Zone classification for buried valve and above ground actuator

[ttv78]

Dear All,

I would like to have your view on the following on a buried valve as I could not find specific reference from IP 15 or API 505 :

1) a natural gas pipe line with buried valve but the actuator is above ground. The valve has leak source of flange however, is buried. Since the actuator has some instruments and is above ground above the valve, does it require classification. If so what zone 1 or 2 ?

2) if I locate the valve in a pit, then I understand it would be zone 1 inside the pit.

Please clarify.

With best regards,

Vijay

 

[DRWeig]

Again, ttv78, we can't make the call for you from here. You say you have a flange for a leak source -- what about the valve seal? Does this valve continuously bleed gas, or only if upset? Is it a modulating control valve? How permeable is the soil? How many hours per year do you expect to have a combustible atmosphere in the area around the electric actuator?

In spite of all those questions, I would be inclined to classify the area as if the soil were not there. You just have to decide if it would be zone 1 or 2 in an open field at the point of your instruments. That's my opinion only, do not use it to form your design.

Best to you,

Goober Dave

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