Coal mine explosion-proof inspection standards

I. General provisions:

    1. In order to further implement the “Coal Mine Safety Regulations” and the standards and regulations on explosion-proof electrics, to improve the understanding of electromechanical workers on the performance of explosion-proof electrics, and to facilitate the mastery of the use of the standards in practical work, so as to strengthen the scientific management of explosion-proof electrics in underground coal mines, to improve the quality of maintenance, to eliminate the electrics failure, and to realize the safe operation of electric equipments, the “Rules” are formulated.

    2. All underground electrical equipment (including small electrical equipment) must be selected in accordance with the requirements of Articles 444 and 7 of the Coal Mine Safety Regulations.

    3. Full-time explosion-proof inspectors must be trained and tested by higher authorities and obtain a certificate of competency. Part-time explosion-proof inspectors must undergo mine-level training and examination and obtain a certificate of competency.

    4. Explosion-proof electrical equipment must be inspected by full-time explosion-proof inspectors before entering the well for its “product certification”, “explosion-proof certification”, “coal mine product safety mark” and safety performance; only after passing the inspection and issuing a certificate of conformity will it be allowed to enter the well. After passing the inspection and issuing the certificate of conformity, the equipment will be allowed to enter the well. Explosion-proof electrical products for industrial trial operation must have the “industrial test license” issued by the quality supervision and inspection department, and the safety measures formulated by the using unit will be examined and agreed by the vice general manager of mine mechanical and electrical, or else they will not be allowed to go down the well.

    5. Downhole explosion-proof electrical equipment to change the rated value of the use and technical transformation, must be authorized by the state mining product quality supervision and inspection departments.

    6. Underground explosion-proof electrical equipment operation, maintenance and repair work, must meet the technical requirements of explosion-proof performance. Explosion-proof performance is damaged electrical equipment, must be immediately dealt with or replaced, is strictly prohibited to continue to use.

    7. The maintenance of the explosion-proof shell shall be carried out in accordance with the “Coal Mine Explosion-proof Electrical Equipment Shell Repair Regulations”, and must be repaired by the unit or manufacturer that has obtained the qualification of explosion-proof inspection.

    8. Strengthen the inspection of explosion-proof electrical performance in use underground:

    (1) Maintenance workers (part-time explosion-proof inspectors) of explosion-proof electrics under their jurisdiction shall inspect the explosion-proof electrics at least once per shift.

    (2) A full-time explosion-proof inspector inspects the explosion-proof electrics of a high-gas mine or a high-gas area of a low-gas mine at least twice a week. The explosion-proof electrics of low-gas mines are inspected once a week.

    (3) Full-time and part-time explosion-proof inspector staffing must meet the needs of explosion-proof inspection work.

  II. General provisions:

    1. Explosion-proof electrical equipment (including small electrical appliances), the use of cable voltage level shall not be higher than its nominal voltage level, otherwise it is considered to be lost.

    2. If the 9# terminal of the explosion-proof magnetic switch used in high gas, coal and gas prominent mines is grounded or if the explosion-proof shell is electrified for some reason, it is regarded as loss of explosion.

    3. The use of switches to control the incoming and outgoing power lines of the incoming and outgoing devices is considered to be a loss of explosives (except for access to the leakage detection relay and the power supply of the control circuit).

4. All explosion-proof electrical equipment should be managed according to the explosion-proof requirements no matter where it is used underground. 

III, the explosion-proof shell must have a clear explosion-proof signs, coal safety signs. One of the following conditions for the loss of explosion:

    1. The shell has cracks, open welding, serious deformation (the deformation length is more than 50mm, and the depth of convexity and concavity is more than 5mm).

    2. Explosion-proof shell inside and outside the rust skin off (rust skin thickness of 0.2mm and above).

    3. The transparent plate of the observation hole (window) of the explosion-proof chamber (cavity) is loose, broken or using ordinary glass.

    4. explosion-proof equipment explosion-proof cavity directly through, remove the explosion-proof equipment junction box within the explosion-proof insulating seat.

5. Locking device is incomplete, deformation damage can not play the role of locking.

IV, the explosion-proof surface should be kept clean, intact, need to have anti-rust measures.

    1. The structural parameters of the explosion-proof joint surface shall comply with the following provisions, otherwise it is regarded as a loss of explosion:

    (1) electrical equipment stationary part of the explosion-proof joint surface, joystick and shaft and bearing shaft explosion-proof joint surface and the corresponding shell volume corresponding to the maximum clearance must be consistent with the provisions of Table I. The minimum effective length of the fast-acting door type is not 25mm. Quick-action door type explosion-proof joint surface of the minimum effective length of not less than 25mm.

    (2) The average roughness of the explosion-proof joint surface shall not be higher than 6.3μm.

    (3) no rust on the surface of the explosion isolation (rubbed with cotton gauze, there are still rust spots for rust, while only leaving the cloud shadow, not counted as rust).

    (4) Bolted and fastened blast-isolating surfaces:

    ① Bolts and spring washers must be complete and tight (tightness to flatten the washer is qualified).

    ② spring washer specifications shall be compatible with the bolt, (occasionally individual spring washer breaks or loss of elasticity, check the explosion-proof clearance, if not over the limit, replace the qualified spring washer is not a loss of explosion).

    ③ Bolts or screw holes can not slip buckle (except for the replacement of long bolts of the same diameter and nut fastening).

    (iv) For bolts and impermeable screw holes, the axial length of the remaining threads on the bolts and screw holes after tightening should be greater than 1.5 times the thickness of the spring washers; the thickness around and at the bottom of the screw holes should be greater than 3mm.

    ⑤ The specifications of bolts and nuts in the same part should be the same, and the depth of the steel fastening bolts screwed into the nuts should not be less than the diameter of the bolts.

    (vi) The length of the countersunk hole steel fastening bolt into the screw hole should be greater than the diameter of the bolt, cast iron, copper, aluminum parts not less than 1.5 times the diameter of the bolt; if the depth of the screw hole is not enough, it must be on the full hole.

    (vii) The motor junction box cover must not be reversed.

    2. On the explosion-isolating surface, defects within the specified length and the shortest effective length from the edge of the screw hole to the edge of the explosion-isolating surface shall not exceed the following provisions:

    (1) For the local appearance of the diameter is not greater than 1mm; the depth is not greater than 2mm of sand holes, in the 40, 25, 15mm explosion-proof surface, not more than 2 per square centimeter.

    (2) The mechanical wound produced by chance, its width and depth is not greater than 0.5mm, the effective length of the remaining non-injury blasting surface is not less than 2/3 of the specified length.

    (3) explosion-proof surface is not allowed to paint (found in the paint when checking the gap does not exceed the provisions of the joint length without paint in the joint length is not less than the length of the provisions of the 2/3 is not a loss of explosion).

    3. Explosion-proof motor

    (1) The explosion-proof joint surface of the motor shaft and the shaft hole should not produce friction under normal working condition. When the cylindrical explosion-proof joint surface is used, the minimum unilateral clearance between the shaft and the shaft hole shall be not less than 0.075mm.

    (2) Rolling bearing structure, the maximum unilateral clearance between the shaft and the shaft hole shall be not more than 2/3 of the value specified in Table I. v. Cable introduction device:

    The cable introduction device shall be complete, complete, tight and well sealed, and one of the following conditions shall be a failure to explode:

    1. The inner diameter of the seal is larger than the outer diameter of the cable by more than 1mm.

    2. The difference between the inner diameter of the inlet nozzle and the outer diameter of the sealing ring exceeds the value specified in Table II.

    3. The width of the sealing ring is less than 0.7 times the outer diameter of the cable, or the minimum width is less than 10mm.

    4. The thickness of the sealing ring is less than 0.3 times the outer diameter of the cable (except for cables of 70 square millimeters and above), or the minimum thickness is less than 4mm.

    5. Seals with multiple cables threaded into a single hole.

    6. Cut the sealing ring over the cable.

    7. Seal ring hardness does not meet the Sauer’s hardness 45 degrees – 55 degrees, aging (cracking, sticky, hardening, softening, pulverization, discoloration and other phenomena) loss of elasticity, permanent deformation, the effective size of the fit gap does not meet the requirements of the sealing role.

    8. The sealing ring is not completely on the cable sheath (or armored cable lead skin).

    9. There are other wrappings between the sealing ring and the cable sheath (or lead skin of the armored cable); there are fillers between the sealing ring and the feeding nozzle.

   10. Multiple seals are used in one inlet nozzle.

   11. Cable introduction devices with threads, with thread engagement of less than 5 fasteners, with threaded portion less than 8 mm in length and less than 6 fasteners threaded.

   12. Thread accuracy is less than grade 3 and pitch is less than 0.7mm.

   13. The unused feeder nozzle lacks a sealing ring or baffle; or the baffle is placed inside the sealing ring; the diameter of the baffle is less than the inner diameter of the feeder nozzle by more than 2mm; the thickness of the baffle is less than 2mm or the thickness of the baffle is less than 3mm when the diameter of the baffle is 110mm and above (all the baffles should be zinc-plated).

   14. In the use of the spiral feeder nozzle lack of metal ring; metal ring and feeder nozzle mismatch. (Unused feeder nozzles can be used without metal rings).

   15. After the inlet nozzle is pressed, there is no margin or the inner edge of the inlet nozzle cannot press the sealing ring tightly; the sealing ring end face is not in good contact with the wall; or the sealing ring can be movable.

   16. Pressure plate type wire feed nozzle lack of compression bolt or compression bolt is not tightened, with a hand can make the wire feed nozzle obvious shaking.

   17. Nut-type wire feeder nozzles that cannot be tightened in place due to messy buckling, rusting, etc. or where the thumb, forefinger, and middle finger of one hand are used to make the compression nut advance more than half a turn in the direction of screwing in.

   18 cable at the inlet nozzle that is pushed with one hand in the direction of the cable inlet.

   19. When the high-voltage armored cable junction box uses insulating rubber, the insulating rubber is not filled above the three-forked mouth; the insulating rubber has cracks that can be relatively active.

VI. Connection of cables:

    A cable connection is considered to be out of burst if one of the following conditions applies:

    1. The cable is not connected with vulcanized hot patch.

    2. Cables (including communication, lighting, signaling, control cables) if the junction box with non-intrinsically safe equipment, do not use explosion-proof cable junction box (belonging to the intrinsically safe control of communication cables, should be used intrinsically safe junction box);

    3. Armored cable connection does not use junction box, the middle box is not filled with insulation filling material or filling is not strict leakage of the core line of the joints;

    4. The end of the cable is not connected to the installation of explosion-proof electrical equipment or explosion-proof components;

    5. Electrical equipment and cables with exposed conductors;

6. Rubber jacket, cross-linked polyethylene cable sheath damage exposed core (shielded cable exposed shield or intrinsically safe equipment connected to the cable exposed conductor except, but should be promptly repaired).

VII. Flame-proof plug-in device:

    1. The power supply side of the plug of the coal electric drill should be connected to the socket, the load measurement is connected to the plug, and the connection is reversed to be regarded as a loss of explosion.

    2. Splice device lack of preventing the sudden pull off the Xu move device, power supply voltage in the 660 volts – 1140 volts of the plug device lack of electrical interlocking device is considered to be out of explosion.

    3. Plug in the contact disconnect the moment of power failure, the shell of the maximum diameter of the burst surface difference w and the minimum effective length L, does not meet the provisions of Table III for the loss of explosion.

VIII. Lighting appliances:

    1. Explosion-proof safety type lamps and lanterns to change the pressure port to the Luo port for the loss of explosion.

    2. Explosion-proof lamps and lanterns can only be opened after the disconnection of the power supply transparent cover of the interlocking device failure for the failure of the explosion.

    3. Explosion-proof lamps and lanterns glass cover appears loose, cracked, broken one of the cases for the loss of explosion.

IX. Mining lamps:

   Mining lamps used underground must have the explosion-proof mark and the safety mark of coal mine mining products, and one of the following conditions is regarded as loss of explosion:

   1. Cracked lamp head, loose lamp head ring, cracked glass, poor lamp head seal, lamp lock failure.

   2. The lamp line is broken and exposed core wire, the lamp line introduction device is damaged sealing is not tight, the lamp line tampering.