The specific meaning of explosion-proof signs used in flammable and explosive dust environment
Explosion-proof mark refers to the mark used to describe the explosion-proof grade, temperature group, explosion-proof type and applicable area of u200bu200bexplosion-proof electrical equipment. Let's analyze the specific meaning of the letters in the explosion-proof signs in the dust environment.
1. Explosion-proof type classification of electrical equipment for explosive dust environment
In explosive dust environment, the explosion-proof type in the explosion-proof mark is divided into intrinsic safety type 'iD
Shell protection type 'tD'
The explosion-proof safety performance of enclosure-protected electrical equipment mainly depends on the enclosure of the equipment to ensure that the explosive dust layer or dust cloud enters the inside of the equipment, thereby preventing the dust layer or dust cloud from being ignited.
Intrinsically safe 'iD'
The explosion-proof safety performance of intrinsically safe electrical equipment is mainly realized by limiting the energy of the circuit to achieve explosion-proof. In this kind of electrical equipment, even if the circuit is short-circuited, open-circuited, insulation breakdown and other faults caused by electrical discharge and thermal effects, etc., can not cause the explosive dust mixture to ignite.
Positive pressure protection type 'pD'
The anti-explosion safety performance of positive pressure protection electrical equipment depends on filling the electrical equipment with a protective gas with a certain pressure, so that the electrical components that may generate sparks, arcs, and dangerous temperatures are in the protective gas Among them, in this way, the combustible dust cloud cannot enter the inside of the equipment, and these components will not have the risk of igniting the explosive dust mixture.
Pouring protection type 'mD'
The explosion-proof safety performance of encapsulated electrical equipment is to use encapsulating compound to encapsulate the protected electrical components to prevent these components from contacting the surrounding combustible dust, so as to prevent it from igniting the surrounding explosive dust environment .
2. Classification of the use environment of electrical equipment for explosive dust environment
Class III electrical equipment is used in explosive dust environments except coal mines
Class III electrical equipment reclassification:
ⅢA category: flammable fly flies.
ⅢB category: non-conductive dust.
ⅢC category: conductive dust.
According to the frequency and duration of the explosive dust/air environment, the explosive dust environment is divided into 20, 21, and 22 zones.
Zone 20: A place where an explosive environment in the air continuously appears in the form of a flammable dust cloud, exists for a long time or appears frequently.
21 Zone: During normal operation, an explosive environment in the air may appear or occasionally appear in the form of a flammable dust cloud.
22: In the normal operation process, an explosive environment in the air is unlikely to appear in the form of a flammable dust cloud. If it occurs, it will only exist for a short time.
3. Maximum surface temperature of electrical equipment used in explosive dust environment
The maximum surface temperature specified by should be higher than the measured maximum surface temperature and lower than the ignition temperature of the specific combustible dust layer or dust cloud to be used.
Fourth, the classification of the protection level of electrical equipment used in explosive dust environments
Da—With a 'high' protection level, the equipment is not a source of ignition during normal operation, expected failures or rare failures.
Db—With a 'high' protection level, the equipment is not a source of ignition during normal operation or an expected failure.
Dc—has a 'general' protection level. The equipment is not an ignition source during normal operation. Some additional protective measures can also be taken to ensure that effective ignition will not occur when the ignition source is expected to occur frequently.
From the above description, it can be seen that the dust explosion-proof mark and the gas explosion-proof mark have many common points, and many of the explosion-proof test items are also figured out, so I won't repeat them here.
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