Ammonia clearances
- Thread starter 347sparky
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- Mission Viejo, CA
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- Professional Electrical Engineer
I doubt ammonia is being used as a motor fuel in the scope of Article 514. A better general reference is the last paragraph and IN for Section 500.5(A) or 500.6(A)(4) IN 2. If those don't apply either, then electrical area classification for ammonia locations should be determined by NFPA 497.
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kwired
Electron manager
- Location
- NE Nebraska
Anhydrous ammonia is not an art 500 hazardous material AFAIK.
One thing I do know about anhydrous ammonia is you do not want to use typical galvanized hazardous location wiring methods, the zinc in the galvanized finish is not going to last long in anhydrous ammonia environment. Anhydrous tanks and piping are black iron for this very reason. Corrosion protection is paint, no galvanizing. Bare rusty metal lasts longer in that environment than galvanized does.
What little anhydrous I have been around has always been non metallic raceways and enclosures. I don't know about stainless, but it may be acceptable.
Anhydrous doesn't get along well with copper either,or maybe it gets along too well depends how you are looking at it I guess, so you will have problems with components inside the raceways and enclosures as well. I would think best thing would be a pressurized system with supply coming from a location that is ammonia free, because no matter how well you think you have things sealed, it finds a way inside.
One thing I do know about anhydrous ammonia is you do not want to use typical galvanized hazardous location wiring methods, the zinc in the galvanized finish is not going to last long in anhydrous ammonia environment. Anhydrous tanks and piping are black iron for this very reason. Corrosion protection is paint, no galvanizing. Bare rusty metal lasts longer in that environment than galvanized does.
What little anhydrous I have been around has always been non metallic raceways and enclosures. I don't know about stainless, but it may be acceptable.
Anhydrous doesn't get along well with copper either,or maybe it gets along too well depends how you are looking at it I guess, so you will have problems with components inside the raceways and enclosures as well. I would think best thing would be a pressurized system with supply coming from a location that is ammonia free, because no matter how well you think you have things sealed, it finds a way inside.
- Location
- Illinois
- Occupation
- retired electrician
It becomes a flammable vapor when it leaks out if its containment so why would it not be covered by Article 500 and 501?
kwired
Electron manager
- Location
- NE Nebraska
OK, I'll buy that, but only in some circumstances.
The only time I have been around it is for use as Agricultural fertilizer product, and it is handles outdoors in the open. Not much threat of being flammable in that circumstance. Indoors in confined areas, I may agree it could become flammable or even explosive.
I base this on several different places where I read basically the same thing that went something like this:
The other hazards of the material far outweigh any fire hazard when out in open spaces. (I think)
I know in an event where it has leaked you do not want to be anywhere near that stuff without protection, the best protection is a constant showering of water along with additional protective clothing and a self contained breathing apparatus. Emergency responders would really much rather have the stuff burning I would think - then it would at least be more obvious where it is at.
Correct, not used as a motor fuel but is being filled in portable 1000 gallon tanks. I would like to find if there is any specific requirements like the table shows such as 20' radius around the tank or "x" amount of feet around a fill valve is a classified area.
Section 500.5(A) mentions adequate ventilation may be a unclassified location, and this filling station is in the wide open outside.
500.6(A)(4) IN 2- Looks like I need to find ANSI/CGA G2.1-1989.
kwired
Electron manager
- Location
- NE Nebraska
Like Bob said, you probably need to look into NFPA 497 (which I am not familiar with) to determine if you have a classified location.
I can tell you from experience that anything in at least 100 foot will be subjected to pretty severe corrosion, and anything within about 100 yards will likely have some corrosion at some point. The stuff is just plain nasty. It seeks water, it is like a predator and water is about the only prey it is really interested in. If copper or zinc and some other metals come along it will entertain itself with those, but it really wants water. Inside your enclosures is where condensation occurs - therefore there is water in there for it to seek out. If you are indoors - it may be a different ballgame altogether.
Thanks for the info. Sound like I should worry more about the corrosiveness than the explosiveness. Since it is sprayed on fields out in the open I could not imagine it being explosive as gasoline. I thought maybe there is a classified area within so many feet of dispensing.
The area I was at had a large tub full of water for an emergency. If you had any skin contact with the anhydrous ammonia you need to jump in the water and stay for 15 minutes. I joke with the guys they need a hot tub out there because when they fill tanks in the fall the temps can be anywhere from 30-70* F.
kwired
Electron manager
- Location
- NE Nebraska
30F is warm compared to what that anhydrous ammonia will feel like on your skin.
Anhydrous Ammonioa is nothing to play around with for sure. Some deadly stuff.
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9757
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9757
Thanks for the document. This is the only blurb about electric installations:
"Electrical equipment and wiring for use in ammonia installations shall be general purpose or weather resistant as appropriate."
This would be my concern also. I had a customer complaint about a contactor that was eating up contacts. I had him check his control circuit which was 2-wire. It ended up that there was a pressure switch on an ammonia line with an ammonia leak at the switch. The ammonia attacked the switch, the switch caused the contactor to chatter.
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