1. Cable Entry Device (Gland) Construction (4-Piece Set)
The explosion-proof gland is theonly legal passagebetween an explosion-proof enclosure and a cable. Standard construction:
| Component | Function | Key point |
|---|---|---|
| Compression nut | Compresses the sealing ring | Locks against loosening once fully tightened |
| Elastic sealing ring | Seals against the cable outer diameter | Interference fit between inner diameter and cable outer diameter |
| Metal washer | Protects the sealing ring / prevents pull-out | Cannot be omitted |
| Entry body + thread | Connects to the enclosure wall | G/M thread engagement ≥ 5 threads |
2. Sealing Ring Rules (One Hole, One Cable, One Seal)
- One cable per hole: each sealing ring takes a single cable; running multiple cables through one ring is an automatic fail.
- Size matching: The sealing ring's inner diameter must be an interference fit with the cable's outer diameter. Slitting the ring to enlarge the hole is a classic violation (a common shortcut on site that causes big problems).
- Material: Oil-resistant elastomer. Once it hardens with age, the entire ring must be replaced.
- Cable gland sizing: When the cable's outer diameter on site is smaller, you must switch to a matching sealing ring or use a reducing sealing ring. Wrapping with tape is not acceptable.
Step 3: Incoming Cable Installation — 5 Steps (from stripping to labeling)
- Step 1: Verify the box's entry thread matches the cable gland (G1/2, G3/4, G1). Engage at least 5 threads and tighten.
- Step 2: Feed the cable through. Check the cable's outer diameter against the sealing ring's inner diameter. Confirm the interference fit before tightening.
- Step 3: Tighten the compression nut symmetrically to the specified torque. Pull the cable by hand —no movement.
- Step 4: Wiring inside the box: crimp the copper lug + tighten terminals. Torque per terminal specification. Maintain creepage distance.
- Step 5: Hang cable identification tags (circuit number, destination). Install a plug on every spare entry and log it.
Section 4: 4 Common Violations (items that will fail inspection)
① Spare entry left unplugged— a direct flame path; ② Sealing ring slit to fit a thicker cable— seal failure; ③ Using an ordinary PVC grommet instead of an explosion-proof cable gland— no explosion-proof rating at all; ④ Excess cable coiled inside the flameproof cavity— takes up volume and traps heat. After wiring, the cavity should be clean with no excess exposed conductors.
Section 5: Circuit Wiring Key Points (terminals and grounding)
Terminal: Per GB 3836.3 increased safety requirements, creepage distance and clearance must be increased. Terminal screws must be vibration-proof (spring washer / self-locking); stranded wire must be terminated with a ferrule.Grounding: The box has one internal and one external grounding terminal. The internal ground connects to the cable shield/PE. The external ground connects to the site grounding grid. Grounding continuity < 0.1Ω.
When reassembling a flameproof box after wiring,retighten the cover bolts diagonally one by one to the original torque. Apply a thin coat of anti-rust oil to the flameproof surface — get this step wrong and the entire box's explosion-proof integrity is lost.
FAQ FAQ
Can I drill extra cable entries on site if the explosion-proof box doesn't have enough?
No. Drilling destroys the flameproof enclosure structure and voids the certification immediately. If you need more entries, specify them at selection time based on the number of cables.
How tight should a cable gland be?
Tighten the compression nut untilthe cable cannot be moved by hand and the sealing ring is evenly compressed. If possible, follow the manufacturer's torque value. Better too tight than too loose, but do not crack the sealing ring.
What should I use to plug spare entries?
ApplyA threaded plug (blind plug) matching the entry thread, metal, engaging at least 5 threads. Rubber plugs or putty are not acceptable substitutes.
Can I add terminal blocks inside an explosion-proof box?
Can only addspecification terminals consistent with the certificationand leave sufficient creepage distance; adding components without authorization alters the certified structure and is not permitted.
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