Gas Fired Genset - Area Class

[mpreisler]

I have a CAT gas fired generator in an enclosure which is located in a non-classified area. The question has come up whether the instrumentation and electrial devices inside the enclosure need to be Class 1, Div 2 rated due to the fact that the unit does have a fuel gas supply (150psig) to the engine. I would appreicate if anyone had experience with this type of situation if you could provide some insight.

Thanks,

 

[dicklaxt]

I believe this would be a good starting point,,,,,,,IMO the answer would be "no"



NFPA 497
Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
1997 Edition
3-3.1
Experience has shown that the release of ignitable mixtures from some operations and apparatus is so infrequent that area classification is not necessary. For example, it is not usually necessary to classify the following areas where combustible materials are processed, stored, or handled:
(a) Areas that have adequate ventilation, where combustible materials are contained within suitable, well-maintained, closed piping systems
(b) Areas that lack adequate ventilation, but where piping systems are without valves, fittings, flanges, and similar accessories that may be prone to leaks
(c) Areas where combustible materials are stored in suitable containers

3-3.3
Open flames and hot surfaces associated with the operation of certain equipment, such as boilers and fired heaters, provide inherent thermal ignition sources. Electrical classification is not appropriate in the immediate vicinity of these facilities. However, it is prudent to avoid installing electrical equipment that could be a primary ignition source for potential leak sources in pumps, valves, and so forth, or in waste product and fuel feed lines.

dick

 

[Gregg Harris]

I have a CAT gas fired generator in an enclosure which is located in a non-classified area. The question has come up whether the instrumentation and electrial devices inside the enclosure need to be Class 1, Div 2 rated due to the fact that the unit does have a fuel gas supply (150psig) to the engine. I would appreicate if anyone had experience with this type of situation if you could provide some insight.

Thanks,

Do you have any more information on this room such as mechanical ventilation, air changes per hour, pressure regulators, valves etc.? Is it a stand alone building. Are you sure it is 150 psig of gas being fed into the area? Natural or propane?

 

[copper chopper]

good ?

good ?

i am doing a dual generator set-up right now with diesil tanks under each gen and 2-6000 gallon tanks outside. it is in a seperate building on its own and it has air exchanges every 10 minutes.Nothing is done in an explosion proof manner.I used regular emt and steel set-screw fittings for it all.This tuesday we will be getting final inspection, if there is an issue I will post it.You have me worried now because this inspector is a pain in the butt.Also there are fire shut off solenoids on the incoming fuel lines.

 

[BPoindexter]

Diesel is different and does not require Classification as it does not produce vapors.

 

[bobgorno]

NFPA 37. Classification not required based on fuel or lube oil. Read the full text. This is only a paraphrase. There are other requirements.

 

[weressl]

I have a CAT gas fired generator in an enclosure which is located in a non-classified area. The question has come up whether the instrumentation and electrial devices inside the enclosure need to be Class 1, Div 2 rated due to the fact that the unit does have a fuel gas supply (150psig) to the engine. I would appreicate if anyone had experience with this type of situation if you could provide some insight.

Thanks,

Interesting. Gas supply at the user point is usually more like 0.5PSI for hosehold service and maybe in the 15-20PSI range in large commercial or industrial user's site.

If you have gas supply where all the pipe and instrument, control connections threaded threaded, rahter than flanged, you may get away without needing to classify the inside of the building.

Since the combustion engine also needs constinuous, fresh air supply, there must be some ventillation provision already available for the room. If you need to consdier leakeage possibility because of flanged connection, you can use the fresh air supply requirements of the combustion engine to force ventillate the room and reduce the Div. 2 classification to non-hazardous with the proper number of air exchanges per hour. (I belive it is 6.)

 

[Gregg Harris]

Interesting. Gas supply at the user point is usually more like 0.5PSI for hosehold service and maybe in the 15-20PSI range in large commercial or industrial user's site.

If you have gas supply where all the pipe and instrument, control connections threaded threaded, rahter than flanged, you may get away without needing to classify the inside of the building.

Since the combustion engine also needs constinuous, fresh air supply, there must be some ventillation provision already available for the room. If you need to consdier leakeage possibility because of flanged connection, you can use the fresh air supply requirements of the combustion engine to force ventillate the room and reduce the Div. 2 classification to non-hazardous with the proper number of air exchanges per hour. (I belive it is 6.)

This is why I posed my questions in the earlier post. It could vary well need to be classified.

 

[T.M.Haja Sahib]

It could vary well need to be classified.

Then perhaps the generator also can not be run due to lack of proper ventillation!

 

[iwire]

This is why I posed my questions in the earlier post. It could vary well need to be classified.

What do you believe could trigger the need?

We install many indoor gas fired gensets and I have never seen any require classified wiring methods.

If they did would not the genset also have to have a classified rating to use in a classified area?

 

[Gregg Harris]

What do you believe could trigger the need?

We install many indoor gas fired gensets and I have never seen any require classified wiring methods.

If they did would not the genset also have to have a classified rating to use in a classified area?

I was looking at the 150 PSIg of gas pressure inside of the building with the possibillity of flanged valves, pressure gauges,reliefs, etc. where there is a potential for leaks.

 

[weressl]

What do you believe could trigger the need?

We install many indoor gas fired gensets and I have never seen any require classified wiring methods.

If they did would not the genset also have to have a classified rating to use in a classified area?

As I described earlier, that is why the ventillation adequacy needs to be addressed, so it can be an unclassified area. it would be rather difficult to build a Div. 2 genset, not to mention Div 1.

It would be beneficial if NFPA497/NEC Art. 500 recognize a formal Nonhazardous Classification, maybe Division 0 to indicate that although flammables are present in the area, but by the (mechanical) installation provision it is assured that they can never form an ignitable mixture. This would assure that the issue was addressed, investigated, formally declared and documented to be non-hazardous.

 

[weressl]

I was looking at the 150 PSIg of gas pressure inside of the building with the possibillity of flanged valves, pressure gauges,reliefs, etc. where there is a potential for leaks.

As I noted before the 150PSI supply at the user site is not likely. Even if it is a large customer the pressure is reduced before it enters the customers' lines.


Here is a paste from a CAT

215 ekW @ 1800 rpm : G3406

Fuel pressure kPa/ PSI 10.3 - 34.5/ 1.5 - 5

 

[Fulthrotl]

Interesting. Gas supply at the user point is usually more like 0.5PSI for household
service and maybe in the 15-20PSI range in large commercial or industrial user's site.

the only time i've seen service pressure above 100 PSIG is at a steam plant.
it's a 60" incoming line... but it's running i believe seven units,
generating 1,600 MW.

150 seems a bit high.

 

[iwire]

As I described earlier, that is why the ventillation adequacy needs to be addressed, so it can be an unclassified area.

I generally do not see any ventilation at all until the genset is running.

But 150 psig is something we would never see.

 

[dicklaxt]

This link may solve or give the author of the OP a path to follow or hang his hat on.

http://www.eng-tips.com/viewthread.cfm?qid=61335


dick