A breather is fitted to the enclosure to allow release of the flammable gases produced during arc quenching, preventing the build-up of these gases in the space above the oil. The breather also prevents the ingress of dust or moisture, which could contaminate the oil.
The minimum enclosure ingress protection in IP66.
A gauge is fitted to display the highest and lowest levels of the protective loquid, installed so that it can be easily read while the equipment is in service. At its lowest level, the minimum depth of oil above the arc/heat producing components must be not less than 25mm. A label shows the design maximum and minimum levels, taking into account level variations due to expansion/contraction of the oil over the entire ambient temperature range.
The free surface temperature of the protective liquid is required to be 25°C less than the minimum flashpoint for the protective liquid.
Internal and external fasteners, fluid level indicators and parts for filling and draining the protective liquid must be fitted with means to prevent them becoming loose in service.
Sealed enclosures are to be fitted with a pressure-relief device.
Non-sealed enclosures must have an expansion device incorporating a mechanism for automatic tripping of the electrical supply on detection of gas evolution form the protective liquid as a result of a fault within the enclosure. The trip mechanism may only be manually reset.
Only Ex “o” equipment having a complete certificate shall be installed in accordance with the manufacturer’s documentation.
Ex “o” enclosure or component that has only component certificate is not allowed to be installed in hazardous area unless it is part of an assembly of components in an equipment that has a full Ex certificate with the “X” and equipment label has full “Ex” marking including temperature class.
External field wiring connections shall be protected with the type of protection meeting the EPL requirement of the location.
