Area Classification of Natural Gas Valve Manifold

[secrenannujeu]

Hi all,

working on a project with a client

I know NFP 497 says generally the area classification is usually a 15' radius from a natural gas vessel/ valve etc.

I did some digging and it said to determine the actual distance instead of using the 15' rule to refer to API 505

API 505 further refers to IEC 60079-10-1 to calculate the extent of the classification area.

Is this the correct way to approach this? I took a look at IEC 60079-10-1 and it does give a good methodology and determining the zone.

for those wondering, client asked me to do this since their space is a bit tight. they want to know if we can get the hazard zone less then 15'

 

[alchemon]

NFPA 497 says a lot of things. Depending on the valve or vessel type, 15' applies or doesn't. Look at the diagrams. It tells you the answers. I have never heard of digging much further than the NFPA 497 diagrams for hazardous area classification. Remember, NFPA 497 classifies electrical requirements operating within those areas. Can you reduce the hazardous area. Maybe, maybe not. If no, buy classified electric equipment.

 

[ProSafPlant1]

Yes, Area Classification is basically probabilistic and detailed calculations can be done to support a particular design, although it can be time-consuming...

I've used the methodology described (with examples) in "Classification of Hazardous Locations", A.W. Cox et al, IChemE 1990 to determine sizes of leak openings and their probabilities, and DNV PHAST to model leak concentration distances.