Why explosion-proof blowers must be complete units, not converted standard machines
In a classified area the certification covers the whole assembly. A standard blower with an explosion-proof motor is not the same thing.
Area classification is one of the few subjects where a partial solution is worse than no solution at all, because it creates the appearance of compliance without the substance.
What the certification actually covers
An explosion-proof rating applies to a complete assembly: housing materials, impeller clearances, shaft seal, terminal box, cable entry, surface temperature and the motor itself. Changing any element of that assembly can invalidate the rating of the whole.
This is why a standard blower fitted with an explosion-proof motor does not become an explosion-proof blower. The motor may be certified; the machine is not.
The ignition sources inside a blower
- Hot surfaces — compression heats the air and the housing; surface temperature must stay below the ignition temperature of the gas.
- Friction and impact — contact between impeller and housing can spark, which is why clearances and materials are specified.
- Static discharge — moving air and dust generate static, which has to be bonded and earthed.
- Electrical — terminal boxes, cable entries and motor design all have to suit the zone.
A contact-free side channel design removes the friction source by construction, which is one reason this machine type suits hazardous areas so well. But the housing materials, clearances and electrical elements still have to be specified and certified together.
What to tell us
For a hazardous area enquiry we need the zone, the gas group or dust group, and the temperature class. With those three items we can confirm which units are suitable and provide the certification detail your installation review will ask for.
If a supplier offers to certify a standard blower by swapping the motor, treat the offer as incomplete until they show you the certification for the assembly as supplied.