Area Classification Dilemna

[nightfox1925]

I further got s situation in one of the projects wherein the existing area classification of a certain area our company is working on has it's extents based from PLANT BATTERY LIMITS. The project calls for an electrical cabinet to be mounted near a piperack. However, this particular area classification drawings indicates the entire piperack to be Class I Div 2 and extending approximately 5ft from the piperack edge in both sides. The area classification drawing is not scaled. We figured out the 5ft extent from the piperack edge based from a civil drawing since it exactly matches the process battery limits.

My concern is that the cabinet length is big that a small portion of it crosses Class I Div 2 if I were to based it from this area classification drawing. There are no pumps on that part and closed piping systems are running above it. There is a liquid hydrocarbon pipe running at an El+14'B.O.P. and at 8.12ft away horizontally but its a closed piping with no valves. I will double check and locate for any drains and whether this drains are normally closed and only being opened during a shutdown (in whioch case should not be considered a point of release).

If that part where my cabinet is located do not have any items substantially near to it as a potential release of ignitable elements, is this going to be a technically justified approach instead of using the Battery Limit based area classification which I feel is over-exagerated?

I was on the belief that area classication extent boundaries should be based from actual sources of release from equipment around our cabinet and do not have to be based from process battery limits. BTW, our cabinet dimension is 8'WD x 7'HT x 1-1/2'DP.

Your views and inputs are highly appreciated.

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[gepman]

Area classification limits are based upon the governing codes for that installation, in the US usually API or NFPA. I have also worked on beverage alcohol distilleries where the classification was governed by DISCUS (DIstilled Spirits Council of the United States). If your governing code calls for the entire piperack to be a classified area then that is what the experience or research of the codewriters indicates and you must follow it.

When I have no code that directly applies then I try to find the most applicable API or NFPA code which indicates how to set the classified area boundaries.

 

[nightfox1925]

Thanks gepman. The standard reference wherein the Plant's area classification guidlines were based upon is API RP500 and API RP505 and CEC Part I. However, I do not find any clause that dictates the use of process battery limits as a basis for hazardous area classification extents.

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[MxGxK]

The area classification diagrams in APIRP500 and NFPA497 appear to use the source of release to define the hazardous area.