but rather that it can contain any internal explosion and prevent it from spreading to the surrounding explosive atmosphere. The main objective of explosion protection is to prevent explosions and minimize their consequences for people, property and the environment. It is important to note that while international explosion protection standards and best practices are globally relevant, specific local regulations may also apply depending on the industry and context.

Explosion protection includes the following main aspects:

1. Prevention of the formation of an explosive environment (primary explosion protection):

Elimination or replacement of flammable substances with non-flammable or less flammable ones.

Reduction of the content of flammable substances in the atmosphere of safe results (e.g. by means of ventilation).

Prevention of release of flammable substances into the environment (e.g. by means of sealed equipment).

Inertness of the environment by means of addition of hazardous gases (e.g. nitrogen, carbon dioxide).

2. Prevention of ignition of explosive atmospheres (secondary explosion protection):

Use of explosion-proof equipment, the design of which eliminates the possibility of sparks, arcs or unacceptably high temperatures, increased light, optical, radiation and radio emissions.

Also eliminating ignition sources such as:

open flames and hot surfaces,

mechanical sparks (e.g. from impact or friction),

static electricity,

adiabatic compression,

chemical reactions.

Basic principles of explosion-proof design:

Containment: The equipment body is strong enough to contain the internal explosion without collapsing or allowing the explosion to escape.

Separation/Exception: Prevention of contact of a combustible substance with a potential source of ignition. This can be achieved through sealed enclosures, encapsulation, or immersion in a protective liquid.

Energy limitation (intrinsically safe): limiting the electrical energy inside the equipment to a level that is too low to cause ignition, even under fault conditions.

Avoidance: Designing equipment that, during normal operation, does not create potential ignition sources such as sparks or excessive heat.

Cooling: Ensuring that the surface temperature of the equipment remains below the ignition temperature of the surrounding flammable materials.

3. Localization and limitation of explosion consequences (tertiary explosion protection):

Explosion-resistant structures that can withstand the pressure of an explosion.

Explosion pressure relief devices (e.g., pressure relief valves, diaphragms) that direct the energy of an explosion to a safe location.

Explosion suppression systems that rapidly inject inhibitors to prevent the spread of flame.

Fire suppression systems to extinguish fires that occur after an explosion.

Planning and zoning of hazardous areas to minimize the impact of an explosion on surrounding facilities and personnel.

Standards and regulations

There are various international and national standards in the field of explosion protection, such as IECEx (international system), ISO (international standards), ATEX (European Union), UL and CSA standards (North America) and others. These standards set requirements for the design, testing and marking of explosion-proof equipment.

Some key regulatory frameworks include:

• IECEx (International): an international certification system for equipment intended for use in explosive atmospheres.

• ATEX (Europe): A set of directives covering equipment and protective systems intended for use in potentially explosive environments.

• NEC (North America): The National Electrical Code of the USA contains recommendations for electrical installations in hazardous areas.

• CSA (North America): standards of the Canadian Association of Standards for Electrical Safety in Hazardous Areas.

These standards classify hazardous areas into zones or divisions based on the likelihood and duration of the presence of explosive atmospheres, which then dictates the type of explosion protection required for equipment used in those areas. Equipment is also often marked with special codes indicating the type of protection, equipment group and temperature class to ensure its suitability for the intended hazardous environment.

Compliance with explosion protection requirements is critical to ensuring safety in enterprises where there is a risk of explosive atmospheres. Compliance with international and national standards is critical to ensuring the safety of explosion-proof equipment and installations.