I. Requirements of electrical equipment for underground working conditions in coal mines

　　1. The underground environment is humid, and some places have water showers. Therefore, electrical equipment is required to be drip-proof (splashing). Flameproof enclosures and explosion-proof joints are required to prevent corrosion. Electrical insulating materials are required to be resistant to moisture. In addition, the downhole temperature is high, so the heat and moisture test of the insulation performance of the mining electrical equipment should also be conducted.

　　2. Underground mines often have coal, rock falling, gangs, and pulling, hanging, bumping, and bumping of sports equipment, which can easily damage the equipment. Therefore, electrical equipment is required to have a strong casing.

　　3, underground mining face often moves, electrical equipment will also move, so the requirements of electrical equipment selection and structure should be easy to carry.

　　4. The downhole work is heavy and the load changes greatly. Therefore, it is required that the electrical equipment run reliably and have a certain overload capacity.

　　5. The underground space is narrow and the lighting is insufficient. Therefore, it is required that the electrical equipment be small in size, simple in operation, and convenient in maintenance.

　　6. Explosive mixtures such as biogas and coal dust exist underground, so electrical equipment used in explosive environments is required to be explosion-proof.

　　Second, the type of explosion-proof electrical equipment

　　In order to standardize the design and manufacture of explosion-proof electrical equipment and to facilitate maintenance, use and maintenance, China has formulated a complete national standard for explosion-proof electrical equipment. The standard number is GB3836.

　　First, the form of explosion-proof electrical equipment

　　1. Flameproof electrical equipment The electrical equipment with flameproof enclosure is called flameproof electrical equipment. Features are anti-explosive and non-passivating. The sign is "d". Standard number GB3836.2---83.

　　2. The normal operating conditions of the increased safety electrical equipment (which means that the equipment meets the requirements of the design specification in electrical and mechanical conditions and is used within the limits specified by the manufacturer) will not generate arcs, sparks or high temperatures that may ignite the explosive mixture. The electrical equipment, known as increased safety electrical equipment. The symbol is "e". Standard number GB3836.3---83.

　　3. Intrinsically safe electrical equipment All circuits are intrinsically safe circuits and refer to the circuits in which the prescribed explosive mixture can not be ignited under the specified test conditions under the conditions of normal operation or specified fault conditions. This kind of electrical equipment is called intrinsically safe electrical equipment. The symbol is "i(ia,ib)". Standard number GB3836.4---83.

　　4. Positive pressure type electrical equipment Electrical equipment with positive pressure enclosure is called positive pressure type equipment. The positive pressure housing is directed to the protective gas introduced into the housing, keeping the pressure of the internal protective gas higher than the pressure of the surrounding explosive environment to prevent the external explosive mixture from entering the housing inside the housing. The sign is "P". Standard number GB3836.5---87.

　　5. Oil-filled electrical equipment Electrical equipment that immerses all components or parts that may produce electrical sparks and overheating in oil so that they cannot ignite explosive mixtures above or on the outside of the enclosure is called a charged electrical device. The sign is "O". Standard number GB3836.6---87.

　　6. Sand-filled electrical equipment is filled with grit material inside the enclosure so that under the specified conditions, the arc generated within the enclosure, the propagating flame, the overheating temperature of the shell arm or grit material surface cannot ignite the electrical energy of the explosive mixture around the device. The equipment is called sand-filled electrical equipment. The sign is "q". Standard number GB3836.7---87.

　　7. Encapsulant type electrical equipment Encapsulating electrical equipment or components in encapsulants, such that the equipment that does not ignite the surrounding explosive mixture under normal operation and considered overload or failure is called encapsulated electrical equipment. The sign is "m". Standard number GB3836.

　　8. Non-spark type electrical equipment Under normal operating conditions, the surrounding explosive mixture will not be ignited, and electrical equipment that does not normally have a igniting effect will be referred to as a non-spark type electrical equipment. The sign is "n". Standard number GB3836.8---87.

　　9, airtight electrical equipment Air-tight enclosures with electrical equipment called airtight electrical equipment. The sign is "h".

　　10. Special-type electrical equipment that does not belong to the above-mentioned basic explosion-proof type or the combination of the above-mentioned basic explosion-proof type in structure, and adopts other special measures that have been fully tested and proves to have the ability to prevent ignition of explosive mixtures is called special type Electrical Equipment. The sign is "S".

　　11. The general type of mine is a kind of non-explosive equipment for coal mines. It is used in places where there is no risk of gas explosion. The basic requirement is that the foreign passengers are strong and closed to prevent direct contact and live parts from the outside, drip-proof, splash-proof and moisture-proof. Good performance, cable entry device. And can prevent the cable from twisting and unplugging, and the switch handle and door cover have interlocking devices. The symbol is "KY". Standard number GB12178----90.

　　Second, explosion-proof electrical equipment category

　　Explosion-proof electrical equipment is divided into two categories: Category I (explosion-proof electrical equipment for underground coal mines); Category II (explosion-proof electrical equipment for factories).

　　Third, special regulations for explosion-proof electrical equipment

　　1. Motor: The outer fan on the extended end of the motor shaft is provided with a protective cover to prevent coal and concrete from falling into the fan cover to generate heat or sparks and cause gas accidents. The ventilation holes of the fan are required to have a certain ability to prevent foreign objects from falling in, have sufficient mechanical strength, and must not be intertwined with each other. The spacing is not less than 1% of the fan diameter, and the minimum is not less than 1mm. The fan is plastic and its resistance is not less than 109. Europe, the fan is an aluminum alloy, magnesium content of not more than 0.5%, (increased safety protection class IP23, intrinsically safe protection class IP54).

　　IP20: I --- foreign object level, P---- waterproof level.

　　Foreign Object Level Abbreviation Definition

　　0 No protection

　　1 Protection greater than 50mm

　　2 Protection greater than 12mm

　　3 protection greater than 2.5mm

　　4 Protection greater than 1mm

　　5 Dust prevention

　　6 dust-tight

　　Waterproof grade Abbreviation Definition

　　0 No protection

　　1, anti-drip

　　2, 15 degrees anti-drip

　　3, anti-water spray

　　4, splash

　　5, spray water

　　6, against the waves and strong water

　　7, soaked in water

　　8, diving

　　2, switch and control

　　A. For DC contact switches, it is not allowed to make oil-immersed structures due to arc extinguishing difficulties. B, Class I AC contact switch, only when the rated voltage is higher than 1140V, when the levels are isolated and the volume of oil contained in each pole does not exceed 5L, it is allowed to make the oil-immersed structure. C. High-voltage oil circuit breakers used in underground coal mines use a breaking capacity of 50% of the actual capacity. It should be noted that due to the fact that the oil is easily carbonized during use, coupled with the effects of downhole moisture and coal dust, the use of oil-filled electrical equipment is seldom used. . D. For short-circuit protection and leakage protection actions, the mechanism cannot automatically recover. It must be manually restored. E. Magnetic starters and disconnectors are electrically and mechanically interlocked with contactors to prevent malfunction. F. If the operating handle is detachable, the structure should be ensured that the controller can be removed in the stop position.

　　3, lighting fixtures

　　A. The part of the transparent cover of the lighting fixture should have a protection net with a mesh of 50*50mm.

　　B. The transparent protective cover and the protective net can withstand the specified impact and thermal fusion tests.

　　C. The interlocking device of the transparent member should be opened after the power is turned off, or a warning sign that prohibits live opening of the cover is provided.

　　D, transparent parts are not allowed to make threaded structures (except Miner's lamp).

　　E. In order to prevent overheating of the internal parts of the lamp, a reflector or other heat insulation measures are applied between the light inlet cavity and the light source cavity.

　　4, explosion-proof electrical equipment

　　(1) Explosion resistance: 1. The function of the flameproof enclosure is to limit the explosion to a very small area within the enclosure. Therefore, the enclosure must withstand the pressure caused by the explosion. Any material that can withstand the explosion pressure can be made into a flameproof enclosure. Must have a certain structural strength. 2. The pressure generated by the gas explosion is 0.77 MPa (under clearance conditions). If there is no gap, the explosion pressure is 1 MPa. 3, the explosion-proof shell made of steel, cast steel, cast iron, copper, aluminum alloy, thermosetting plastics, glass, ceramics and so on. 4. The explosion-proof shell of the mining face is made of steel plate or cast steel. The non-digging face can be HT25-47 gray cast iron. The static volume of not more than 0.01L can be used for ceramics, the volume of not more than 2L can be plastic, and the handheld device shell. Can be made of aluminum alloy.

　　(2) Not explosive

　　1. The gap, denoted by the symbol “W”, refers to the distance between the opposite surfaces of the joint surface. Due to the unevenness, the gaps on the joint surface are not equal, so the category, level and volume of the explosion-proof equipment are The maximum clearance value is specified by the length of the coupling surface.

　　The role of the gap: A, can extinguish the flame produced by the explosion. B. Cooling temperature after explosion (cooling below 450°C). C. It can leak the pressure generated during the explosion.

　　2. The length of the flameproof joint surface, denoted by the symbol "L", is the shortest length from the inside of the flameproof surface to the outside through the joint surface. Also called effective length. It is determined by the net volume of the explosion-proof equipment.

　　The same effect as the first two gaps.

　　(3) Roughness, as long as it does not affect the width of the gap, can be processed slightly rough will not affect the performance of the storm, generally up to um6.3--- um3.2 can.

　　Fourth, the explosion of common explosion-proof equipment

　　1. Any explosion-resistant or non-explosive material that fails to meet the required requirements is lost.

　　2. The product has no certificate, no coal mine safety mark (MA), and no explosion-proof mark (Ex) is explosion.

　　3, the shell has a serious deformation (the length of the scar exceeds 50mm, the depth of the bump reaches 5mm is a serious deformation), the shell is welded, cracks are lost.

　　4. The rusted equipment is explosion (there is oxide layer falling off, the inside and outside of the shell are rusted, and the rusted cotton yarn on the joining surface cannot be removed; the arc extinguishing paint in the cavity is lost; the general anti-rust treatment is Electroplating, coating 204-1 rust-proof oil, phosphating, medical Vaseline coating, etc. Flameproof surfaces are not allowed to be painted, butter, engine oil, etc., otherwise it is lost.

　　The criteria for rust or injury on explosion-proof surfaces are as follows: A. Small pinholes shall not exceed 5 in 1 cm 2 , depth shall not exceed 1 mm, and diameter shall not exceed 0.5 mm. B. The length and width of the flaw do not exceed 0.5 mm, and the projection length does not exceed 50% of the length of the joint surface. C. The depth of individual scars does not exceed 1 mm, and no injury distance is not less than the specified joint length.

　　5, interlocking device is not complete, deformation is not a locking effect for the loss of the explosion, the switch inside the power supply side have a dangerous card, otherwise it is also lost.

　　6. The transparent parts of the observation hole are loose, broken, unlined, and the mechanical strength is not enough.

　　7. The explosion-proof structure between the explosion-proof chamber is destroyed by explosion.

　　8. Changes to the original design dimensions, resulting in unacceptable electrical clearances and creepage distances are due to explosion.

　　Clearance: The shortest spatial distance between two exposed conductors.

　　Creepage distance: The shortest distance between two exposed conductors along the surface of a solid insulating material.

　　9, plug reversed (required jack power supply, plug load) is lost.

　　10, high-voltage cable connector filling irrigation above the trigeminal, or else the explosion.

　　11, bolted joint surface, lack of bolts, nuts, spring mats for the loss of explosion, the elastic pad is not flat, loose bolts for the explosion, bolt or screw hole slip buckle also for the explosion.

　　12. The clearance between the outside of the seal ring and the wall of the seal is not more than 2mm. When the seal ring diameter is less than or equal to 20mm, the gap should be 1mm, when the seal ring diameter is less than or equal to 60mm, the gap should be 1.5mm.

　　13. The gap between the inside of the sealing ring and the outside of the cable sheath shall not exceed 1mm.

　　14, the width of the sealing ring should be 0.7 times the diameter of the cable jacket, the minimum width of not less than 10mm, the thickness of the sealing ring should be 0.3 times the diameter of the cable jacket, the minimum thickness of not less than 4mm.

　　15, a wiring device with a seal, a plurality of seal ring for the explosion, a seal ring into a plurality of cables, seals and cable jacket with other materials, the seal ring is incomplete explosion.

　　16. The oil must not be touched between the sealing ring and the cable sheath, otherwise it is a loss of explosion (the oil has a corrosive effect on the rubber).

　　17, the seal ring is not completely set on the cable for the explosion.

　　18, the hardness of the seal ring does not reach 45 °C -55 °C, rubber aging, cracking, loss of elastic, metamorphic deformation are lost.

　　19, idle wiring device must have a seal ring and baffle (baffle thickness of not less than 2mm), the baffle on the outside of the apron, and vice versa for the loss.

　　20. There is no allowance for the inlet nozzle, and the sealing ring can move inside, and none of the pressure is lost.

　　21. If the cable is easily twitched at the inlet nozzle, the amount of cable compression must not exceed 10% of the cable diameter. Do not flatten the cable. If it does not, the cable will fail.

　　22, nut type disorderly buckled, unscrewed, silk rusted are all unexploded.

　　23, nut type with one hand is the buckle can be screwed more than half of the deduction for the explosion.

　　24, nut type apron outside the metal ring, not on, or on the anti-explosive.

　　25. The unused bell mouth is first sealed on the upper rear baffle, and then the metal ring is finally tightened, otherwise it is lost.

　　26. Chicken paws: Cable connections without connection boxes (cold packs).

　　Sheep tail: The sheath of the cable does not extend into the junction box (telescope).

　　Ming joint: chicken paw joint without bandage insulation.