Dalan Motor explained the key knowledge of explosion-proof motors. If you don't collect it, you will lose money!
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After the explosion accident, it is often more serious. The collapse of the building and the destruction of the equipment have caused a large loss of state property and inadvertently caused injuries. The following is the importance and necessity of the explosion prevention work. .
First, the reasons for the explosion-proof considerations
Explosive substances: Some flammable substances are produced in many production sites. About two-thirds of the mines in the coal mine have explosive substances. In the chemical industry, about 80% of the production workshops have explosive substances.
Oxygen: Oxygen in the air is ubiquitous.
Ignition source: The use of electrical instruments in the production process, a variety of friction sparks, mechanical wear sparks, static sparks, high temperatures, etc. are inevitable, especially when the instrument and electrical failure. Objectively, many industrial sites meet the explosion conditions. When the mixed concentration of explosive substances and oxygen is within the explosion limit, if there is a source of explosion, an explosion will occur. Therefore, it is necessary to take explosion protection.
Second, the basic concept of explosion-proof motor
An electric motor that does not ignite in an explosive surrounding environment under specified conditions.
Category of electrical equipment for explosive atmospheres: categories classified according to the explosive environment in which electrical equipment is used:
Class I: used in coal mine gas environment;
Class II: Other explosive atmospheres other than coal mine gas;
Class III: Explosive dust environment other than coal mines.
Class II: Marked as ExdIIAT4, ExdIIBT4, ExdIICT4; in Class II products, IIB motors can replace IIA motors, and IIC motors can replace IIB and IIA motors.
Maximum surface temperature: The maximum temperature reached by any component or any surface of an electrical device when operating under the most adverse operating conditions (but within the specified tolerances).
Note: For electrical equipment used in explosive atmospheres, this temperature may appear on the internal components of the equipment or on the surface of the enclosure, depending on the type of explosion protection.
Temperature group: A group of electrical equipment in an explosive environment divided by its maximum surface temperature.
Explosive environment: Under atmospheric conditions, a mixture of flammable substances in the form of gases, vapors, dust, fibers or fly ash is ignited to maintain a self-propagating environment.
Explosive atmosphere: Under atmospheric conditions, a mixture of flammable substances in the form of gases or vapors with air can be ignited to maintain a self-propagating environment.
Zone 0 in the division of hazardous areas: areas where explosive or explosive atmospheres occur continuously or in the long term. The location belonging to Zone 0 is very small in engineering, for example, the space between the top of the tank with the exhaust port and the oil surface belongs to Zone 0.
Zone 1 in the hazardous area division: An area where an explosive atmosphere may occur during normal operation. For example, a sampling valve for a flammable gas or liquid on a process unit in a production plant belongs to Zone 1. According to the relevant information, the probability of occurrence of explosive gas environment in Zone 1 is about 10-1~10-3, that is, about 1 hour per shift, and about 10~1000 hours per year.
Zone 2 in the hazardous area division: An area where an explosive atmosphere is unlikely to occur during normal operation, and if it does, it exists for a short period of time. For the frequency and duration of occurrence of the flammable gas environment in Zone 2, the probability of introduction is about 10-4, that is, about 1 hour per year.
Third, other knowledge
For Class I electrical equipment, the maximum surface temperature shall not exceed 150 °C when coal dust may accumulate on the surface of electrical equipment; when the surface of electrical equipment does not accumulate or measures are taken to prevent accumulation of coal dust, the maximum surface temperature shall not exceed 450 °C. .
For Class II electrical equipment, the temperature is divided into T1 ~ T6 group, the highest temperature is 450 ° C, 300 ° C, 200 ° C, 135 ° C, 100 ° C, 85 ° C.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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