1. Definition and use
Explosion-proof box is a kind of closed container, which is used to encapsulate electrical equipment or components (such as switches, meters and terminals) in flammable and explosive environment, and block the contact between internal potential ignition sources (arcs, sparks or high-temperature surfaces) and external explosive gas/dust through structural design.
2. Core explosion-proof design
Flame proof (ex d)
Shell strength: cast iron, cast aluminum or stainless steel, with a wall thickness of ≥5mm, which can withstand internal explosion pressure (usually ≥1.5MPa).
Clearance of joint surface: The precision machining clearance of flange joint surface (usually 0.15-0.2mm) can cool the flame and block the explosion propagation.
Sealing protection
Static seal: silica gel/fluororubber sealing ring achieves IP66/IP67 protection level, and prevents the penetration of combustible media.
Dynamic sealing: The cable lead-in device adopts stuffing box or explosion-proof glen head, to ensure the tightness when the conductor penetrates.
Pressure release mechanism
The pressure relief valve is designed (some models) to release gas directionally in case of overpressure, so as to avoid shell rupture.
3. International standard requirements
Certification test: explosion pressure test (1.5 times the maximum pressure for 10 seconds without deformation) and thermal stability test (joint clearance change < 15% at high temperature) of IEC 60079 series or ATEX standard are required.
Temperature group: the surface temperature should be lower than the self-ignition point of ambient gas (for example, T6 group ≤85℃ is suitable for hydrogen environment).
4. Typical application scenarios
Electrical control cabinet of oil drilling platform
Sensor junction box in chemical plant
Power distribution device in dust environment (such as flour mill)
