Explosion proof distribution box standards and installation issues

Preamble

With the continuous development of industry, the chance of using explosion-proof distribution boxes is also rising.

Explosion-proof distribution boxes are mainly used in coal mines, fire stations, petroleum, petrochemical installations and textile and other flammable and explosive places. These places are more prone to protection accidents. So in the choice of power distribution box to pay more attention to the protection of the equipment.

Specific standards for explosion-proof distribution boxes

I. Explosion-proof distribution box general standards

Distribution box production technology indicators to meet the specifications and design requirements, and in accordance with the provisions of the product implementation standards to produce.

All components and technical parameters need to comply with the national standard GB7251 design requirements, sample production needs to be notified to the construction unit, supervision, construction unit of the relevant personnel acceptance before full production.

II. explosion-proof distribution box box body part

Distribution box adopts stainless steel box (stainless steel material is Baosteel 304 or above), the color is stainless steel color, the thickness of the box is not less than 4.0mm.

III. explosion-proof box components

Electrical components in the distribution box/cabinet should comply with the relevant provisions and should maintain their electrical clearance and creepage distance under normal use conditions; the exposed live conductors and terminals in the box, their electrical clearance and creepage distance or impact withstand voltage should be at least in line with the relevant provisions of the electrical components directly connected to them.

VI. explosion-proof distribution box group assembly line

Wiring all fasteners are used galvanized parts, the secondary wiring needs to use black wire, and add casing sequencing; box of measuring instruments in the conductor should be well enameled tin; layered distribution box wiring should be considered trunking in and out.

Switch terminals should be matched with the wire cross-section; wiring after component installation should be neatly arranged and tied into a bundle with nylon tape to be fastened behind the board.

Explosion-proof distribution box use process common taboos

I. Use of wood materials without fire-retardant treatment

Consequences: lighting explosion-proof distribution box (board) if made of wood in a humid and dusty place, easy to mold, leakage; in addition, the wooden box (board) does not go through the fire-retardant treatment, easy to cause a fire, is a safety hazard.

Measures: In order to ensure safe use, lighting explosion-proof distribution boxes (boards) are required not to be made of flammable materials. Even in dry, dust-free places, wooden explosion-proof distribution boxes (boards) should be flame retardant before use.

II. the power distribution box into the field did not do the inspection

Consequences: lighting explosion-proof distribution box (board) without inspection, after installation, often found on its second floor without special grounding bolts, small cross-section of the protective grounding wire, there are electrical appliances that can be opened door and bare copper flexible wire of the metal frame is not a reliable connection, wires and electrical appliances are not connected to a solid, there is the phenomenon of anti-loop. The screws and nuts do not require galvanized parts, and the wire diameter does not meet the requirements. There is no color-coded labeling and no card cabinet or electrical circuit diagrams. The layout and spacing of electrical appliances are not reasonable, and modifications to the delayed schedule will also affect quality.

Measures: first of all, in processing orders, to the manufacturers of technical requirements in line with the design and norms and standards, manufacturers to produce samples, inspection and reproduction after passing; products into the field, should be in strict accordance with the design, norms and standards of the requirements of the inspection and acceptance, to confirm that the installation after passing.

III. the installation is not solid elevation does not meet the requirements

Consequence: The installation elevation of the lighting explosion-proof distribution box (panel) does not comply with the regulations, the installation is not firm, and the box is not vertical. When installed in the dark, the edges around the panel are not close to the wall, affecting the use of the function, the view is not good.

Measures: The elevation should meet the design requirements. When the design is not specified, the height of the bottom edge of the lighting explosion-proof distribution box from the ground should be 1.5 m, and the height of the bottom edge of the lighting distribution board from the ground should be 1.8 m. The lighting explosion-proof distribution box (board) should be installed securely, and the permissible deviation of the installation perpendicularity should not be more than 3 mm, and there should not be any gaps around the explosion-proof distribution box when it is installed in the darkness, the panel edges around the panel should be close to the wall, and the contact parts of the box body and the buildings and structures should be coated with anti-corrosion paint. Anti-corrosion paint should be applied.

IV. the box line cross messy not bundled into a bundle

Consequences: the wiring in the lighting explosion-proof distribution box (board) is messy, and the second board in the box presses against the pipe opening, which affects the entry of wires into the box. If forced to squeeze in, the wire insulation will be damaged over time, easily resulting in a short circuit. And make the maintenance inconvenience, affect the view.

Measures: lighting explosion-proof distribution box using metal boxes, should be done to prevent rust and corrosion treatment; box outlet holes can not be opened with welding, a pipe a hole, threading should be protected before the metal box holes; lines are neatly arranged, into the box piping position is reasonably arranged. Don’t let the second floor board to the pipe pressure too tight. The wires in the box should be laid in a straight line around the box, and neatly bundled into bundles.

V. No N, PE busbar in the electrical box

Consequence: N and PE busbars are not set in the lighting explosion-proof distribution box (board), which cannot ensure the safe operation of the line.

Measures: Lighting explosion-proof distribution box (board) are set up in the zero line (N line) and protective earthing line (PE line) bus, zero line and protective earthing line should be connected to the bus, not spliced, and numbered.

VI. Incorrectly wired screw fuses installed

Consequence: The screw fuse installed in the lighting explosion-proof distribution box (board) is not connected correctly, and the power cord is connected to the threaded terminal, which affects the replacement of the fuse core. And improper operation can easily lead to electric shock accidents.

Measures: To ensure safety, the power line of the screw fuse installed in the lighting explosion-proof distribution box (board) should be connected to the terminal of the center contact, and the load line should be connected to the threaded terminal.

VII. the protection line is not in place line diameter does not meet the requirements

Consequences: lighting explosion-proof distribution box (board) protection line is not arranged from the terminal, but by the box frame in series, the wire diameter is not set according to the requirements, explosion-proof distribution box door voltage over the safety of the device does not have a protective ground, easy to occur safety accidents.

Measures: according to the specification requirements, lighting explosion-proof distribution box (board) should be set up within the protective ground bus, bus should be connected to the protective ground; the cross-sectional area of the protective ground wire should not be less than the cross-sectional area from the power supply to the largest lead of the electrical appliances; but it should also be selected in accordance with the relevant provisions; explosion-proof distribution box (board) should be firmly and well grounded, there must be a locking device; 50V or more than the opening door of the electrical equipment, the movable panels should be connected with the grounded Good metal frame with bare copper flexible wire reliable connection; bare copper wire cross-sectional area should also be selected in accordance with the provisions; wall thickness of less than 2.5 mm metal box and box, should not be used as a pipeline cross-earthing line and electrical appliances to protect the grounding line of the pressure contact point.

VIII. Circuit name not labeled on brake

Consequence: The brake in the lighting explosion-proof distribution box (board) is not labeled with the name of the circuit, which brings inconvenience to the use and maintenance.

Measures: Generally, according to the requirements of codes and standards, the door of the lighting explosion-proof distribution box (board) should be affixed with a circuit system diagram, and the name of the circuit should be labeled on the brake, especially when there are AC, DC or different levels of power supply in the lighting explosion-proof distribution box (board), it should be labeled clearly.