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 shell, a cover, a fastener, and a joystick or shaft that passes through the shell 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 the clearance between the motor end cap and the housing, the clearance between the shaft and the bearing cover, etc.) must prevent flames from passing through the gap when the flammable mixture inside the housing explodes. Outside of the housing, the width (L and L1 values), clearance (W) and surface roughness of the joint surface should meet the requirements of the explosion-proof standard.
(1) Repair of explosion-proof housing:
If there is a crack in the shell, it is recommended to replace it with a new one; if a small through 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 spot 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 diameter of the flameproof surface is less than 1mm locally and the depth is not greater than 1mm, no more than 3 per square centimeter 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 At 12.5mm, not more than 2 per square centimeter, or 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 flameproof surface is not less than two-thirds of that specified in GB 836.2, 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, repair can be carried out, but one of the following conditions is not allowed to be repaired: the defect within 5mm around the screw hole; the length of the flameproof face is less than 6mm Defects; corners of the flameproof surface; active flameproof joint surfaces; castings with loose phenomena on the flameproof surface; cracks on the flameproof surface.
Defect repair methods on flameproof surfaces: fusion welding; brazing, for example, brazing for steel and cast iron parts; adhesion of metal powders for adhesion of adhesives, such as repair with epoxy resin, requiring adhesive to parent metal Adhesion is good, the use of temperature in the range of -30 °C ~ +150 °C does not soften, do not shrink, no cracking.
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 inserting method to add metal, and then processed to the specified size.
e. For moving joints (such as shafts, levers, etc.) should be repaired by welding or brazing after grinding or inserting.
The general flameproof enclosure is composed of a shell, a cover, a fastener, and a joystick or shaft that passes through the shell 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 the clearance between the motor end cap and the housing, the clearance between the shaft and the bearing cover, etc.) must prevent flames from passing through the gap when the flammable mixture inside the housing explodes. Outside of the housing, the width (L and L1 values), clearance (W) and surface roughness of the joint surface should meet the requirements of the explosion-proof standard.
(1) Repair of explosion-proof housing:
If there is a crack in the shell, it is recommended to replace it with a new one; if a small through 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 spot 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 diameter of the flameproof surface is less than 1mm locally and the depth is not greater than 1mm, no more than 3 per square centimeter 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 At 12.5mm, not more than 2 per square centimeter, or 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 flameproof surface is not less than two-thirds of that specified in GB 836.2, 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, repair can be carried out, but one of the following conditions is not allowed to be repaired: the defect within 5mm around the screw hole; the length of the flameproof face is less than 6mm Defects; corners of the flameproof surface; active flameproof joint surfaces; castings with loose phenomena on the flameproof surface; cracks on the flameproof surface.
Defect repair methods on flameproof surfaces: fusion welding; brazing, for example, brazing for steel and cast iron parts; adhesion of metal powders for adhesion of adhesives, such as repair with epoxy resin, requiring adhesive to parent metal Adhesion is good, the use of temperature in the range of -30 °C ~ +150 °C does not soften, do not shrink, no cracking.
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 inserting method to add metal, and then processed to the specified size.
e. For moving joints (such as shafts, levers, etc.) should be repaired by welding or brazing after grinding or inserting.
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