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Grizzly
23-02-2014, 09:57 AM
Within the end of the adjustable spanner I was using to be precise!

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Oh! And the system which had approx 400kgs of Ammonia in it could not be isolated at the time.

That's another story which has a happy ending, where 3 days later myself and my good friend and colleague.
Had safely controlled the unavoidable release of 400kg of ammonia.
Repaired the leak and rectified future isolation issues,recharged the system and set it to work.

Despite several headless chickens wanting to cordon off a busy town area and involve the fire brigade etc.
Suffice to say If some had been allowed panic anymore than they were!
Then Grizzly would of been on telly!


Can you guess what this is? It's upside down by the way.


11236

Grizzly

hookster
23-02-2014, 10:37 AM
I wonder when that particular plant had its last survey judging by the condition.
I would be interested if this was lagged or just exposed to the elements?

I was recently on a site where the oil receiver was very badly corroded and was informed that it "Was an Old plant" this is not really an excuse or justification for the condition.
There are "miracles" that we can all use to prevent catastrophic failures from regular thorough inspections, primers, paints, rust converters etc etc.

The old adage is still PREVENTION IS BETTER THAN CURE

josef
23-02-2014, 11:37 AM
Grizzly, watch you on TV, no problem, just a better opportunity.
Yes servicing, inspection, poor insulation, great enemy, the investor does not accept the warnings of engineers, thinks only of his money, prevention, prevention of + struggle with the customer.

Josef.

Grizzly
23-02-2014, 12:02 PM
Hi Hookster.
You are both jumping to conclusions (albeit reasonable ones!) and assuming with hindsight!
This plant has been well maintained over its long life and when this happened was within 1/2 months of decommissioning.
The reason for the corroded state of this and the other 28 valves is because they regulate the injection of hot gas into a ice plate. As part of the defrost (Ice Harvest) on a 80ton Ice plant.
Therefore there valves operate with a range of say -20c to +25/30c on a 9 minute cycle with a 1 minute Harvest cycle.
So it is reasonable to expect corrosion internally and externally. What no-one including myself expected was the amount of internal corrosion.

Below is a comparison of the original wall thickness (poor focus I am afraid!)


11237

Also a picture of the resultant leak 24 hrs after the valve failure. Yes that is white Ammonia vapour!
This picture was taken wearing just a respirator and standing to the side of the vapour cloud.
No danger no stress because a drager is screaming above 30 ppm.
Which is my point really everyone is so paranoid about Ammonia and there ill informed perceptions that anyone that dares to enter a room with it in.
Sadly the very powerful but ill advised few are making what is reasonable and safe action and practises.
Non acceptable because they do not realise that is trained correctly in the first place Sh*t can be dealt with safely.
I know you have done similar and Hey! We are still here! Are we Not?


My whole premise of this post is to few mention that they have dealt with these REAL ISSUES!
Whereas there is a whole industry being built of people in offices dictating without just cause or experience.
Maybe its time for me to retire?
The customer that keep asking me back may disagree?
But it's hard work sometimes is it not?
Grizzly




11238

Grizzly
23-02-2014, 12:36 PM
Thanks Josef.
The whole incident happened because, the plant engineer had a leak on one of the flexible hoses seen in the 2nd photo.
So at 05.30hrs on a Wednesday morning, he calls me asking me to attend on a emergency breakdown.
Whilst en-route the 150miles. I phone the engineer and ask more about the problem.
Resulting in my asking him to isolate the main Liquid line valve from the ammonia pump for that set of plates.
So that when i arrive some of the liquid within the plates will of boiled off.


On arrival I am told that as the engineer cannot find his spanner he was unable to remove the relevant valve cap.
I to try and fail with my trusty Bahco, Leaking hose identified. I attempt to locally isolate the hose.
Hot gas line to distribution manifold shut, when I go to remove the hose line valve cap.
The above happens!!
At this point I told the engineer who was in the corner next to the emergency exit ladder. To get out of the plant room via the main door with me following.
I then enter wearing my respirator to yet again try and shut the main surge drum / ammonia pump liquid line
Isolation valve. Yet again I failed The guy is huge mind, so I put it down to me being weak!
We later found his spanner (A 3ft adjustable) No-wonder the cap could not be undone.

At this point my colleague rang having been informed that I had been called out to an ammonia leak, offering his assistance.
Customer agreed, he attends and within 24hrs the plant was made safe and repaired.
The following day when the ammonia was delivered the plant was recharged ant set to work.
Lot's of good lessons were learned during the course of this for site and us.
One of which was had the engineer gone down the emergency ladder he would of probably broken his legs on the drop at the end as there were huge lumps of steel and pumps tacked underneath it!
My opinion is had this been allowed to escalate where the fire brigade and resultant media circus had attended.
Then it would of been blown out of all proportion and the resultant water certain used as standard practise by the fire brigade would of wreaked the plant for good.

They are no different from us and just as scared of ammonia as many others. there where guys spouting off about environmental issues etc whilst all this was going on.
Its amazing how a not so polite "Back Off" and "But Out" works, there ere guys complaining about the smell.
Who when told if its strong then walk away. Did not know where to put themselves!
Grizzly

al
23-02-2014, 08:45 PM
Fair points Grizz, good training and a calm attitude works wonders, well done!

RANGER1
23-02-2014, 08:57 PM
Grizzlly you mention internal corrosion, do I understand that correctly!

I have never head of it on any refrig system that's all, only external.

How do you get that respirator to seal on a beard?

Grizzly
23-02-2014, 10:17 PM
Grizzlly you mention internal corrosion, do I understand that correctly!

I have never head of it on any refrig system that's all, only external.

How do you get that respirator to seal on a beard?

Good point Ranger.
If you look at the photos again there is actually only external corrosion.
Come to think of it you need oxygen to activate rust don't you.
So please ignore the rantings and thanks for the correction.
As they say a good point well presented!

My beard is long gone, working in to many food establishments nowadays. I do so hate Snoods!

Al you and I agree on so much!
It's good to sound off from a practical point of view occasionally.

There are many that will tell you what you cannot do, not so many telling what you can and how nowadays.
Which is why this forum is so valuable.
Cheers guys.
Grizzly

Magoo
24-02-2014, 12:40 AM
Hi Grizzly.
a very good post, how much time was spent doing incident reports and paper work for all the Haschem nutters.

Grizzly
24-02-2014, 06:09 AM
Hi Grizzly.
a very good post, how much time was spent doing incident reports and paper work for all the Haschem nutters.

Thanks for the input my friend!
That's my point really, because control was established from the start.
The fire brigade and their chemical response teams etc. were kept out of the equation.

So all the Paperwork was minimised.

I dread to think how many would of crawled out of the woodwork otherwise.
Grizzly.

PaulZ
24-02-2014, 10:21 AM
Hi Grizzly
Very good post it's a pity the people who make all the noise don't read it and maybe ask advice from experienced guys before calling in the emergency services.
We had one recently and the whole lot turned up except the TV thank god.
And yes we had heaps of paperwork to do. I had to do the accident investigation and then we had a debrief what a joke.
The fire brigade wouldn't let anyone back into the building until the level had dropped to 5 ppm because of some rule where they multiply the reading they get by 10 so when they read 25 ppm on the meter they call it 250 ppm.
This whole incident was because 140 ml was let go.
I can't say too much but suffice to say the attendance by fire, ambulance and police was due to an over zealous person who chose not to ask the right people.
And I totally agree that if you have the right training and keep a cool head most emergencies can be dealt with safely without the need for the emergency services.
I have been involved in a few and like you I am still here.
Paul

Grizzly
24-02-2014, 05:53 PM
Brilliant reply Paul.
I have massive new site where a meeting was held between my colleague and I and the local Fire brigade.
They were interested in what we had to say and were relieved when I said
"Basically if no-one is inside, then stay out ensure that with the help and assistance of site security. A safety cordon is maintained, based upon the severity of the leak and of course the wind direction.
Adding that the plant would be totally isolated electrically, so unless personnel were in the path of the escaping Ammonia vapour.
Sit back and wait for us! Then we can all discuss what and how to proceed.
The Fire Officer I spoke to fully understood and likened my explanation to what they called a slow burn!
Either way we all agreed to access the situation as it developed and not a knee jerk reaction, which has happened before.
They would not have to wait long as when the level 2 alarm occurs it automatically dials the duty engineer anyway.
How many that spout off about safety and Ammonia realise that liquid Ammonia flashes off until the areas in contact with it have no-more heat differential to give.
Meaning a burst pipe flooding a plant room floor will, set off the alarm as the heat is taken out of the concrete.
Resulting in initially large amounts of vapour.
Once the concrete reaches -33c, which is not long with ammonia. You are left with a slightly smelly plant room full of what looks like clear water. But in fact is actually liquid ammonia!
I know I have been there.
If some Person decide to spray water on this standing liquid without knowing what and how to do it. All Hell lets loose.
However if dealt with carefully it is easy enough to recover from that situation, without further incidents!

I agreed that we are preaching to the converted, but sensible words do leak out and hopefully a few reach the correct ears?

Take care my friend.
Incidentally I know of no-one being killed by Ammonia, whereas there was 4 engineers killed 2 years ago in one incident alone concerning *****s! (In the UK!!!)
Says it all really doesn't it!

Grizzly

HVACRsaurus
24-02-2014, 09:13 PM
All good information guys.

I went to a call once - six engine response, HAZMAT team, mobile command (whole box & dice)

Problem, faulty detector.

PaulZ
25-02-2014, 12:00 AM
HVAC
Thats the problem with the detectors connected directly to the fire panel. Did the client have to pay, normally they have to if it's a false alarm.
Grizzly
From memory I can only recall 1 fatality here and that was a long time ago, a plant operator trying to do what he thought was the right thing for the company and paid the ultimate price. You know when ammonia is around and as I have said to the younger mechanics treat it with respect and don't become complacient, has worked for me.

Paul

Magoo
25-02-2014, 01:00 AM
Hi Grizzly.
a good resolve to problem with a cool head and sound experience. Comes with age.
I compliment you for practical discussions and instruction advise with local Fire Service. More should be involved with actual people that service and maintain systems.
Suggest you publish an article along those lines and forward to the relevant public response services people.

HVACRsaurus
25-02-2014, 06:50 AM
Paul, I didn't find out if they had to pay, likely you are right. Maybe I should have loosened a valve gland so they wouldn't have to ;)

Tycho
28-02-2014, 05:23 PM
How many that spout off about safety and Ammonia realise that liquid Ammonia flashes off until the areas in contact with it have no-more heat differential to give.
Meaning a burst pipe flooding a plant room floor will, set off the alarm as the heat is taken out of the concrete.
Resulting in initially large amounts of vapour.
Once the concrete reaches -33c, which is not long with ammonia. You are left with a slightly smelly plant room full of what looks like clear water. But in fact is actually liquid ammonia!

Incidentally I know of no-one being killed by Ammonia, whereas there was 4 engineers killed 2 years ago in one incident alone concerning *****s! (In the UK!!!)
Says it all really doesn't it!

Grizzly

Well said, including the comment about people freaking out about the smell :) "Well if you can't handle it, step away and let me do my job in controlling it then"

There was an incident in my area a few years back where a technician was to drain oil from the pilot receiver level indicator. the indicator pipe was fitted with a danfoss SNV valve, and the valve was blanked off with a 10mm ermeto buz (or blanking plug), these are known to hang/stick when you loosen the nut, so you should loosen the nut a few turns and give it a tap to unseat it so you are sure the valve isn't leaking before you remove the nut and blanking plug completely.
In my case, I always check if the valve is closed before I think about loosening the nut and plug.

Anyways, I don't know first hand, but after piecing together many different stories I gather that the person took the nut of, and then gave the blanking plug a rap with his spanner to get it to unseat, unfortunately the snv valve was full open and out came 8-10 bar with liquid ammonia.

The guy managed to get out and put his mask on, tried to get back in to close the valve, but according to the site engineer he had to turn back, firstly because the filters of the mask were overloaded and he couldn't pull any air in and second because various places were burning to badly when entering the fog :)

The plant shut down as it should, but ammonia was still pouring out and they didn't have full body kits on site yet so the fire dept was called.

They didn't know the plant so the site engineer was donned out in a full body kit with oxygen tanks to accompany the fire dept inside, acting as a guide.

here is where the fire dept made a blunder, they used water fog to suppress the ammonia fog, thereby boiling off more of the ammonia that was floating on the floor, causing even more fog, they didn't have inter suit communication, and the site engineer told me he knew the location of the valve (straight forward from the door) and he fumbled his way there and located it by sound and feel...

However the firedept kept dousing him in water, so when he had the valve closed and was ready to leave his feet were frozen solid to the water/ammonia mix on the floor and with no communication he couldn't tell anyone that he couldn't move, and he kept pointing at his legs to get to hose guy to direct the water at his feet and the hose guy was just nodding and pointing to the door :)

He got the point through at last though :)

*edit*
No injuries apart from some dents to their pride
*edit*

Grizzly
28-02-2014, 06:55 PM
Interesting if a little scary.
Its amazing how many undo Ermeto caps without checking the valve is correctly shut.
Ermeto = (Hydraulic fittings favoured my many, like Grasso, Sabroe, Frick and many others!)
The problem is people do them back up to tightly having removed them in the first place.
The 2 spragged points on the end of the plug are then rolled flat as the outer locking ring is undone.

Having confirmed the valve is shut, if when you undo the outer nut the plug is not withdrawn with it.
Tighten it back up enough so that you can get some purchase around the errant plug with either a set of mole grips or water pump type pliers.
Grip pliers tightly and with the other hand slacken the locking ring, which as it screws off of the threads will
come up against the inside edge of the pliers / grips.
Further undoing of the nut should then withdraw the plug also.

This method is kinder than just slackening the locking ring and graunching the olive and plug.
Plus would anyone want to be swinging on the plug unnecessarily?

You do sometimes have to use some brute force, but mostly the plugs can be teased off!
Thanks for the input tyco, Myself and I am sure many others will have learnt from it.

I can imagine the teasing that engineer got!

Hey! like I said we are all cautious and rightly so.


Brilliant all the same!
Grizzly

Tycho
28-02-2014, 07:46 PM
Interesting if a little scary.
Its amazing how many undo Ermeto caps without checking the valve is correctly shut.
Ermeto = (Hydraulic fittings favoured my many, like Grasso, Sabroe, Frick and many others!)
The problem is people do them back up to tightly having removed them in the first place.
The 2 spragged points on the end of the plug are then rolled flat as the outer locking ring is undone.

Having confirmed the valve is shut, if when you undo the outer nut the plug is not withdrawn with it.
Tighten it back up enough so that you can get some purchase around the errant plug with either a set of mole grips or water pump type pliers.
Grip pliers tightly and with the other hand slacken the locking ring, which as it screws off of the threads will
come up against the inside edge of the pliers / grips.
Further undoing of the nut should then withdraw the plug also.

This method is kinder than just slackening the locking ring and graunching the olive and plug.
Plus would anyone want to be swinging on the plug unnecessarily?

You do sometimes have to use some brute force, but mostly the plugs can be teased off!
Thanks for the input tyco, Myself and I am sure many others will have learnt from it.

I can imagine the teasing that engineer got!

Hey! like I said we are all cautious and rightly so.


Brilliant all the same!
Grizzly

He didn't get teased, but he was a master of refrigeration in his own mind and left to work on bigger things and not the playschool systems that we were dealing with (according to himself) a few months later :)

I had my scare 18 years back when I trusted a site engineer when he said that he had pumped down the whole system and that all the pipes were closed, then my co-worker (who was then my teacher) went on to cut the hotgas return pipe on the wrong side of the valve, and had a blowout from the liquid separator (the main return valve was open) luckily we were the only ones on the ship, and we took turns holding our breath and running down to close a few turns on the main return valve (R22 btw) before running back up to the trawl deck to catch some breath.
When we finally got it closed and ran back down to start the engine room exhaust fans, they tripped on high current because there was too much ***** and we had to keep running down while holding our breath every five minutes to reset the trip switch on the exhaust fan...

That was 17-18 years ago, and that was also the last time I trusted anyone but myself when it comes to if a system is closed off and without pressure.

What I normally do on these plugs ( as long as they look to be in good condition) is to loosen the nut a turn or two, then give the nut a tap or two with the spanner to see if the plug comes out, if it doesn't, I have to get the pliers out and wiggle it free.

one thing I have seen in south america is that these plugs have two grooves punched into the side of the neck, so that if you loosen the nut more than a turn or two, the nut will hit the groove and pull the plug out along with it.

It's something I want to incorporate in our company, because it's a cheap thing to prevent accidents.

I have never seen these kind of plugs in europe, but in South America they come pre assembled with the plug stuck to the nut

Tycho
28-02-2014, 08:38 PM
Interesting if a little scary.
Its amazing how many undo Ermeto caps without checking the valve is correctly shut.
Ermeto = (Hydraulic fittings favoured my many, like Grasso, Sabroe, Frick and many others!)
The problem is people do them back up to tightly having removed them in the first place.
The 2 spragged points on the end of the plug are then rolled flat as the outer locking ring is undone.

Having confirmed the valve is shut, if when you undo the outer nut the plug is not withdrawn with it.
Tighten it back up enough so that you can get some purchase around the errant plug with either a set of mole grips or water pump type pliers.
Grip pliers tightly and with the other hand slacken the locking ring, which as it screws off of the threads will
come up against the inside edge of the pliers / grips.
Further undoing of the nut should then withdraw the plug also.

This method is kinder than just slackening the locking ring and graunching the olive and plug.
Plus would anyone want to be swinging on the plug unnecessarily?

You do sometimes have to use some brute force, but mostly the plugs can be teased off!
Thanks for the input tyco, Myself and I am sure many others will have learnt from it.

I can imagine the teasing that engineer got!

Hey! like I said we are all cautious and rightly so.


Brilliant all the same!
Grizzly

I just noticed you mentioned the two spragged points on the plug, these are not common in europe or at least not in Norway.
we get the plugs and the nuts separately and there are no sprags on the plug that pulls the plug out when you loosen the nut, that was the problem in my initial story, the plug had been over tightened, he removed the nut completely instead of doing a few turns and then he tapped the plug with his spanner and HP liquid from the receiver was sprayed on the floor.

I don't like to keep swinging at the plug as you say :) if it is a rusted fitting I would shy away from it, but in this case it was a new system and everything was brand spanking new :) and shiny :)
had it been rusty, I guess this guy would have loosened it a little bit and then used his pliers on it :)



In my mind, his biggest error was in not checking if the valve was closed...

it is something I always do, I always check if the valve is closed, if I have checked it the day before when I left the site, I will check it again when I come to site the next day before I do any work.

And I have a mantra that I keep repeating to the young'uns and apprentices, it's a mantra I follow myself, I may get funny looks sometimes, I keep telling them "no matter what you are going to do to an ammonia system, put your mask on, it may be cumbersome and in the way, but it provides you with a full face shield, and you have filters on it that gives you a chance to get away" they ask me how many times I have been saved by my mask, and honestly, I say, filterwise, probably none, but the eye shield, probably a hundred times" How many times I have opened a danfoss valve and have ammonia "squirt" out of the tiny hole in the cap, that seems to somehow always be pointed at your face when you open it, I can not count :)
But I tell them to not be afraid of ammonia, respect ammonia and be aware of the dangers it poses.
Don't wear the gas mask because ammonia is dangerous and will explode in your face, most of the time you have evacuated the system so good that you don't need a mask because of the smell... but you don't wear a mask only to protect from the smell, you also wear it to protect your eyes...

I tell my people "You don't wear the mask because you will always have a problem with ammonia, you will get used to the smell, you will be able to work without a mask in a room full of ammonia, where other people will go "dear good, we're all gonna die" you will be going "wth, stings a bit, but that's all" then you will shake your head at the worry warts that just ran out of there.

So I tell them "you don't wear your mask because you are working with ammonia, you don't wear your mask because everyone else says it's the right thing to do, you don't wear a mask because ammonia is going to kill you, you don't wear a mask because everything is going to go wrong when you open a ammonia system!"

"but why do we even put our masks on then"??? Because we get used to the fumes, we can work in the compressor rooms when it smells like ammonia"

"Yeah, you don't wear your ammonia masks because it is always going to go wrong, you wear your masks for the one time it does go wrong, the one time the masks protects you from getting a splash in your eyes, and the one time you do get a blowout and you need to get out of there, and having your "respirator" on gives you enough time to get out

we have had two engineers spend a week in hospital with water drips in their eyes, both before my time (wich means over 18 years ago), one of them is our main sales guy, and he said " I was standing there, draining ammonia into a bucket of water (it was legal back then), when the hose bucked, and I could see this tiny drop of water, flying up towards my eye, and I thought to myself, I should close my eyes, and then the !"#%!!! drop hit me straight in the eye before I managed to close it, and I spent a week in hospital with my eye forced open and force dripped with saline water, I couldn't blink, I couldn't sleep, my eye was always open and with a blurry view of the world...

Rob White
03-03-2014, 09:31 AM
.

I don't know if this will help but the IOR raised this issue a few years ago.

See

http://www.ior.org.uk/app/images/pdf/GN%2022%20valve%20safety%20alert%20(May%202011).pdf

Regards

Rob

.

Grizzly
03-03-2014, 06:10 PM
.

I don't know if this will help but the IOR raised this issue a few years ago.

Thanks Rob.
I also read that when it first came out.
I think I even remember which site it was about?

Grizzly

Tycho
22-04-2014, 07:30 PM
Found one of my own last week, luckily it was before "it came off in my hand Guv" :)

Danfoss blacksteel SNV 8 in a Stainless socket on a stainless pipe
11430

Superfridge
25-04-2014, 07:02 AM
Ask your fireman who is going to walk into an NH3 cloud if their suit is rated to cope with the possible -75 degC encounted when NH3 is in aerosol form and I bet you will get a blank look and a hesitant fireman.

RANGER1
25-04-2014, 11:00 AM
Ask your fireman who is going to walk into an NH3 cloud if their suit is rated to cope with the possible -75 degC encounted when NH3 is in aerosol form and I bet you will get a blank look and a hesitant fireman.

Out of interest, why would ammonia be a possible -75 deg C!

Tycho
25-04-2014, 07:41 PM
Out of interest, why would ammonia be a possible -75 deg C!

The melting point for ammonia is -77C and the boiling point is -33C, if you have a release of for example HP ammonia liquid to atmosphere, it will reach the melting point temperature.

I couldn't find any literature about it, but a catastrophic failure of a HP liquid pipe where lots of liquid flashes to gas, it will reach the melting point temperature.

Superfridge
25-04-2014, 10:24 PM
Out of interest, why would ammonia be a possible -75 deg C!

Sorry I made a mistake, it's -74 degC;).

I have just read through some YORK NH3 training info from many moons ago and it say's

"Few people are familiar with the aerosol phase; however this may be the most dangerous phase of all and the one hardest to handle. The small droplets of R717 draw heat from themselves and the surrounding environment and, contrary to common expectations, temperatures right down to -74 degC can be measured"

There is a graph showing Ammonia in air on a Psychrometric chart at 1 bar. At 20 degC the resulting temp at 100% saturated NH3/air is -74 degC.

Grizzly
25-04-2014, 11:10 PM
The melting point for ammonia is -77C and the boiling point is -33C, if you have a release of for example HP ammonia liquid to atmosphere, it will reach the melting point temperature.

I couldn't find any literature about it, but a catastrophic failure of a HP liquid pipe where lots of liquid flashes to gas, it will reach the melting point temperature.

Sorry but you are scare mongering and talking rubbish.
I have personally walked through a plant room which was flooded with liquid ammonia, wearing BA and a Chemical suit.
And that was real life not some Lab!

Once all the surfaces are down to Atmospheric Pressure/temp that's it.
IE -33c!!!
What's this melting point rubbish?
I have been next to a punctured ammonia line and it Flashes off at a huge rate right enough.

However I did not see any melting! Plenty of liquid fear from some.
Grizzly

RANGER1
25-04-2014, 11:21 PM
I can only find melting point of ammonia as like ice to water, frozen ammonia turning to liquid ammonia.
I will have to find out more, as cannot see it happening in our world
I have heard it suggested adding liquid ammonia into a plant under a deep vacuum can have similar effect, but never been a problem that I have heard about damaging pipe or equipment.

Tycho
28-04-2014, 11:47 PM
Sorry but you are scare mongering and talking rubbish.
I have personally walked through a plant room which was flooded with liquid ammonia, wearing BA and a Chemical suit.
And that was real life not some Lab!

Once all the surfaces are down to Atmospheric Pressure/temp that's it.
IE -33c!!!
What's this melting point rubbish?
I have been next to a punctured ammonia line and it Flashes off at a huge rate right enough.

However I did not see any melting! Plenty of liquid fear from some.
Grizzly

Yes, *waves hands around and mutters voodoo* woooo woooo scaremongering and spooky stuff because you have waded around in liquid ammonia, nothing I say can be true, and that liquid ammonia was exactly -33 degrees, because you had a thermocouple with you and measured the temperature all around as you were wading around in liquid ammonia... Never mind science :D

Maybe superfridge said it better than me, but when ammonia is in droplet aerosol form in a state of decompression, the liquid droplets draws heat from themselves and they reach the temperature of -77,7 below that temperature in atmospheric pressure ammonia turns to a solid, but since it's in decompression and drawing heat from itself and the surrounding, the liquid is at -77,7 degrees centigrade...

sure, when it's just floating around on the ground stabilized it will be at -33C, but walk into a spray of liquid ammonia and you would be in a whole other world...
I'm not talking about melting, I'm saying ammonia below -77C at atmospheric pressure would become a solid as soon as it drops below that temperature however, as it draws heat from itself and the surroundings it stays liquid and gaseous but the temperature of the liquid aerosol spray is at -77C

I'm sorry, but I can't break the laws of physics to agree with you :)

Just because you haven't seen it doesn't mean it isn't so ;)

*makes magic voodoo hand gestures* Science b***h

Tycho
28-04-2014, 11:49 PM
By the way, what is melting?


Melting is turning from a solid to a liquid, so of course you didn't see any melting :)

RANGER1
29-04-2014, 08:01 AM
Tyco, super fridge how can I make this happen in a test?

what pressure liquid ammonia, is it sub cooled or anything special?
Any particular velocity or leak size.

What atmospheric conditions would I require, outside or in a freezer.

I'm not trying to be smart, but trying to understand it without reinventing the wheel.
Why would a phenomenon like that be replicated within a running system!

Tycho
30-04-2014, 04:11 PM
Tyco, super fridge how can I make this happen in a test?

what pressure liquid ammonia, is it sub cooled or anything special?
Any particular velocity or leak size.

What atmospheric conditions would I require, outside or in a freezer.

I'm not trying to be smart, but trying to understand it without reinventing the wheel.
Why would a phenomenon like that be replicated within a running system!

I'm still trying to find any literature on it that really explains it.

The small tidbits I have picked up and read says that ammonia in a liquid/aerosol form will draw heat from itself as well as the surroundings, causing the temperature to drop below the boiling point of -33C and reach a temperature close to the melting point of -77.7C.

so on that account, I'm guessing it should be possible to use a temperature probe in a spray of ammonia aerosol, As with everything in refrigeration and refrigerants I'm also guessing it needs a certain pressure drop down to atmospheric pressure. I don't think it would happen with a release to atmosphere from a LP liquid line :)

I'm also guessing that it would certainly happen when charging a system at deep vacuum and I intend to test this when I next charge a system.
We have had cases on some of our RSW systems, where the charging valve is at the bottom of the chiller level indicator, where the level indicator (Danfoss AKS 41) has been broken after charging the system.
Noticeable on most of them were that the bottom of the teflon/white covering was bulging out

sterl
30-04-2014, 07:29 PM
The basis for boiling point is the saturation pressure of the refrigerant. Saturation is achieved in a closed container where the vapor and the liquid phases are in equilibrium. Thus the pressure of a cylinder of refrigerant, or propane, or any other compressed volatile, will vary with the temperature according to the sat chart....

Add another gas, you get partial pressures in the vapor phase. Thus mixtures of refrigerants yield vapor pressures different from either of the parent components.

And if you make a puddle of ammonia and let it basically sit still, the open space immediately above the puddle will head toward being 100% ammonia vapor. Before it gets there, the temperature of the liquid in the puddle will dip below the boiling point of the refrig because the vapor pressure above the liquid is a partial pressure of ammonia, the rest of it being air pressure. Obviously, that partial pressure is lower than atmospheric. How far it dips depends on the agitation of the gas mix immediately above the puddle, the temperature of the "second" gas and the heat capacitance and heat transfer from the "bottom" side of the puddle. Which means that if your puddle resides on top of 200 mm of concrete floor and the air is basically still above the puddle, the whole assembly drifts slowly down to minus 33 C and basically parks there....

If you want to: try it with a little refrigerant in a pyrex pie plate sitting on top of a slab of insulation. Keep it out of the breeze, it will probably go to minus 37 or 38 C. Fan it with fresh air for a few seconds and the temperature will dip, each time you agitate it.

The jet of flashing liquid thing is accurate though difficult to reproduce. The low temperature front will be near the outer edge of the "definitely wet" portion of the spray. I have done this with butane; some practical limitations to trying to do it with ammonia.

And yes: You can do some very quick damage to portions of a circuit by running "first fill" as liquid to an otherwise warm and deeply vacuumed space. Our procedures call for the vacuum to be broken with vapor from the corresponding portion of circuit or tanker or cylinder. One of the procedures that always gets me is the folks who furnish condensing units with the charge in the HP receiver....Lots of liquid solenoid valves get damaged when the liquid line gets opened up to 100-micron vacuum.

RANGER1
01-05-2014, 12:18 PM
http://m.youtube.com/watch?v=BTskwWUE6Yk




This is what I found but don't really understand it at the moment on low temp ammonia

Magoo
02-05-2014, 02:02 AM
Thanks Ranger1.
very interesting result after removing probe from liquid.

RANGER1
02-05-2014, 10:54 AM
Thanks Ranger1.
very interesting result after removing probe from liquid.

https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Boiling_point.html

This seems to explain it fairly well, so not really a standard refrigeration system scenario.

When opening go to bottom & open to full version of explanation.

Learn something new every day or two!

Magoo
03-05-2014, 02:01 AM
Cheers Ranger1 .
always up for learning something new.

Superfridge
06-05-2014, 10:45 AM
I found the YORK manual on line, page 5 shows the Psychrometric chart. It looks much like the dew point temperature you would see on the charts we are used to.

http://iornw.org.uk/downloads/ammonia1.pdf

RANGER1
06-05-2014, 09:54 PM
I found the YORK manual on line, page 5 shows the Psychrometric chart. It looks much like the dew point temperature you would see on the charts we are used to.

http://iornw.org.uk/downloads/ammonia1.pdf

nice info super fridge thanks

Tycho
28-05-2014, 05:42 PM
Good information all around :)


as a reward, here is another valve I removed from the same system as above.
After replacing this we went over the whole system to check for any other "disasters waiting to happen"
11535