The Ignition Hazard Assessment report and Dust Explosion Analysis

When talking about explosive atmospheres, the distinction between potential and effective ignition source is very important. A potential ignition source is a source in the equipment that has the ability to ignite an explosive atmosphere. An effective ignition source, on the other hand, is an ignition source that is actually capable of igniting an explosive atmosphere. Therefore, when assessing ignition hazards, it should be considered that the sources listed below can be both potential and effective sources of ignition:

• Warm surfaces,
• Flames and hot gases,
• Mechanically generated sparks,
• Electrical sources,
• Leakage currents,
• Static electricity,
• Lightning,
• Electromagnetic waves from 104 Hz to 3 x 10 12 Hz from radio frequency radiation,
• Electromagnetic waves including optical radiation from 3 x 1011 Hz to 3 x 1015 Hz,
• Ionising radiation,
• Ultrasound,
• Adiabatic compression and shock waves,
• Exothermic reactions, including spontaneous combustion of shock waves.

Dinnissen analyzes and tests all these components in a so-called Dust Explosion Analysis (DEA). In general terms, such an ignition hazard study and assessment is often referred to as the Ignition Hazard Assessment. It identifies all potential ignition sources that could occur during normal use, an expected failure and a rare failure. A rare fault is understood to mean a fault between two independent expected faults that only cause an ignition source in combination, not separately from each other. Depending on the outcome of the DEA, the equipment is classified under one of the following Equipment Protection Level (EPL):

Group I: Equipment for mines susceptible to mine gas contains 2 EPLs: Ma and Mb.

Group II: Equipment for locations with an explosive atmosphere caused by mixtures of air with gas, vapors or mist. This group contains 3 EPLs: Ga, Gb, Gc. In addition, this group is further subdivided based on the nature of the explosive gas atmosphere into: IIA (propane), IIB (ethylene), IIC (hydrogen).

Group III: Equipment for locations with an explosive atmosphere caused by mixtures of air with another combustible substance. This includes 3 EPLs: Da, Db and Dc. This group is also subdivided based on the nature of the explosive dust atmosphere into: IIIA (suitable for flammable dust particles), IIIB (suitable for flammable dust particles and a non-conductive dust), IIIC (suitable for flammable dust particles, a non-conductive dust conductive and conductive fabric).

Equipment that passes the Ignition Hazard Assessment and which has been confirmed to not generate effective ignition sources under normal use may be classified as EPL Gc or Dc. If the investigation shows that the equipment does not contain effective ignition sources under normal use and even under anticipated failures, then it falls under the EPL Mb, Gb or Db category. If it appears that in addition to normal operation and expected failures, there is also no potential for effective ignition sources during rare failures, then the equipment falls under EPL Ga or Da. Depending on the equipment's EPL, mitigation can be applied to any of the potential ignition sources to further reduce the likelihood of them becoming effective ignition sources.

The Ignition Hazard Assessment report or DEA contains at least the following points:

• Basic information such as a description of the equipment and materials,
• Identified hazards and their causes,
• Investigation of the ignition hazard,
• Means for removing or minimizing ignition hazards,
• Result of the definitive ignition hazard assessment and any reasons for this,
• Other hazards requiring action,
• the EPL as a result and the necessary restrictions when it comes to safety.

The installations and machines that Dinnissen produces are mainly located in groups II and III. 90% of the products that are processed in Dinnissen's machines fall under category IIIB. From now on, therefore, only the conditions of groups II and III will be discussed.