1. Difference 1: Enclosure Material and Strength (Withstands an Internal Explosion)
The enclosure of an explosion-proof distribution cabinet mustwithstand the pressure of an internal explosive mixture explosionwithout damage and without transmitting flame. A standard cabinet needs only 1.5–2 mm steel sheet, while an explosion-proof enclosure is tested per GB 3836.1 with an impact test and GB 3836.2 with an internal explosion pressure withstand test:
| Item | Standard distribution cabinet | Explosion-proof distribution cabinet |
|---|---|---|
| Enclosure material | Cold-rolled sheet 1.5–2 mm | Cast aluminum / 304 stainless steel / Q235 steel plate ≥ 4 mm |
| Strength verification | No explosion pressure requirement | Not damaged and no flame transmission under internal explosion |
| Impact test | Not required | No damage to flameproof surfaces after 1J (20J for portable) impact |
| hydrostatic test | Not required | Hydrostatic pressure test on every unit / batch sampling of flameproof enclosure |
2. Difference 2: Flameproof Joint (A feature ordinary cabinets simply don't have)
On an explosion-proof cabinet, the cover and the enclosure body meet atflameproof joints: a pair of precision-machined flange faces, clamped by bolts, with the gap held toa few tenths of a millimeter. When a flame passes through the narrow gap, it is quenched — this is the core of the flameproof design.
- Flanged joint: width and maximum gap per GB 3836.2 Table 1 (e.g., 25 mm width corresponds to a gap ≤ 0.5 mm).
- Threaded joint: cable entry devices must engage at least 5 threads.
- Maintenance red lines: flameproof surfaces must not be ground, must not be fitted with ordinary gaskets, and must not be painted with ordinary paint — only anti-rust oil may be applied.
3. Difference ③: Cable Entry Devices (cable glands vs. knockouts)
Ordinary cabinets use knockouts plus grommets for incoming cables; on an explosion-proof cabinet, every cable entry must use anexplosion-proof cable entry device (cable gland): a compression nut + elastomer seal + metal washer that completely seals the annular space between the cable outer diameter and the entry opening.Unused openings must be sealed with threaded plugs— miss plugging even one, and the explosion-proof protection fails.
4. Difference ④: Internal Components and Temperature Control (prevent ignition at the source)
For use inside explosion-proof cabinetsIncreased-safety or flameproof components: terminal creepage distance is increased, materials are self-extinguishing, and connections are vibration-proof and loosening-proof. The maximum surface temperature of the complete cabinet must stay below the temperature class of the surrounding gas (T1–T6), and high-dissipation components must be derated.
Do not try to save money by adding an explosion-proof enclosure to a standard cabinet, and do not install standard components inside an explosion-proof enclosure — the Ex certificate covers the complete cabinet structure of "enclosure + internal components." Any unauthorized modification voids the certificate and is non-compliant.
Section 5, Difference ⑤: Nameplate Markings and Factory Documentation (One nameplate tells you whether it is genuine)
The explosion-proof cabinet nameplate must be cast or permanently affixed with theEx marking (Ex d IIB T4 Gb), certificate number, and Ex certificate of conformity number, and the product falls under the CCC mandatory certification catalog; the documentation shipped with the unit includes a copy of the Ex certificate of conformity, the instruction manual, and the factory inspection report. A standard cabinet nameplate only shows model, voltage, and current. Zhejiang Golden Unicorn takes on explosion-proof distribution cabinet requirements throughjoint supply with an Ex-qualified manufacturerjoint supply with an Ex-qualified manufacturer, with complete documentation shipped with the unit.
FAQ FAQ
How much more does an explosion-proof distribution cabinet cost than a standard cabinet?
Typically 2–5 times. Cast aluminum or stainless steel enclosures, precision machining of flameproof surfaces, explosion-proof components, and certification costs are the main sources of the price difference.
Can a standard cabinet be used instead of an explosion-proof cabinet?
Absolutely not. Using uncertified equipment in a hazardous area is a serious violation, and an accident carries legal liability.
Can an explosion-proof cabinet be modified in-house?
NoThe explosion-proof certification applies to the complete cabinet structure. Any modification — swapping components, cutting openings, or changing cable glands — voids the certificate.
Can a standard distribution cabinet be used in Zone 2?
No. Zone 2 requires at minimum Ex n (non-sparking) or higher. A standard cabinet does not meet any explosion-proof requirement.
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