IEC explosive atmospheres & EPLs

[SolarPrestige]

I am reading IEC 60079.14 : 2007 (ed 4.0. Yes I know there is edition 5 (2013) released and some corrections in 2016.

What I want to understand, is edition 4 (2007) the version where equipment protection levels (EPLs) were first introduced? This is for my understanding. The plant I work at is designed to 1990's standards, so the Ex-area equipment is rated for a zone, mostly zone 2.

Do other people find the EPL method easy to work with? What was the main reason for introducing this?

 

[ScottyUK]

IEC 60069-14 introduced EPL's in the 2007 revision, although it appeared in the UK under the 2008 revision of BS EN 60079-14.

Personally I think the old system was simpler to understand, and the two aren't mutually exclusive. The use of EPL's is risk assessment based, and allows consideration of the consequences of an ignition as well as the probability of an ignition.

...

In the past, the equipment selection standard has provided a solid link between the type of
protection for the equipment and the zone in which the equipment can be used. As noted
earlier, nowhere in the IEC system of explosion protection is there any account taken of the
potential consequences of an explosion, should it occur.

However, plant operators often make intuitive decisions on extending (or restricting) their
zones in order to compensate for this omission. A typical example is the installation of ‘zone 1
type’ navigation equipment in zone 2 areas of offshore oil production platforms, so that the
navigation equipment can remain functional even in the presence of a totally unexpected
prolonged gas release. In the other direction, it is reasonable for the owner of a remote, well
secured, small pumping station to drive the pump with a ‘zone 2 type’ motor, even in zone 1, if
the total amount of gas available to explode is small and the risk to life and property from
such an explosion can be discounted.

...

The introduction of EPL's also shifts the balance of responsibility onto the design engineer, especially where the engineer decides that a lesser level of protection is acceptable based on perceived risk, whereas prior to 2007 the standard was far more clear-cut and prescriptive in its requirements for equipment in each zone.

 

[SolarPrestige]

Thanks Scotty. That is a clear picture of what the change means.