Is Class 1 Division 1 Explosion Proof?
“Hazardous locations” encompass areas where ignitable concentrations of flammable gas, whether in vapor or liquid form, may be present, posing a risk of explosion when exposed to a sufficient source of spark or thermal energy. These locations are classified based not only on the types of volatile substances present but also on the likelihood of their presence at any given time.
Electrical equipment remains necessary in hazardous locations despite the associated risks. Hot surfaces and electrical or mechanical sparks are two features of electrical equipment that could potentially ignite flammable or combustible gases in such environments. Designing electrical equipment for hazardous locations involves considering the risks of explosion as well as general safety requirements like electrical shock, fire hazards, and injuries.
In North America, the Class/Division system categorizes the nature of hazardous locations and the degree of risk involved. “Class I” denotes the presence or possibility of hazardous substances such as flammable and/or combustible liquids, gases, or vapors, indicating a danger of explosion due to the presence of flammable gas or vapor. “Division 1” signifies a location where an explosive atmosphere exists continuously, for extended periods, or frequently.
Electrical devices intended for installation in Class I Division 1 hazardous locations must be protected against the risk of explosion. Protection techniques typically involve containment, energy limitation, and isolation of the ignition source from the explosive atmosphere. These methods aim to contain an internal explosion or eliminate one or more components necessary for an explosion to occur.
- Explosion Proof Equipment: This method employs containment by utilizing explosion-proof or ignition-proof enclosures along with proper seals for cables and conduits to enclose any parts capable of igniting an explosive gas. The enclosure can withstand the pressure resulting from an explosion, preventing its spread to the surrounding atmosphere.
- Intrinsically Safe: This technique ensures that insufficient electrical or thermal energy is released to cause ignition, rendering circuits and interconnecting wiring incapable of causing an explosion. It serves as an energy limitation strategy.
- Purging and Pressurization: This approach isolates potential ignition sources from the explosive atmosphere by pressurizing electrical equipment. Flammable gases are prevented from entering enclosures containing electrical devices. Purged and pressurized enclosures operate by removing residual gas or vapor before powering on (purge cycle) and maintaining positive pressure inside the enclosure during operation (pressurizing cycle), ensuring that the protective gas pressure exceeds that of the surrounding atmosphere.
What is explosion proof equipment. Examples of Class I Division 1 products and commonly used
protection methods include explosion-proof enclosures, intrinsically safe
circuits, and purged and pressurized electrical equipment. Relevant North
American standards apply to these types of electrical equipment.
