Explosion-proof knowledge technology

First, explosion-proof electrical equipment explosion-proof type

Explosive mixture explosion conditions

Explosion refers to the light and heat or mechanical work that a substance undergoes from a state that has undergone physical or chemical changes, suddenly becomes another state, and emits enormous energy. Only the explosion of explosive mixtures is mentioned here, ie the explosion of all combustible gases, vapours and explosive mixtures of dust and air. Such explosions require three conditions at the same time to occur: first, there must be explosive or flammable substances; second, there must be flammable substances, mainly oxygen in the air; and third, there must be ignition Sources (such as sparks, arcs, and dangerous temperatures, etc.) that provide the necessary energy to ignite the mixture. Only if these three conditions exist at the same time will there be the possibility of an explosion. If any of these conditions is not met, there will be no burning or explosion. Therefore, taking appropriate measures so that the three conditions are not met at the same time can achieve the purpose of preventing explosions. Because explosive mixtures are commonly found in places such as coal, petroleum, chemicals, textiles, food processing and other industries where they are produced, processed, stored and transported, explosions are extremely harmful. As a result, people adopted a variety of explosion-proof technology methods to prevent the formation of explosive dangerous environments and their explosions.

2. Basic explosion-proof type

(1) Flameproof type "d"

Explosion-proof type explosion-proof type is to completely enclose the parts of the equipment that can ignite the explosive gas mixture in a shell whose outer shell can withstand any joint or structural gap through the shell, and the flammable mixture that penetrates inside the shell is exploded inside without damage. It does not cause ignition of externally explosive atmospheres formed by one or more gases or vapours (see GB 3836 2).

Place parts that may generate sparks, arcs, and dangerous temperatures into a flameproof enclosure that isolates the interior of the equipment from the surrounding environment. There is a gap in the flameproof enclosure. Due to the respiration of the electrical equipment and the gas permeation, an explosive gas mixture may exist inside. When the explosion occurs, the enclosure can withstand the explosion pressure generated without damage, and at the same time, the gap of the shell structure can cool the flame and lower the flame. The speed of flame propagation or the acceleration of the chain is such that flame or dangerous flame products cannot ignite the external explosive atmosphere through the flameproof gap, thereby achieving the purpose of flameproof.

The explosion-proof type “d” is classified into Type I and Type IIA, Type IIB, and Type IIC according to the types of explosive gas atmospheres it is allowed to use.

This type of explosion-proof equipment is suitable for use in places 1 and 2.

(2) Increased Safety "e"

Increased safety type is a kind of extra protection for electric equipment that will not generate electric arc and spark under normal operating conditions to increase its safety and prevent the possibility of dangerous temperatures, arcs and sparks in its internal and external parts. The explosion-proof version. It does not include equipment that generates sparks or arcs under normal operating conditions (see GB 38363 standard).

In the normal operation of the electrical equipment structure that will not produce sparks, arcs and dangerous temperatures, by taking measures to reduce or control the operating temperature, ensure the reliability of the electrical connection, increase the insulation effect and improve the degree of protection of the enclosure to reduce pollution due to dirt The possibility of entering and the introduction of moisture, etc., to reduce the possibility of causing ignition failure, and improve the safety and reliability of the equipment in the normal operation and the provisions of the fault (for example, the rotor locked rotor). 〖JP〗

This type of equipment is mainly used in hazardous areas in Zone 2 and some types can be used in Zone 1, such as increased safety low voltage asynchronous motors with suitable protection devices, junction boxes, etc.

(3) Intrinsically safe "i"

The intrinsically safe explosion-protected version is that all circuits inside the equipment are intrinsically safe from the prescribed explosive gas atmospheres that cannot be ignited by any spark or any thermal effect that occurs under standard conditions (including normal operation and specified fault conditions). Circuit. 〖HTH〗 "i" grade electrical equipment 〖HT〗 is an intrinsically safe electrical equipment that cannot cause ignition under normal operating conditions and with both a fault and an arbitrary combination of two fault conditions; 〖HTH〗 class ib electrical equipment HT is an intrinsically safe electrical device that does not cause ignition under normal operating conditions and by applying a fault condition (see GB 38 364 standard).

The intrinsically safe type starts from limiting the energy in the circuit. The potential spark energy is reduced to the ignitable prescribed gas mixture energy by reliable control circuit parameters, and the surface heating temperature of the wire and component is limited to the ignition temperature of the specified gas mixture. under.

This explosion-proof type can only be applied to weak electrical equipment. This type of equipment is suitable for Zones 0, 1, 2 (Ex i) or Zone 1 (E x ib).

(4) Positive pressure type "p"

An explosion-proof version of electrical equipment. It is an electrical device that achieves safety by keeping the pressure of the protective gas inside the device enclosure higher than that of the surrounding explosive atmosphere (see GB 38365).

Positive pressure equipment protection can use different methods. One approach is to protect the static positive pressure inside the system, and the other is to maintain a constant flow of air or inert gas to limit the entry of the flammable mixture into the interior of the enclosure. Both methods require flushing of the enclosure with protective gas prior to start-up of the device to remove flammable gases in the enclosure when the device is in a non-positive pressure state to prevent the formation of a flammable mixture within the enclosure. The main point of these methods is to monitor the system and conduct regular ventilation to ensure the reliability of the system.

Such equipment can be used in hazardous areas in Zone 1 or Zone 2 according to the protection method.

(5) Oil-immersed type "o"

Oil-immersed explosion-proof type is to immerse the whole equipment or parts of the equipment in the oil (protection fluid) so that it cannot ignite the explosive gas atmosphere above the oil surface or outside the housing (see GB 38366 standard).

This is an old explosion-proof technology method that is mainly used for switchgear. The arc and sparks formed are immersed in oil.

This type of equipment is suitable for hazardous areas in Zone 1 or Zone 2.

(6) Sand-filled "q"

The sand-filled explosion-proof type is a type of electrical equipment in which the outer shell is filled with sand or other specified powder material so that the arc or high temperature generated in the shell cannot ignite the surrounding explosive gas atmosphere under the specified conditions of use (see GB 38367 standard).

This explosion-proof version fixes and completely buries the conductive parts of the explosive gas atmosphere and completely embeds them in the sand-filled material, thereby preventing the propagation of sparks, arcs and dangerous temperatures, making it impossible to ignite the external explosive atmosphere. It is typically used for components and heavy-duty traction battery packs in Ex "e" or Ex "n" devices.

This type of equipment is suitable for hazardous areas in Zone 1 or Zone 2.

(7) "n" type explosion-proof electrical equipment

This type of electrical equipment can not ignite the surrounding explosive gas environment during normal operation, nor is it likely to cause ignition failure (see GB 38368 standard).

When the "n" type electrical equipment is in normal operation, it means that the equipment is electrically and mechanically conforming to design specifications and used within the range specified by the manufacturer, and it is impossible to generate sparks, arcs, and dangerous temperatures.

Explosion-proof explosion-proof box physical map

Increase safety type explosion-proof box physical map

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