Explosion-proof electrical types are divided into two types according to the different use environment: one is electrical equipment used in underground coal mine; The second category is electrical equipment used in factories. Depending on the characteristics of electrical equipment that produce sparks, arcs and hazardous temperatures, and the measures taken to prevent them from igniting explosive mixtures,
Divided into the following eight forms:
(1) Flameproof type (mark D) : it is a kind of electrical equipment with flameproof shell, whose shell can withstand the explosive pressure of the internal explosive gas mixture to prevent the internal explosion to the explosive mixture around the shell. It can be used in any explosive hazard site.
(2) Increased safety type (mark E) : under normal operating conditions, there will be no arc, spark, nor high temperature enough to ignite explosive mixtures. Structural measures to improve safety to avoid arcs, sparks and high temperatures under normal and accepted overload conditions.
(3) Intrinsically safe type (mark IA, IB) : using IEC76-3 spark test device. The specified explosive mixture shall not be ignited by sparks or thermal effects generated during normal operation or specified failure conditions. The electrical equipment is classified into TWO grades, IA and IB, according to the place of use and the degree of safety. Class IA equipment cannot ignite explosive gas mixtures during normal operation, one failure and two failures. Class IB equipment cannot ignite explosive gas mixtures during normal operation and a failure.
(4) Positive pressure type (mark P) : it has a positive pressure shell, can keep the internal protective gas, namely fresh air or inert gas pressure is higher than the surrounding explosive environment pressure, prevent the external mixture into the shell.
(5) Oil-filled type (mark U) : It is to soak all or part of the electrical equipment in oil, so that the equipment can not point above the fuel surface or outside the shell of the explosive mixture. Such as high pressure oil switch is such.
(6) Sand filling type (mark Q) : the shell is filled with sand material, so that under certain conditions of use, the arc generated in the shell, the flame spread, the shell wall or sand material surface and the overheating can not ignite the surrounding explosive mixture.
(7) Non-spark type (symbol N) : under normal operating conditions, it will not ignite the surrounding explosive mixture, and generally will not occur with ignition failure.
(8) Special type (mark S) : refers to the explosion-proof electrical equipment which does not belong to any of the above categories in structure and adopts other special explosion-proof measures. Such as filling stone sand type of equipment is such.
