Motor explosion-proof grade
Explosion-proof motors are mainly used in coal, oil and gas, petrochemical and chemical industries. In addition, it is also widely used in textile, metallurgy, city gas, transportation, grain and oil processing, papermaking, medicine and other sectors. As the main power equipment, explosion-proof motors are usually used to drive pumps, fans, compressors and other transmission machinery.
Motors can be divided into flameproof motors, increased safety motors, positive pressure motors, non-sparking motors and dust explosion-proof motors according to the principle of explosion protection.
Explosion concept
In a very short time, a large amount of energy is released, high temperature is generated, and a large amount of gas is released, causing a high-pressure chemical reaction or state change in the surrounding medium. The rapid release of energy will subject surrounding objects to violent impact and destruction.
Three conditions must be met for an explosion: 1) Explosive substances: substances that can react with oxygen (air), including gases, liquids and solids. (Gas: hydrogen, acetylene, methane, etc.; liquid: alcohol, gasoline; solid: dust, fiber dust, etc.) 2) Oxygen: air. 3) Ignition source: including open flame, electrical spark, mechanical spark, static spark, high temperature, chemical reaction, light energy, etc.
Reasons for explosion protection
Explosive substances: Some flammable substances are produced in many production sites. Explosive substances exist in about two-thirds of underground coal mines; in the chemical industry, explosive substances exist in more than 80% of the production workshop area. Oxygen: Oxygen in the air is everywhere. Ignition source: A large number of electrical instruments are used in the production process, and various frictional electric sparks, mechanical wear sparks, static sparks, high temperature, etc. are inevitable, especially when instrumentation and electrical failures occur. 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 an explosion source, an explosion will occur. Therefore, it is necessary to take explosion protection.
Hazard division
Dangerous gas dust
| Explosive substance | Area definition | Chinese standard | North American Standard |
| Gas (CLASS Ⅰ) | Under normal circumstances, places where explosive gas mixtures exist continuously or for a long time | 0 Area | Div.1 |
| Places where explosive gas mixtures may occur under normal circumstances | 1 Area | ||
| Under normal circumstances, explosive gas mixtures are unlikely to occur, but only in abnormal circumstances, occasionally or in a short time. | 2 Area | Div.2 | |
| Dust or fiber (CLASS Ⅱ/Ⅲ) | Under normal circumstances, explosive dust or the mixture of combustible fiber and air may be continuous, frequently appearing in a short time or existing for a long time | 10 Area | Div.1 |
| Under normal conditions, explosive dust or a mixture of combustible fibers and air cannot appear, only in abnormal situations, occasionally or in a short time. | 11 Area | Div.2 |
Applicability of explosion-proof methods to hazardous locations
| Serial number | Explosion-proof type | Code | National standard | Explosion-proof measures | Applicable Area |
| 1 | Flameproof | d | GB3836.2 | Isolate existing ignition sources | Zone1,Zone2 |
| 2 | Increased safety | e | GB3836.3 | Try to prevent ignition sources | Zone1,Zone2 |
| 3 | Intrinsically safe | ia | GB3836.4 | Limit the energy of the ignition source | Zone0-2 |
| Intrinsically safe | ib | GB3836.4 | Limit the energy of the ignition source | Zone1,Zone2 | |
| 4 | Positive pressure | p | GB3836.5 | Hazardous substances are separated from ignition sources | Zone1,Zone2 |
| 5 | Oil-filled | o | GB3836.6 | Hazardous substances are separated from ignition sources | Zone1,Zone2 |
| 6 | Sand-filled | q | GB3836.7 | Hazardous substances are separated from ignition sources | Zone1,Zone2 |
| 7 | Non-sparking type | n | GB3836.8 | Try to prevent ignition sources | Zone2 |
| 8 | Encapsulated | m | GB3836.9 | Try to prevent ignition sources | Zone1,Zone2 |
| 9 | Airtight | h | GB3836.10 | Try to prevent ignition sources | Zone1,Zone2 |
Dangerous gas
Classification
According to the minimum spark energy that may detonate, my country, Europe, and most countries and regions in the world divide explosive gases into four hazard levels, as shown in the following table:
| Working condition category | Gas classification | Representative gas | Minimum spark energy |
| Underground | Ⅰ | Methane | 0.280mJ |
| Factory outside the mine | ⅡA | Propane | 0.180mJ |
| ⅡB | Ethylene | 0.060mJ | |
| ⅡC | Hydrogen | 0.019mJ |
| Group Name | Representative gas or dust |
| A | Acetylene |
| B | Hydrogen |
| C | Ethylene |
| D | Propane |
| E | Metal dust |
| F | Coal dust |
| G | Grain dust |
Classification of gas temperature groups:
| Temperature group | Safe surface temperature | Common explosive gas |
| T1 | ≤ 450℃ | 46 kinds of hydrogen, acrylonitrile, etc. |
| T2 | ≤ 300℃ | 47 kinds of acetylene and ethylene |
| T3 | ≤ 200℃ | 36 types including gasoline and crotonaldehyde |
| T4 | ≤ 135℃ | 6 kinds of acetaldehyde, tetrafluoroethylene, etc. |
| T5 | ≤ 100℃ | Carbon disulfide |
| T6 | ≤ 85℃ | Ethyl nitrate and ethyl nitrite |
The meaning of Ex(ia)ⅡC T6:
| Logo content | Symbol | Meaning |
| Explosion-proof declaration | Ex | Comply with certain explosion-proof standards, such as my country's national standards |
| Explosion-proof method | ia | Adopt ia-level intrinsically safe explosion-proof method, can be installed in Area 0 |
| Gas category | ⅡC | It is allowed to involve explosive gas of IIC |
| Temperature group | T6 | The surface temperature of the instrument does not exceed 85℃ |
The meaning of Ex(ia)ⅡC:
| Logo content | Meaning | |
| Explosion-proof declaration | Ex | Compliance with European explosion-proof standards |
| Explosion-proof method | ia | Adopt ia-level intrinsically safe explosion-proof method, can be installed in Area 0 |
| Gas category | ⅡC | It is allowed to involve explosive gas of IIC |
Explosion-proof mark
The explosion-dangerous medium in the factory or mining area is scientifically classified and classified according to its ignition energy, minimum ignition temperature, and the time period of the on-site explosive hazardous gas to determine the explosion-proof mark and explosion-proof form of the on-site explosion-proof equipment.
Explosion-proof mark format:
Ex (ia) ⅡC T4
Explosion-proof mark Explosion-proof grade Gas group Temperature group
Explosion-proof grade description:
ia level:
Electrical equipment that cannot ignite explosive gas mixtures during normal operation, one failure and two failures.
When working normally, the safety factor is 2.0;
When a fault occurs, the safety factor is 1.5;
In the case of two failures, the safety factor is 1.0.
Note: Contacts with sparks must be equipped with flameproof enclosures, air-tight enclosures or double the safety factor.
ib level:
Electrical equipment that cannot ignite explosive gas mixtures during normal operation and a malfunction.
In normal operation, the safety factor is 2.0; in case of a fault, the safety factor is 1.5.
During normal operation, spark-proof contacts must be protected by flameproof enclosures or airtight enclosures, and there are measures to self-display failures. The safety factor is 1.0 for a failure.
Motor explosion-proof grade
The motor explosion-proof grade consists of 3 parts
1) The division of safety levels for different electrical equipment in explosive gas areas (Zone 0, Zone 1, and Zone 2). For example, the selection of rotating motors is divided into flameproof type (code d), positive pressure type (p), increased safety type (e), non-sparking type (n)
2) The classification of explosive mixtures of gas or vapor is divided into three types: IIA, IIB, and IIC. These classifications are mainly based on the maximum test safety gap (MESG) or the minimum ignition current (MICR).
3) Division of temperature groups that ignite a certain medium. Mainly divided into T1－450℃<T, T2－300<T≤450℃, T3－200<T≤300℃, T4－135<T≤200℃, T5－100<T≤135, T6－85<T ≤100℃.