Type px pressurizing; pressurization that reduces the classification within the pressurized enclosure from zone 1 to non-hazardous or group I to non-hazardous.
Type py pressurizing; pressurization that reduces the classification within the pressurized enclosure from zone 1 to zone 2.
Type pz pressurizing; pressurization that reduces the classification within the pressurized enclosure from zone 2 to non-hazardous.
Equipment must be designed and constructed so that it prevents ignition sources arising, even in the event of frequently occurring disturbances or equipment operating faults, which normally have to be taken into account.
Equipment parts must be designed and constructed so that their stated surface temperatures are not exceeded, even in the case of risks arising from abnormal situations anticipated by the manufacturer.
The protection of the Ex p motor is mainly based on the pressured and purged enclosure. The enclosure should be purged before starting and must be overpressured all the time during operation. The overpressure must be at least 50 Pa. If it falls under the trip limit, the electrical supply should be automatically switched off. The purging gas could be normal air, but it must be supplied from the safe area.
Due to overpressure, the inner part of the enclosure does not belong to the hazardous area, so the temperature limits of stator and rotor are the same as for a standard machine. The contributions of single fault condition must still be taken into account (e.g. the pressure can drop, if pressurized air supply from the network is lost). This means that all temperatures of the inner parts should be under T-class limit in normal operating condition.