No internal source of release #
The over-pressure within the enclosure is monitored by a pressure switch/sensor, and a flow-rate switch/sensor, located at the exhaust dust, is used to monitor the rate of flow of the safe gas through the enclosure. Loss of over-pressure or rate of flow will activate either an alarm or shutdown of the internal electrical components, the action taken being dependent on:
- The EPL requirement of the area in which the system is located;
- The type of equipment/components within the enclosure.
IEC 60079-14:2013, Table 18, specifies the action to be taken on loss of pressure as follows:
| EPL requirement | Enclosure contains equipment not meeting EPL ‘Gc’ requirements without pressurisation | Enclosure contains equipment meeting EPL ‘Gc’ requirements without pressurisation |
| ‘Gb’ | Alarm and switch off a | Alarm b |
| ‘Gc’ | Alarm b | No action |
a – If automatic switch-off would introduce a more dangerous condition, other precautionary measures should be taken, for example, duplication of protective gas supply.
b – If the alarm operates, immediate action should be taken to restore the integrity of the system.
With an internal source of release #
The action to be taken depends on the Zone, type of equipment and the type/severity of the release. (Details are beyond the scope of these notes).
