Technical Update - IEC 60079-14 & Action to be taken on failure of Pressurization
What is IEC 60079-14?
This part of IEC 60079 contains the specific requirements for the design of electrical systems, selection, installation and the required initial inspection of electrical installations of Ex equipment in, or associated with, explosive atmospheres including requirements for documentation and personnel competency.
What does it tell us about Pressurization?
In addition to essential general information about hazardous area equipment selection, and the relationship between EPLs (equipment protection levels) and Zones, the standard has specific information pertaining to Ex p systems.
For example, Table 9 of IEC 60079-14 - "Determination of Type of Protection" describes which types of protection by pressurization are required to be suitable for different EPLs. Below is a small selection of the table highlighting the requirement for the "pxb" type of protection of EPL Gb (equipment suitable for IECEx Zone 1 areas).
| EPL | Enclosure contains equipment not meeting EPL Gc or EPL Dc requirements as applicable |
|---|---|
| Gb or Db | Type "pxb" |
| Gc or Dc | Type "pxb" or "pzc" |
IEC 60079-14 also provides detail on the action to be taken on failure of pressurization.
For this technical update, we will focus on the requirements for EPL Gb (equipment suitable for IECEx Zone 1 areas). Table 11 - "Summary of protection requirements for enclosures without an internal source of release" states that upon failure of pressurization of the pressurized enclosure, there must be an alarm and automatic switching-off of the power to internal equipment which is not otherwise suitably protected.
See below relevant section of table 11
| EPL requirement | Enclosure contains equipment NOT meeting EPL Gc or Dc requirements, as applicable to the hazard, without pressurizationb |
|---|---|
| Gb or Dc | Alarm and automatic switching-off (Apply 6.18.3.2.3 and 6.18.3.2.2) |
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