Flameproof electrical equipment is explosion-proof and safe through explosion-proof enclosures. This type of explosion protection is defined in the corresponding international standard as "flameproof enclosure d". The general flameproof enclosure is composed of a housing cover fastener and a joystick or shaft that passes through the housing wall. Explosion-proof housings and covers are generally thicker and the materials must meet the requirements of the standard. They can withstand explosions inside the enclosure without damage. The fasteners (screws, nuts, etc.) of the fixed flameproof enclosure must have sufficient mechanical strength to withstand the above-mentioned explosion pressure without breaking and tensile deformation. Any joint or structural gap on the housing (eg clearance between shaft and cap of the motor end cap and housing clearance, etc.) must be able to prevent the flammable mixture inside the enclosure from exploding and the flame passing through the gap to the enclosure External, so the width of the joint (L and L1 values) clearance (W) and surface roughness should meet the requirements of explosion-proof standards.
(1) Repair of Flameproof Enclosure If there is a crack in the shell, it is recommended to replace it with a new one; if a small hole is found, it can be repaired by welding.
(2) Repair of Flameproof Joints
a. If there is slight corrosion on the flameproof joint surface, the rust can be wiped off with kerosene and a rag, and a thin layer of grease can be applied to prevent rust.
If the corrosion is serious, it is recommended to use rust remover to remove rust, and check the joint surface condition. If the flameproof gap value is greater than the drawings, but does not exceed the requirements of the explosion-proof standard, no repairs may be required.
b. If the local area of ​​the flameproof surface is less than 1mm in diameter and the depth is not more than 1mm, no more than 3 per cm2 when the length of the flameproof joint surface is not less than 25mm, or the length of the flameproof joint surface is not less than No more than 2 in the range of 12.5mm per square centimeter can also be without repair.
If the width and depth of the mechanical scratches on the flameproof surface do not exceed 0.5mm, the effective length of the remaining non-injured explosion-proof surface shall not be less than two-thirds of that specified in GB 3836.2, and it may be repaired without scratching. The protruding part should be flat.
c. If the pit or scratch exceeds the above-mentioned regulations on the flameproof joint surface, the repair can be carried out, but one of the following conditions is not allowed to be repaired:
1 defects in the range of 5.0mm around the screw hole;
2 defects with a flameproof surface length less than 6.0mm;
3 at the corner of the explosion-proof surface;
4 activities flameproof joint surface;
5 Castings with a loose phenomenon on the flameproof surface;
6 There is a crack on the flameproof surface.
Flameproof surface defect repair method:
1 welding;
2 Hard brazing, such as brazing for steel and cast iron parts;
3Adhesive metal powder replenishment, for example, using epoxy resin adhesive repair, the adhesive requires good adhesion to the parent metal, the use of temperature in the range of -30 °C ~ +150 °C does not soften, do not shrink, no cracking.
c.
d. If the flameproof joint surface is seriously damaged and the clearance exceeds the requirements of the explosion-proof standard, the damaged side can be flattened for the plane joint surface; for the cylindrical joint surface, one side can be slightly machined and the other side can be welded. Electroplating or nesting methods add metal and then process it to a specified size.
e. For moving joints (such as shafts, etc.) should be repaired by welding or brazing, or flattening or inserting.
(3) Repair of Screw Holes of Fasteners
Increase the size of the drill hole, re-tap, or weld the screw hole, flatten, re-drill and tap. However, when reaming or re-drilling, it must be ensured that the effective length of the flameproof joint surface (L1) and the thickness of the screw hole periphery are not less than 3mm.
(4) Fasteners are only allowed to be replaced with new ones of the same size and same grade.
(5) If the observation window on the flameproof enclosure is damaged, the transparent parts and seals are not allowed to be repaired, and they can be replaced with new ones.
(6) Repair of flameproof cable and conduit lead-in devices The elastic seals in the lead-in device should be replaced with spare parts of the same size and of the same quality.
(7) Repair of components in the flameproof enclosure The internal components of the explosion-proof enclosure are, in principle, repaired or repaired according to the repair method of the general product. However, it should be noted that the temperature of the external surface of the flameproof enclosure after repair does not exceed the requirements of the device's nameplate or explosion-proof standard.
(8) If the explosion-proof terminal blocks in the junction box are damaged, they should be replaced with the same spare parts as the original parts to ensure the flameproof performance between the cavity of the junction box and the cavity of the main body and the electrical clearance between different potential parts and Creepage distance.
(9) If the bushing through the explosion-proof enclosure is damaged, if it is a screw-type flameproof joint, replacement of the same spare part as the original part is recommended. If the individual bushings are cylindrical or conical joints, the bushings can be reconstructed from Teflon bars, but the geometry should be the same as the original part.
(10) If the outer fan or fan cover of the motor is damaged and needs to be replaced or repaired, attention should be paid that the distance between the fan and the fan guard baffle plate and fasteners should be no less than 1% of the fan diameter, resulting in a 1mm reduction, so as to avoid friction and collision sparks. . If the external fan is replaced, the magnesium content of the aluminum alloy fan can't exceed 6%. If it is replaced with a plastic fan, the explosion-proof inspection spare parts should be used. When repairing or replacing the fan guard, its degree of protection should meet the requirements of explosion-proof standards.
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