View Full Version : A square peg in a round hole!

24-07-2011, 11:37 AM
Working away recently on a Ammonia spiral freezer plant.
Which had a leak from the base of a Hanson Liquid strainer. Which to access required the removal of the system charge.
When the strainer was stripped, a tapered 1/2" plug was found to be in the parallel tapped hole. Which was intended to have a valve in it for safe purging of the strainer.

This plug had been in place for quite a few years before it failed. But once it did tightening up failed to resolve the leak.
Having removed the charge which was estimated at anywhere between 2-4ton.
Actual was nearer 2 ton bearing in mind that the leak had been blowing for 3-4 months prior to charge removal.
I suspect that the actual recharge will be around 3 ton once completed.

Anyway I started to look elsewhere and discovered the below - 1/4" flare fitting.
Which was on the top of the evaporative condenser discharge inlet pipe.
Intended for use as a purge point I suspect?

Given that this was not accessible and had never been used (No access normally).
The resultant copper sulphate deposits show what even the slightest ammonia contamination will do to brass / bronze.
I cannot say where the contamination came from as the valve it was attached to passed a Pressurised leak test and a nose test with part of the charge in.

The Ammonia had weakened the fitting to the extent that when trying to unscrew the fitting it snapped of within the valve.

It just shows that ammonia need steel fittings irrespective of perceived usage.



monkey spanners
24-07-2011, 03:23 PM
We've had problems with plastic boxes just falling to bits in dairies and have been told its due to the ammonia from what the cows left behind!

Jon :)

24-07-2011, 04:52 PM
Yep Jon.
Ammonia seems to eat the plasticisers in the plastic making the plastic brittle.
Ask anyone who uses Vacuum pumps that vent through the plastic handle.

24-07-2011, 07:05 PM
i do some work at local maggot producers and copper anywhere dissapears quicker than you can blink.

29-07-2011, 05:59 AM
Hi Grizzly.
had a similar problem with a plant over a weekend, plant probably 5 years old, installed by others. Call was that plant was full of ammonia vapour, I was the last resort. [ the only one that answered the phone on a sunday ].
Turned out that the coil manufacturers pressure test points were still fitted to coil headers [ 1/4 " brass schraders ]. pretty blueish lumps of what was brass

29-07-2011, 11:52 PM
Hi Grizzly.
had a similar problem with a plant over a weekend, plant probably 5 years old, installed by others. Call was that plant was full of ammonia vapour, I was the last resort. [ the only one that answered the phone on a Sunday ].
Turned out that the coil manufacturers pressure test points were still fitted to coil headers [ 1/4 " brass schraders ]. pretty blueish lumps of what was brass

So how did you deal with the vapour?
Water curtain?
Extract fan?
Don suit and respirator / B.A. and locally isolate (been there and the site manager who was my "Buddy" crapped himself).
Hold your breathe and dribble water over the joint?
Lots of options to choose, none of them recognized by the "You can't do that brigade" but highly efficient all the same!
Made the mistake of holding a long rolled up ammonia hose betwen my legs whilst I attempted to cable tie the looped hose.
No smell but enough vapour left to make my eyes water, only it wasn't my eyes the ammonia was burning.

30-07-2011, 02:13 AM
Hi Grizzly.
Fortunantly all headers were accessable from ceiling space above tunnel freezer, used BA set with buddy tagging along with BA set. Isolated everything and did a pumpout. Lots of temporary extract fans and opened everydoor in plant. The problem was finding enough steel BSP plugs to replace the eight schraders [ on a sunday night ].
On the monday the office ladies did complain about itchy problems.
Same plant a couple of years later during production, the pilot on the main PM liquid solenoid let go and sprayed liquid NH3 everywhere, the o/ring let go for no reason, replaced with later version. Actually had one in vehicle. Similar result with Fire Service added to problems, all staff in evacuation areas, red flashing lights everywhere the whole nine yards.

30-07-2011, 09:26 AM
Well done my friend, a cool head an common sense can deal with most problems.
Provided you have the requisite knowledge in the first place.
At least you had access to a buddy.
Most of my humorous stories involve the response to ammonia leaks by others, the fire brigade and their chemical response units do feature in quite a few!

Just to add to everyone reading this.
Serious incidents with ammonia are few and far between.
And yes the lengths you have to go to when faced with even a small sustained leak can seem extreme.
Which in itself scares a lot of people. But the areas involved are almost allways totally clear of anyone. So good at giving an early warning is ammonia unlike most other dangerous substances.
Including *****s.
So as an engineer who is in the most danger?
Those that treat the plant with the respect it deserves or those that can become complacent?

01-08-2011, 04:48 AM
Hi Grizzly.
It has always been a bone of contention with me personally that our trade is not a " registered trade "as per electricians, plumbers, drain layers, gas fitters. the old health risk to society thing.
Never mind, the enviroment is more important to the greenies, we mere humans are replacable and expendable.

01-08-2011, 07:22 AM
I wish more guys had a chance to work with Ammonia.
Then there would be less people running around making unqualified and unfair statements.
I don't normally think fast enough to have the quick clever reply sadly!
However having just been introduced to the general manager of a regional cold store who I would be running it's engineering department for (Dept. read just me!)
Whilst standing in the middle of an open plan office full of mainly female staff. He Proudly announces that "As the General Manager if the Ammonia plant where to go wrong. He was the one that would end up in court!"
I replied - "If it goes wrong for me, I am the one that could end up dead!"

Says it all really!

Hey! How green is working with Ammonia and Nuclear?
Keep chilling!

03-08-2011, 07:14 AM
Hi Magoo
Got to agree with you about being registered. We have Arctick here but it's only a refrigerant handling license. Sometimes I think it's only a revenue raiser, a domestic fridgie has the same license as an industrial fridgie, most domestic / commercial guys run a mile when it comes to ammonia.
Grizzly, I have seen water ball valves (plated brass valves, look like S/S) on receivers as purge valves, got them changed very quickly. Have also seen other brass fittings used, when I advised the client he said they have been there for years with no trouble, just lucky I reckon.

04-08-2011, 03:14 AM
Hi PaulZ.
I agree, the arctick thingo is about to start here I have on good information. Another tax grab.

05-08-2011, 03:17 AM
Hi PaulZ again.
here the system dictates ammonia service engineers/ mechanics require a "hazardous substance handling"certificate. $500.00 plus later, and I was instructing the instructor on safe practices.
Any ideas on were to start with getting the ammonia trade registered, the AS/NZS Standards people work together between OZ and NZ. This could be a start. Your thoughts. Hell I might start harassing my local MP., and bombard his office with emails.

05-08-2011, 06:34 AM
Hi Magoo
Nothing like that here yet, $500 is a bit steep, our Arctick license is $100 or there about and that's for 2 years.
I think our only chance would be through Arctick, but because the ammonia field is so small I don't see much changing as they wouldn't make enough money from the ammonia guys. We could lobby the Arctick guys and see what they say.

06-08-2011, 01:41 AM
Hey Magoo don't forget about the fillers cert.
So there's the safe handling (hazardous substance handling) and that lets us handle NH3 and then the ridiculous filling cert the same course that the service station attendants have to fill your BBQ cylinder so we can decant NH3 into cylinders. A joke. I was hoping after "Tamahere" there would be some drastic changes to our industry (ie: registration) but all I have seen is a few ammendments to the regs and the above box tickers.

There is a review underway of Compertenz and the current apprentiship system which I have some involvement in and I'll be pushing regulations, standards and registraion. It might be a good place to start.

06-08-2011, 03:57 AM
Hi Superfridge.
We seem to be making progress, as for Compertenz, that is a joke. Maybe I could be envolved somewhere in the system that will fire the whole system up.
Had in the past a situation where a young chap just out of his time was appointed an accessor. he was hardly old enough to shave let alone know anything about the trade. As for the module and accessment type approvals, the blind are leading the blind.
Grumpy magoo