Definition of explosion-proof grade
The explosion-proof grade of explosion-proof electrical equipment is divided according to the type of equipment used, the temperature group of explosive gas mixture, and the explosion-proof type of explosion-proof electrical equipment.
Explosion-proof electrical equipment is divided into two categories: Class I is electrical equipment used in underground coal mines; II is electrical equipment used in places other than mines, according to Zui Large Test Safety Clearance (MESG) or Zui Small Ignition Current (MICR), II Electrical equipment is divided into three categories: IIA, IIB, and IIC.
The above four categories are mainly based on the small spark energy that may be detonated under different working conditions. In China and Europe and most countries and regions in the world, the explosive gas is divided into four dangerous levels. The specific differences are as follows:
Group comparison
Secondly, according to the difference of the ignition temperature of the explosive gas mixture, the group is divided into six types: T1, T2, T3, T4, T5 and T6. The ignition temperature is represented by t(°C), and the ignition temperature of each group is :
T1 is: 450 ° C
T2 is: 300 ° C
T3 is: 200 ° C
T4 is: 135 ° C
T5 is: 100 ° C
T6 is: 85 ° C
Again, for different purposes, the explosion-proof type of explosion-proof electrical is different, the type of the main points are: 1, explosion-proof type, marked as d;
2. Increased safety type, marked as e;
3. Positive pressure type, marked as P;
4, intrinsically safe type, the logo is i,
5, oil-filled type, the mark is o;
6, sand filling type, the mark is q;
7, no spark type, the sign is n;
8, the sealing type, the mark is m;
9, airtight type, marked as h.
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Example
: The explosion-proof mark is dIIBT4, which means: the type of explosion-proof electrical products is explosion-proof type, which is the class IIB (class) used in Class II places, and the ignition temperature of explosive gas is T4.
Basic principle of explosion protection
Explosion concept
An explosion is a sudden change from a state, through physical or chemical changes, to another state, and the release of enormous energy. The energy released by the sharp speed will cause the surrounding objects to be subjected to violent impact and damage.
The three conditions that an explosion must have:
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.
Why should explosion protection
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, more than 80% of the production workshops have explosive substances. Oxygen: Oxygen in the air is ubiquitous. Ignition source: A large number of electrical instruments are used in the production process. Various kinds of friction sparks, mechanical wear sparks, static sparks, high temperature, etc. are inevitable, especially when the instrument or electrical fails.
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.
Principle of explosion-proof instrument
Hazardous location risk classification:
Explosive Substances Area Defines Chinese Standard North American Standard
Zone 0: Div.1 Gas (CLASS I) A place where explosive gas mixtures are present continuously or for long periods of time under normal conditions.
Zone 1: Zone 1 where explosive gas mixtures may occur under normal conditions
Zone 2: Div.2 Under normal circumstances, an explosive gas mixture is unlikely to occur, only in an abnormal situation, occasionally or in a short period of time.
Zone 10 Div.1: Dust or fiber (CLASS II/III) Under normal conditions, explosive dust or a mixture of combustible fiber and air may be continuous, frequently appearing in a short time or in a place that exists for a long time.
Zone 11 Div. 2: Under normal circumstances, explosive dust or a mixture of combustible fiber and air cannot occur, only in an abnormal situation, occasionally or in a short time.
Applicability of explosion-proof methods to hazardous locations:
Serial number explosion-proof type code national standard explosion-proof measures applicable area
1 Explosion-proof type d GB3836.2 Isolation of existing ignition source Zone1, Zone2
2 Increased safety type e GB3836.3 Try to prevent ignition source Zone1, Zone2
3 Intrinsic safety type ia GB3836.4 Limiting the energy of the ignition source Zone0-2
Intrinsically safe ib GB3836.4 limits the energy of the ignition source Zone1, Zone2
4 Positive pressure type p GB3836.5 Hazardous substance separated from ignition source Zone1, Zone2
5 Oil-filled type o GB3836.6 Hazardous substance separated from ignition source Zone1, Zone2
6 Sand-filled type q GB3836.7 Hazardous substance separated from ignition source Zone1, Zone2
7 non-sparking type n GB3836.8 Try to prevent ignition source Zone2
8 encapsulation type m GB3836.9 Try to prevent ignition source Zone1, Zone2
9 airtight type h GB3836.10 Try to prevent ignition source Zone1, Zone2
Applicability of explosion protection to hazardous locations:
Explosive hazardous gas classification
According to the small spark energy that may be detonated, China and Europe and most countries and regions in the world divide explosive gas into four hazard levels, as shown in the following table:
Working condition category gas classification representative gas zui small detonation spark energy
Mine I methane 0.280mJ
Factory outside the mine IIA propane 0.180mJ
IIB ethylene 0.060mJ
IIC hydrogen 0.019mJ
The United States and Canada first divide the explosive objects scattered in the air into three CLASS categories: CLASS I gas and vapor; CLASS II dust; CLASS III fiber. Then divide the gas and dust into Groups:
Group name representative gas or dust
A acetylene
B hydrogen
C ethylene
D propane
E metal dust
F coal dust
G grain dust
Gas temperature group division:
Temperature group, safe object surface temperature, common explosive gas
T1 ≤ 450 °C 46 kinds of hydrogen, acrylonitrile, etc.
T2 ≤ 300 °C 47 kinds of acetylene, ethylene, etc.
T3 ≤ 200 °C Gasoline, crotonaldehyde and other 36 kinds
T4 ≤ 135 °C 6 kinds of acetaldehyde, tetrafluoroethylene, etc.
T5 ≤ 100 °C carbon disulfide
Instrument explosion-proof mark
The meaning of Ex(ia)IIC T6:
Symbol content symbol meaning
Explosion-proof statement Ex meets certain explosion-proof standards, such as China's national standards
Explosion-proof mode ia is installed in zone 0 with ia-level intrinsically safe explosion-proof method
Gas category IIC is allowed to involve Class IIC explosive gases
Temperature group T6 meter surface temperature does not exceed 85 ° C
The meaning of Ex(ia)IIC
Symbol content symbol meaning
Explosion-proof statement Ex meets European explosion-proof standards
Explosion-proof mode ia is installed in zone 0 with ia-level intrinsically safe explosion-proof method
Gas category IIC is allowed to involve Class IIC explosive gases
: Note: There is no temperature group item in this mark, indicating that the meter is not in direct contact with explosive gas.
Explosion-proof term:
Explosion-proof terms and standards
Safety barrier safety parameter definition:
*8226; Safety barrier zui high allowable voltage: Um
Ensure the intrinsic safety performance of the safety barrier's intrinsically safe end, allowing the zui high voltage that may be input to the non-intrinsically safe end
*8226; Safety barrier zui high open circuit voltage: Uoc
The voltage zui is large when the intrinsically safe end is open within the high allowable voltage range of zui
*8226; Safety grid Zui large short circuit current: Isc
Large value of current zui when the intrinsically safe terminal is short-circuited within the high allowable voltage range of zui
*8226; Safety barrier allows distributed capacitance: Ca
Intrinsically safe external capacitors are allowed under the intrinsic safety performance
*8226; Safety barrier allows distributed inductance: La
Insulate the intrinsic safety of the intrinsically safe end of the intrinsic safety
Explosion-proof mark format description:
The explosion hazardous medium of the factory or mining area shall be classified and classified according to its ignition energy, small ignition temperature and the time period of the presence of explosive gas at the site to determine the explosion-proof mark and explosion-proof form of the explosion-proof equipment on site.
Explosion-proof logo format:
Ex (ia) IIC T4
Explosion-proof mark explosion-proof grade gas group temperature group
Explosion-proof grade description:
Ia rating: Electrical equipment that does not ignite an explosive gas mixture during normal operation, one fault, and two faults.
In normal work, the safety factor is 2.0;
When a fault occurs, the safety factor is 1.5;
In the case of two faults, the safety factor is 1.0.
Note: Sparked contacts must be fitted with a flameproof enclosure, a hermetic enclosure or double the safety factor.
Ib level:
Electrical equipment that does not ignite an explosive gas mixture during normal operation and a fault.
In normal operation, the safety factor is 2.0; in the case of a fault, the safety factor is 1.5.
In normal operation, sparked contacts must have a time factor of 1.0.
　 Shi, a fault
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