Anhydrous Ammonia

[chester7477]

We are wiring some 12vdc emergency shut off solenoids on a 25,000 gal anhydrous ammonia bullet tank pump that is used to fill 1000 gal portable tanks for farm applications. I noticed that the solenoids are not listed for hazardous locations. Does this application require hazardous locations wiring methods?

Also, The anhydrous bullet tank sits 16' away from a 18,000 gal propane bullet tank that they use to fill their propane delivery truck. From what I read in the code book about bulk storage tanks is that we should be out of the propane classified area because it is over 10 feet away. Is this correct?

 

[rbalex]

Has the electrical area classification been documented as required by Section 500.4(A)?

 

[chester7477]

No it has not... most of these sites are not documented.

 

[IntrinsicSafety]

It may be a Div 2 area, possibly even Div 1 in some places.

Best get the area classified as rbalex suggested.

 

[rbalex]

No it has not... most of these sites are not documented.

That's a Code violation in itself. [Section 500.4(A)]

 

[chester7477]

Is hazardous location wiring required around Anhydrous Ammonia? ...Or is it just a corrosive issue?

 

[augie47]

Class 1 Group D, I believe

 

[kwired]

Is hazardous location wiring required around Anhydrous Ammonia? ...Or is it just a corrosive issue?

Been quite a while since I did work around anhydrous ammonia, but from my recollection it does not create an art 500 classified location.

Good thing it doesn't either, because it will attack the galvanizing on GRC, uncoated black pipe will actually last longer around this stuff but is not any listed raceways that are made of black pipe.

It doesn't do so well with copper either, you ever have service calls on this be prepared to replace switches, contactors, etc. as they will have corrosion on them and the connections to your conductors. My suggestion is keep motor starters as far away as practical and have only basic control switches near where this product will be present. Don't matter how sealed an enclosure is - it finds a way inside.

 

[rbalex]

For those that insist on guessing, I suggest reviewing the last IN in Section 500.5, primary text. Anhydrous Ammonia has its own set of rules per ANSI/CGA G2.1. I also suggest reviewing NFPA 497, part 4.2.5 which suggests anhydrous ammonia can indeed create a hazardous location.

Electrical Area Classification is becoming a design DIY subject on this website.

Get someone qualified to properly document the electrical area classification THEN decide on the proper equipment and wiring methods.

 

[kwired]

Most of what I am finding about it says it is flammable, but not explosive.

I am reading it can react with certain things and create some explosive gases, or if it should get broken down and release the hydrogen that is part of what makes it up - that is definitely hazardous location gas.

 

[rbalex]

Most of what I am finding about it says it is flammable, but not explosive.
...

Yes; so? You should review NFPA 497[2017}, Part 3.3.6 and Table 4.4.2 including footnotes d and f.

 

[paulengr]

Anhydrous ammonia is definitely explosive. Search the internet for articles about West, Texas where a fertilizer plant basically took out a town. But that being said it is used extensively as a refrigerant in food plants, cold storage, ice plants. And it is very easy to kill...just spray it with water to knock it down.

It is very flammable and corrosive. But the flammability limits are very narrow. So much so that if you have a tank leak and it dumps out onto the ground, hopefully contained by a berm, the vapor pressure is such that it CANNOT reach the flammability limits so never becomes explosive in open air. If you contain or pressurize it though such as an indoor tank, look out! Hence almost no safeguards aside from asphyxiation and dumping water on it are used.

Either way, don’t guess. The fertilizer industry has some really good guide books on handling ammonia as do the ammonia compressor companies. Mostly around storage you end up wiring for division 2 but it’s not really required, more of a paranoia thing.

 

[kwired]

Anhydrous ammonia is definitely explosive. Search the internet for articles about West, Texas where a fertilizer plant basically took out a town. But that being said it is used extensively as a refrigerant in food plants, cold storage, ice plants. And it is very easy to kill...just spray it with water to knock it down.

It is very flammable and corrosive. But the flammability limits are very narrow. So much so that if you have a tank leak and it dumps out onto the ground, hopefully contained by a berm, the vapor pressure is such that it CANNOT reach the flammability limits so never becomes explosive in open air. If you contain or pressurize it though such as an indoor tank, look out! Hence almost no safeguards aside from asphyxiation and dumping water on it are used.

Either way, don’t guess. The fertilizer industry has some really good guide books on handling ammonia as do the ammonia compressor companies. Mostly around storage you end up wiring for division 2 but it’s not really required, more of a paranoia thing.

Where I have run into it is used for fertilizer. Stored and transferred in tanks, but if there were to be a leak, will be in open air. I can see where there could be more hazard if the application were indoors. These outdoor fertilizer applications I think there is more direct hazard to user exposure than there is fire or explosion risk.

Never seen any pumps for this wired with Art 500 wiring methods. Never seen any wiring near the tank/pump besides wiring for the pump and maybe some lighting if there is intent to make any transfers at night. Too corrosive and they generally keep everything else away from it.

It don't play well with galvanized metals - which is basically what art 500 calls for when it comes to wiring methods They store it in non galvanized tanks and use non galvanized piping. They may paint the tank and piping white to reflect sunlight to keep it cooler and cut down on surface rust.

 

[hillbilly1]

Anhydrous ammonia is definitely explosive. Search the internet for articles about West, Texas where a fertilizer plant basically took out a town. But that being said it is used extensively as a refrigerant in food plants, cold storage, ice plants. And it is very easy to kill...just spray it with water to knock it down.

It is very flammable and corrosive. But the flammability limits are very narrow. So much so that if you have a tank leak and it dumps out onto the ground, hopefully contained by a berm, the vapor pressure is such that it CANNOT reach the flammability limits so never becomes explosive in open air. If you contain or pressurize it though such as an indoor tank, look out! Hence almost no safeguards aside from asphyxiation and dumping water on it are used.

Either way, don’t guess. The fertilizer industry has some really good guide books on handling ammonia as do the ammonia compressor companies. Mostly around storage you end up wiring for division 2 but it’s not really required, more of a paranoia thing.

I wired an ice plant several years ago, they had an emergency dump into a water tank if a leak developed. Some real nasty stuff. The maintenance guy said his brother lost a hand when someone broke off a guage. He grabbed the shutoff valve and quickly shut it off, but not before freezing his hand.

 

[kwired]

What i read about the plant in West Texas seems like there already was a fire for reasons not confirmed. Said fire raised temp and pressure in a tank with anhydrous in it, the explosion was result of tank failure and the sudden pressure release and not so much direct ignition of anhydrous.

I had a propane tank that was potentially overfilled that did about same thing but on much smaller scale once, hot summer day tank ruptured. Lucky it never was ignited by anything in that case but the pressure release blast still did some damage in the shed it was stored in.

 

[don_resqcapt19]

Anhydrous ammonia is definitely explosive. Search the internet for articles about West, Texas where a fertilizer plant basically took out a town. ....

That was not an anhydrous ammonia explosion...that was ammonium nitrate. A solid product and the same product that killed almost 600 people in a Texas City ship explosion in 1947.

 

[don_resqcapt19]

Been quite a while since I did work around anhydrous ammonia, but from my recollection it does not create an art 500 classified location. ...

This language added to 500.5(A) for the 2017 code, seems to imply otherwise.
(quote] Refrigerant machinery rooms that contain ammonia refrigeration systems and are equipped with adequate mechanical ventilation that operates continuously or is initiated by a detection system at a concentration not exceeding 150 ppm shall be permitted to be classified as “unclassified” locations.[/quote]
One of the issues with this product is that the DOT transportation placard for anhydrous is green, non-flammable gas. The DOT has classified it as a non-flammable gas because their standards say a flammable gas has an explosive range that does not exceed 13%. Anhydrous has a LEL of 15%. As a result many do not understand that this product can be explosive.

 

[kwired]

This language added to 500.5(A) for the 2017 code, seems to imply otherwise.
(quote] Refrigerant machinery rooms that contain ammonia refrigeration systems and are equipped with adequate mechanical ventilation that operates continuously or is initiated by a detection system at a concentration not exceeding 150 ppm shall be permitted to be classified as “unclassified” locations.

One of the issues with this product is that the DOT transportation placard for anhydrous is green, non-flammable gas. The DOT has classified it as a non-flammable gas because their standards say a flammable gas has an explosive range that does not exceed 13%. Anhydrous has a LEL of 15%. As a result many do not understand that this product can be explosive.
[/QUOTE]
So there can be classified location in refrigeration equipment rooms. Doesn't say anything about other applications, in particular outdoor storage and transfer stations for fertilizer uses, which happens to be what I am more likely to run into. I have never run into such situation where hazardous location wiring methods were used.

 

[don_resqcapt19]

So there can be classified location in refrigeration equipment rooms. Doesn't say anything about other applications, in particular outdoor storage and transfer stations for fertilizer uses, which happens to be what I am more likely to run into. I have never run into such situation where hazardous location wiring methods were used.

Given the high LEL it may be unlikely that you would have a flammable mixture in an outside installation.

 

[rbalex]

I have said before that the Class definitions are in terms of “possibility” NOT “probability”:

500.5(B)(1) Class I, Division 1.

A Class I, Division 1 location is a location:

500.5(B)(1)(1) In which ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors can exist under normal operating conditions, or

500.5(B)(1)(2) In which ignitible concentrations of such flammable gases, flammable liquid–produced vapors, or combustible liquids above their flash points may exist frequently because of repair or maintenance operations or because of leakage, or

500.5(B)(1)(3) In which breakdown or faulty operation of equipment or processes might release ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors and might also cause simultaneous failure of electrical equipment in such a way as to directly cause the electrical equipment to become a source of ignition.
…

500.5(B)(2) Class I, Division 2.

A Class I, Division 2 location is a location:

500.5(B)(2)(1) In which volatile flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors are handled, processed, or used, but in which the liquids, vapors, or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or systems or in case of abnormal operation of equipment, or

500.5(B)(2)(2) In which ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors are normally prevented by positive mechanical ventilation and which might become hazardous through failure or abnormal operation of the ventilating equipment, or

500.5(B)(2)(3) That is adjacent to a Class I, Division 1 location, and to which ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors above their flash points might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided.

It does not matter how unlikely a classified location is, it only has to be possible under the right conditions. The envelope around a pressure relief vent is typically Division 1, but in fact, it may never “pop”.

The point is while anhydrous ammonia is indeed an atypical flammable material, under the right conditions it can create a classified location. On top of its flammable properties, it is also toxic and can be subject to Section 100.12(B) as well. This is why it has its own special rules, It should also be noted FedOSHA and/or State OSHAs can enforce any applicable ANSI Standard.

One of my biggest arguments was to get the term nonhazardous removed and replace it with unclassified as appliable to emphasize that someone qualified to make the judgment had reviewed the conditions of installation and documented it.