Presenting conditions for forming NHCN environment in equipment using or related to combustible dust

Presenting conditions for forming NHCN environment in equipment using or related to combustible dust

• Explosion-hazardous environment is an environment in which there is a mixture of combustibles and oxidants whose concentration value is within its flammable concentration range. Hazardous environment of fire and explosion can form inside equipment containing flammable substances under normal operating conditions:
• In sealed equipment containing flammable liquids
• In equipment containing combustible gases
• In equipment that uses or involves combustible dust
• During the period of stopping or starting the equipment to put into operation

*The fire hazard of dust:

Dust has small size, ability to absorb heat and catch fire quickly. When a fire occurs, it spreads quickly. Dust is capable of hovering, clinging to the surface of equipment, construction components, even going deep. into complicated places and so it's very difficult to fight a fire when fighting. Dust has the ability to combine with air to form explosive mixtures.

*Conditions to form a dangerous and explosive environment

• In the production conditions of crushed solid combustibles, it can be the final product such as wood pulp, rice flour, wheat flour, etc. The particle size is very diverse, depending on the particle size and the transfer speed. air movement in which dust is suspended or deposited on production surfaces. The deposited dust is capable of smoldering and igniting. Suspended dust combines with oxygen to form a flammable and explosive mixture.
• To assess the fire and explosion hazard of suspended dust, it is based on the quantity of low flammability limit of dust because the limit of high flammability concentration of dust is very large and in practice is rarely reached. Therefore, the conditions for existence of explosive and explosive concentrations of dust will be:
• Ctt Cth

Ctt : Actual concentration of dust

Cth : Limit of low flammability of dust

Conditions for fire and explosion safety when operating dust-containing equipment:

                Cth

Clvat

                Kat

Kat : factor of safety Kat ≥2

(The above material is updated from the University of Fire Protection)