Where is the NH3

[islandengineer]

Hi everybody, First day as a member but I have used your advice quite allot in the past, Anyhow, I am a shift Engineer at a seafood processing facility, We have 12,500 lbs of Nh3 in the pipes joined by 1 common HPR, 3 LPR’s, 2 Intercoolers, 3 screws , 1 compound, 5 recips and 4 rotary boosters,
We do IQF, Plate Freezing, Cold Storage and Ice Making.
My question to you is: Lately we have been continuously adding Nh3 to the system as our HPR is constantly running dry, We have tested for leaks everywhere we can including Evaps, Condensers, Condenser Water, Liquid Pumps etc. we do multiple defrosts everyday but still cannot understand where all that NH3 is hiding or Leaking from. I have a feeling that this thread may take some time so I will just start here, Thank you in advance for any ideas.

[NH3LVR]

Welcome Islandengineer!

Have you checked the Relief Valves? Have been through this several times and have a couple of tricks.
If you feel this is a possibility, describe how your relief system is plumbed and we will try to help.
Always good to see another NH3 guy sign on.

[islandengineer]

not sure if I am doing this correctly so you may see this twice till I figure it out...

It has been my experience that if a safety valve is leaking that I have heard a telltale burping sound, however this may not be the case,
All the pressure vessels have redundant safety’s (2) the economizers have (1) , these collect depending on there location and make up 3 separate stacks protruding from the roof of the plant. All the recips and boosters are relieved back into the suction side if the compressor via external piping or as in the case of our 2 York recips which are relieved internally back into suction.

[NH3LVR]

All the pressure vessels have redundant safety’s (2) the economizers have (1) , these collect depending on there location and make up 3 separate stacks protruding from the roof of the plant. All the recips and boosters are relieved back into the suction side if the compressor via external piping or as in the case of our 2 York recips which are relieved internally back into suction.

You did it correctly, no worries. Even if you do not we will coach you until you get it right.
Lets go over the possibilities one at a time.

The Screws often have the cheap aluminum reliefs installed. If this is the case, these are guaranteed to leak after a short time.
The Pressure Vessels have two reliefs each, mounted on a two position valve, is that correct? You can turn these to isolate one valve at a time. Which is handy if only one valve is leaking.
The most common offenders are the HP Receiver and the Screws.
If you can open the lines in the Engine Room you can test with a Sulfur Stick. NH3 will remain in the piping for a long time. ANY smoke indicates a leak.

One test is to take a Sulfur Stick to the Roof and check the outlets.
Another is to put a Balloon or Condom over the End of the Stacks (No Snickering allowed), securing it with a rubber band. This does not always work as the Relief Valve Piping is sometimes quite leaky. It is generally not pressure tested.
Remember that the leakage is not continuous, it may come and go.
We now install a air fitting in the piping to purge the lines. If you have a NH3 Detector in the line it can be very helpful.
One of our Customers was plagued with seeping valves. We installed Rupture Discs http://www.hantech.com/documents/PDF/K209.pdf under all the valve and solved the problem 100%.
It is not a cheap solution however, and requires a little repiping of the Vent Line.
I alway begin by checking the outlets and then break the joints in the Engine Room.

Another possibility is a leak in the Condenser. This is usually obvious by smell and the water turning black.

Let us know how you are making out.

[The Viking]

Another is to put a Balloon or Condom over the End of the Stacks (No Snickering allowed), securing it with a rubber band.

I remember having to explain a half empty pack of condoms in my tool box to the missus, I still don't think I managed to convince her

[NH3LVR]

.Another possibility is a leak in the Condenser. This is usually obvious by smell and the water turning black.

I am required to correct myself on this statement.

I have seen the water turn black under one circumstance. This was with Aluminum and Galvanizing both present. This probably will not be the case in your Condenser.

[islandengineer]

I understand exactly what you are saying, however we did a major refit approx 1.5 years ago and at that time we replaced all the safety valves on all the receivers as per inspectors insistence, now having said that a couple of months ago I started the plant up after being shut down for an extended period of time, as it turns out, on one of the LPR’s an isolation valve was closed and not tagged as being so, when I started the plant the pressure inside that LPR reached a critical level 150+ psi and “burped” a safety, How that happened remains a mystery , I subsequently open the isolation valve and the pressure returned to normal,
SO what I am going to do is climb the Relief stack and put a rubber on as you suggested (I am sure I have one or two floating around my truck) and let that go for a while to observe. It makes sense that the popped valve did not seat correctly and is weeping out my NH3. Considering the low side, do you think that it would leak more under operational conditions as apposed to a static state?

To The Viking, just keep one those condoms partially inflated with some NH3 gas and then let the missus inspect it, She will never doubt you again

[NH3LVR]

Considering the low side, do you think that it would leak more under operational conditions as apposed to a static state?

If by static you mean higher pressure I would imagine so.
I have seen leakage at 2-3 Lbs on the low side. If it were not for the Monitor we probably would not have known it was seeping.
Leave it on awhile-and prepare to explain yourself when the Plant Manager invites you to his office!

[US Iceman]

To The Viking, just keep one those condoms partially inflated with some NH3 gas and then let the missus inspect it, She will never doubt you again

Or, she will think there is something seriously wrong with your health.

Lately we have been continuously adding Nh3 to the system as our HPR is constantly running dry,

If there is that much ammonia leaking out and the smell is not obvious, then you have to ask yourself what could be masking the smell?

My first impression is probably the condensers leaking. The water flowing over the coils will absorb ammonia like crazy. As soon as the water is shut off, everyone notices a new smell that was not there before when the water was running.

If has to go somewhere, and there should be an odor. If there is no odor, then something is absorbing the ammonia.

By the way, does your system have a water dispersion tank at the end of the relief valve vent headers?

Always nice to see another ammonia guy on here. Welcome to the RE forums.

[islandengineer]

I originally thought that may be a leak in one of the condensers but I dipped test paper in the water of all 4 condensers and it came back clear, I realize the affinity of NH3 to H2O so the condensers were my first thought. Last June we had a stand-alone condenser leak, we engineers barely noticed a smell but the line workers here whined and moaned like it was the end of the world so I believe the smell would be noticed.

There are no water dispersion tanks in this system,

What about Oil entrapment? We recycle oil out of receivers, I collect the oil in 45 gallon barrel then I heat it, filter it and reuse it in our Old 4 Fuller rotary boosters, these boosters are lubricated by Manzell Force Feed Lubricators that are as old as dirt so trying to keep them at there specified drip rate is next to impossible so they tend to over lubricate and send the oil to the intercooler where it is drained almost daily. Any idea how much NH3 will dissolve into oil? I know it is a bit farfetched. We seem to be adding 100 to 300lbs of NH3 every 2 or 3 weeks.

[US Iceman]

What type of purgers do you have? Are they manual or automatic?

I doubt you are lossing that much ammonia just from oil draining.

Does the level continue to decrease slowly and sometimes suddenly increasein th ereceiver?

If not the condensers, then it might the relief valves weeping or possibly old/bad with wet insulation.

[islandengineer]

The purger is automatic and works well. The oil level (especialy in 1 intercooler) in the recievers increases gradually because of the amount we need to feed the boosters, I really doubt that the oil is the culprit in this case but I just thought I would throw it out there.
I am going to heavily scrutinize the one safety valve I believe to have popped a few months ago and also scrutinze all 4 condensers.

[Jryffel]

Suggest you put a camera on your HP Receiver and your condensers. This is the two most common places for theives to steal your ammonia. Believe it or not we have an epedemic of this kind of stealing. It seems that one of the main ingrediants or at least the process is ammonia when manufacturing Crack Cocaine. We have had the same kind of complaints from several customers and after research trouble shooting the system we found out about the stealing.

[Paulajayne]

Hi

Theft is a possibility.

"Anhydrous ammonia is a key ingredient in the illegal production of methamphetamines (meth).

Anhydrous ammonia can be used illicitly for the production of the highly addictive drug methamphetamine (meth), a powerful central nervous system stimulant. One method to produce meth requires ammonia which is stolen from agricultural chemical dealerships and farms.

Criminals cause anhydrous ammonia incidents when nurse tank valves are left open; ammonia is transferred into makeshift containers; or hoses and/or fittings were loosely attached to valves of nurse tanks causing leaks and spills."


A security camera pointed at the tower may reveal all.

Paula

[brian_chapin]

I am going to heavily scrutinize the one safety valve I believe to have popped a few months ago and also scrutinze all 4 condensers.

I know that Hansen recommends replacing any PSV that has activated and can't imagine that the other manufacturer's wouldn't recommend the same thing.

I suggest rupture disks with the little gauges on them in line before the PSV. You'll always know if a PSV has popped there and I've never come across a rupture disk weeping like PSVs are known to do from time to time.

[islandengineer]

I do not believe that theft is an issue here as we have a cage containing at least 7/8 100lb bottles of NH3 that would be much easier to steal.

[Jryffel]

How much ammonia do you have to take on per month?

[US Iceman]

I am going to heavily scrutinize the one safety valve I believe to have popped a few months ago and also scrutinze all 4 condensers.

Let me ask this... Did the continual replacement of ammonia start after or before the relief valve problem?

If a valve popped, it may not have reseated tightly.

[TXiceman]

Relief valves are notorious for not reseating when they have lifted. You need to just replace any valve that has lifter.

Ken

[islandengineer]

We are in the fishing industry and so we are a seasonal operation, the safety valve popped at initial start up of the season, before that the system was pumped down into the HPR (plus one auxiliary HPR used for storage) so in answer to your question it was definitely after the valve popped, I have now bagged the relief discharge pipe to see if it is going to inflate, I will also check it later for any sign of NH3 with a test paper. I have also realized that we have one unused evap in our icebin, It may be that the liquid line has been weeping into that evap so that is the next thing I will check, I am going to defrost it and check the HPR level before and after.

[islandengineer]

Hi everybody, It seems as though the NH3 is not leaking (or at least I have not found any evidence of a leak) I have found various liquid line valves that are leaking continuously as well as poor operation of the equipment i.e.; lack of defrosts, doubling up on freeze cycles etc. have caused the NH3 to drift around the plant hiding in the pipes and ice machines, the low side seems to be unusually full as well. So through valve adjustments/replacements and a education in proper operation to the operators I have managed to "find" most of the NH3.
Thanks for all you help, I will keep visiting this site and offer my knowledge to anyone who needs it.

ps. I switched to the alternate Relief Valve on the LPR and will be replacing the suspect Valve.