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lraja
12-01-2008, 03:09 AM
According to IIAR, the safety valves of ammonia refrigeration installations need to be checked annually for proper functioning. Do these valve have to be replaced after say 5 or 10 years service regardless they function properly ?. If this is in regular refrigeration practice, what are the related regulation or standard?

thanks

raja

NH3LVR
12-01-2008, 04:09 AM
Hi Raja;
We have allways followed the practice of changing them out after 5 years. I have never heard of testing them yearly. (Unless it is just a visual inspection)
It would not be effective by any standard. Valves that have opened once can be a source of leakage. Makers recommend that you change the valve after a release.

NH3LVR
12-01-2008, 06:05 AM
I also should have mentioned the need to check reliefs for seepage on a regular basis.

Grizzly
12-01-2008, 12:47 PM
Hi Raja;
We have allways followed the practice of changing them out after 5 years. I have never heard of testing them yearly. (Unless it is just a visual inspection)
It would not be effective by any standard. Valves that have opened once can be a source of leakage. Makers recommend that you change the valve after a release.

I could not of put it better myself.
Here in the UK / EU it is a legal requirement (Pressure Vessel Regs) to remove PRV's and have them Indepedantly tested proved and calibrated. With a certificate provided, dated and numbered to each specific valve every 5 years. Each valve also is tagged with the date tested and the relief pressure it is set to.
A log or file is kept with the valve details in which are inspected yearly by the Insurance Companies (whoever provides Insurance for the plant) own Engineering Surveyor.
Most sites have by now had duel valve manifolds fitted to enable the safe isolation of 1 of the 2 valves, prior to having the afor test and certification carried out.
Dual valves allow you the benifit of being able to rotate the valve calibration whilst still running the plant.
May I just add so as to not confuse not all prv's have to be periodically tested. It depends where in a system and what they are protecting, also the size of the equipment is relevant.
Many Chillers and smaller plant have prv's that
don't apply. Also these PRV's have to be vented to atmosphere and not into any area's where personnel could be affected should they open! But that another set of rules to consider.
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

lraja
12-01-2008, 01:02 PM
'check' in the first post mean visual inspection, sorry if that mislead you. Thank you all for the replies

raja

yusuf amur
12-01-2008, 09:41 PM
change it after released ,only not for regulation olso for your safety precosion but dont forget to clean and service the condesor becouse high pressure couses to blowup savety valve.

yusuf amur
12-01-2008, 09:42 PM
change it after released ,only not for regulation olso for your safety precosion but dont forget to clean and service the condesor becouse high pressure couses to blowup savety valve.

Josip
13-01-2008, 01:50 AM
Hi, all :)


I could not of put it better myself.
Here in the UK / EU it is a legal requirement (Pressure Vessel Regs) to remove PRV's and have them Indepedantly tested proved and calibrated. With a certificate provided, dated and numbered to each specific valve every 5 years. Each valve also is tagged with the date tested and the relief pressure it is set to.
A log or file is kept with the valve details in which are inspected yearly by the Insurance Companies (whoever provides Insurance for the plant) own Engineering Surveyor.
Most sites have by now had duel valve manifolds fitted to enable the safe isolation of 1 of the 2 valves, prior to having the afor test and certification carried out.
Dual valves allow you the benifit of being able to rotate the valve calibration whilst still running the plant.
May I just add so as to not confuse not all prv's have to be periodically tested. It depends where in a system and what they are protecting, also the size of the equipment is relevant.
Many Chillers and smaller plant have prv's that
don't apply. Also these PRV's have to be vented to atmosphere and not into any area's where personnel could be affected should they open! But that another set of rules to consider.
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

In my country (Croatia) we do not need to replace PRV valves after some years, they can be permanently installed, but every year (if they open or not) we have to dismantle one PRV (usually they are two-for safety reasons, on the same exchange stop valve) make a complete visual inspection and then recalibrate according to system and reinstall again...the same procedure with another one and of course with all installed on the plant (this can be done only by authorized services and all is covered with proper documentation, tags)....otherwise authorities will come and shut down your plant and send you a big fine:eek:

Valid for all PRV-on ammonia, *****s, water vapour....they are there to protect life.....REMEMBER, SAFETY SHOULD BE A LIFE ATTITUDE


Best regards, Josip :)

IceMan_4000
25-01-2008, 09:16 PM
I also should have mentioned the need to check reliefs for seepage on a regular basis.


That is what Rupture disks are for. I always install one under my valves. A simple gauge displays if a valve should be replaced, Because it has seepage or has lifted

And in Canada it is every 5 years according to the B-52 code

Billy Ray
26-01-2008, 12:00 AM
Hi Mr Iceman 2000,

Do you have any problems with rupture discs on hot receivers.

1.I have had problems mysely with them de-rating due to heat?

Can you tell me how you pressure test in your fine land? We pressure test in the UK to EN378 standard, which relates to 55 deg SCT X 1.1 (for any particular refrigerant). We strength test to 55 deg SCT X 1.3.

Billy Ray
26-01-2008, 12:03 AM
Hi Mr Iceman 2000,

Do you have any problems with rupture discs on hot receivers.

I have had problems mysely with them de-rating due to heat?

Can you tell me how you pressure test in your fine land?
We pressure test in the UK to EN378 standard, which relates to 55 deg SCT X 1.1 (for any particular refrigerant). We strength test to 55 deg SCT X 1.3.
(kind regards to Tony).


What's your standard?

Billy Ray

Grizzly
26-01-2008, 12:42 AM
Guys.
Further to my posts I have been asking questions.
It would appear that the minimum requirement is every 5 years.Or less if deemed necessary by the originator of the required written scheme.
Usually the originator is employed by the Insurance Company. If the user or owner has Insurance, this is not mandatory. But having a written scheme (as defined by the HSE.) PRESSURE SYSTEMS SAFETY REGULATIONS 2000 IS MANDATORY.
What type of typical pressurised system might require a written scheme of examination?
quote "A vapour compression refrigeration system where the installed power exceeds 25kw"
I have yet to confirm what "Installed power" actually means?
But suffice to say at 25kw there are an awfull lot of chillers etc with PRV's ( within UK.) THAT SHOULD BE RECALIBRATED EVERY 5 YRS!
Makes interesting reading dosen't it! Just think of all that extra work removing & replacing the single manifold Prv's etc etc.
IF MY INTERPRETATION OF THE WRITTEN FACTS IS CORRECT.
All the quoted facts are straight from the Health and Safety Executive as listed below. (first link on page...pdf to big to post!)
Hope this helps Grizzly
http://www.google.co.uk/search?hl=en&q=HSE+Pressure+Systems+Safety+Regs&meta=

Grizzly
26-01-2008, 01:03 AM
Billy Ray
It's no longer 3078 is it as my post "What pressure do I test to" proves, is it?


That is what Rupture disks are for. I always install one under my valves. A simple gauge displays if a valve should be replaced, Because it has seepage or has lifted

And in Canada it is every 5 years according to the B-52 code
Iceman 4000
What you suggest is not allways possible.
As an indicator some of the guys have suggested a condom sealed over the Relief side of the prv. And much humourous discussion has been had by all since.
My solution wich I have not seen posted before is to seal the Relief side of the valve with a generous plug of GREASE. Which you will find will indicate any gas/ vapour seepage, particularly if you wipe across the face of the valve. With a straight edge creating a clean blemish free surface. Perfect for indicating any sort of Gas movement through the valve.
Be carefull though as not all greases are "Stiff" enough to counteract the gravitational fources.
So a little trial and error may be necessary. But once you find a grease capable of remaining in possition. You have a very cheap and reliable bursting disk / leak indicator.
Which won't upset your partner when she finds a tub of grease and not a supply of condoms!
( sorry I couldn't resist I pun! )
Cheers Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

TXiceman
26-01-2008, 04:43 AM
I believe you will find the 5 year check/change requirement creeps in with the mention of IIAR standards in the written Hazop procedures or RMP for a plant. I do not believe there is a national standard which requires this time frame.

If a city/county or local code has adopted IIAR, you will have to do the 5 year thing.

Ken

IceMan_4000
26-01-2008, 06:30 AM
Billy Ray
It's no longer 3078 is it as my post "What pressure do I test to" proves, is it?


Iceman 4000
What you suggest is not allways possible.
As an indicator some of the guys have suggested a condom sealed over the Relief side of the prv. And much humourous discussion has been had by all since.
My solution wich I have not seen posted before is to seal the Relief side of the valve with a generous plug of GREASE. Which you will find will indicate any gas/ vapour seepage, particularly if you wipe across the face of the valve. With a straight edge creating a clean blemish free surface. Perfect for indicating any sort of Gas movement through the valve.
Be carefull though as not all greases are "Stiff" enough to counteract the gravitational fources.
So a little trial and error may be necessary. But once you find a grease capable of remaining in possition. You have a very cheap and reliable bursting disk / leak indicator.
Which won't upset your partner when she finds a tub of grease and not a supply of condoms!
( sorry I couldn't resist I pun! )



Hey Grizzly I do not understand why this is not possible. saftey should not be an Item that can not be done all the time.

even in the ***** Freddy world, actually especially since the costs of these refrigerants is sky rocketing.

Personally I am a NH3 man and I am very preticular about how are systems are protected

You will have to copy paste this for yourself I do not have 15 posts yet.

www"DOT"hantech"DOT"com/documents/PDF/K209.pdf
(replace "DOT" with ".")

I used ballons for years as an apprentice mechanic. but for a true measurment on releif leakage or valve life protect on the down stream side not the upstream.


Check out that PDF even my sister company (The commerical side of Refrig) is starting to ask us how to properly use Safety releif devices to prevent loss thier very expensive refrigerants

koelie
28-01-2008, 09:12 PM
There are systems with an interlock key on a double relief valve, so one relief valve can be removed, and be sure the other one is open.

Grizzly
29-01-2008, 12:21 AM
Hey Grizzly I do not understand why this is not possible. saftey should not be an Item that can not be done all the time.

even in the ***** Freddy world, actually especially since the costs of these refrigerants is sky rocketing.

Personally I am a NH3 man and I am very preticular about how are systems are protected

You will have to copy paste this for yourself I do not have 15 posts yet.

www"DOT"hantech"DOT"com/documents/PDF/K209.pdf
(replace "DOT" with ".")

I used ballons for years as an apprentice mechanic. but for a true measurment on releif leakage or valve life protect on the down stream side not the upstream.


Check out that PDF even my sister company (The commerical side of Refrig) is starting to ask us how to properly use Safety releif devices to prevent loss thier very expensive refrigerants
Iceman.
Are you still on the tools or are you sales your profile dosn't say.
I AM OFFENDED BY YOUR EVEN IN THE "FREDDY ***** WORLD".
For 2 reasons, firstly there are a huge amount of very very good engineers on this forum that don't work on ammonia. But they tollerate those of us that do!
Secondly if you were aiming your comment at me (because I did not whole heartedly agree with your " they should be fitted everywhere" policy).
I would like to point out that if you read some of my other post or read my profile. You would realise that I am qualified to comment on Ammonia or *****s.
My comment meerly was based on 30 odd years experiance as an engineer and realising that in the present economic climate.IT IS GETTING VERY VERY HARD TO CONVINCE ANYONE TO SPEND MONEY! No matter how well intentioned. ( In fairness to you that's a nice bit of kit shown on the pdf.)
There is a huge wealth of experiance on this site.
I for one am greatfull that others tolerate us "Stinkies" Gary's knickname for Ammonia Engineers,
don't you just love it
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon8.gif

IceMan_4000
29-01-2008, 01:44 AM
Grizzly first off I am sorry you took it that way. My comment to was just I did not understand a situation were Safety could not be done.

I was not throwing stones at you Grizzly I have read several of your posts since I have joined, and I usually find my head nodding along with you. You are a true wealth of knowledge on these boards

No offence was intended in the ***** Freddy comment. I just notice that PRV's are less prevelant then in the Stinkies side of it. When it comes to reliefs I am lucky, I have a nice goverment document called the the "B-52" that I can use to force my customers to spend money on a complete relief header like that.


So I whole heartedly say sorry to anyone that took offence.


I was just saying Saftey is not only our jobs it is our lifes. That is why I do not get were it can not be done. regardless of wich wrench is turning the bolts ***** or Nh3

To answer your question about my position, I am now in sales but that still does not stop me from the tools In fact today I have been on I high head call due to the -47c today. And as a sales dork I get the price objection all the time, that is were the sales skills and the ocational goverment document come into play.


Iceman_4000;)

Grizzly
29-01-2008, 07:54 PM
Grizzly first off I am sorry you took it that way. My comment to was just I did not understand a situation were Safety could not be done.

I was not throwing stones at you Grizzly I have read several of your posts since I have joined, and I usually find my head nodding along with you. You are a true wealth of knowledge on these boards

No offence was intended in the ***** Freddy comment. I just notice that PRV's are less prevelant then in the Stinkies side of it. When it comes to reliefs I am lucky, I have a nice goverment document called the the "B-52" that I can use to force my customers to spend money on a complete relief header like that.


So I whole heartedly say sorry to anyone that took offence.


I was just saying Saftey is not only our jobs it is our lifes. That is why I do not get were it can not be done. regardless of wich wrench is turning the bolts ***** or Nh3

To answer your question about my position, I am now in sales but that still does not stop me from the tools In fact today I have been on I high head call due to the -47c today. And as a sales dork I get the price objection all the time, that is were the sales skills and the ocational goverment document come into play.


Iceman_4000;)
Nice reply Iceman.
Having read it I now feel that I may have been as they say "a little harsh" in my reply.
It's sometimes hard to gauge how the post is intended. Sadly I have yet to learn to step back as much as some of the old timers do.
That having said I do have several questions / comments which are!
You say that there arn't as many valves used on ***** systems maybe! jury is out on that one. But surely we are at cross purposes on this one.
I am not nor ever will not doubt the need for PRV'S and their upkeep and maintenance thereoff.
What I am saying is how do you justify on safety grounds the fitting of a bursting disc / telltale valve.
Especially to a perfectly sound system / PRV.
The other objection I have is that it is a requirement in UK (can't speak for other parts). That all PRV'S be piped to atmosphere to prevent any personel being exposed to released refrigerant gasses. So to modify an existing system, time and extra exspence would have to be costed for. To accomodate the modifying of the ventline pipework.
So in short I whole heartedly agree with your suggestions with regard to new build and I like the equipment you have shown us. But have difficulty justifying a retrofit. Unless of course leaking PRV'S are suspected as a problem!
You must have a very good case for *****s where the valve are fitted outside, it's a hell of a job to leak test outside. Mind you a dab of grease can give a very good indicator. Given you can smell Ammonia at a concentration of 5 ppm, you can normally tell if a valve has been leaking.
At -47 why would anyone want refrigeration ouch!
What does a "High Head" mean?
Welcome to the forum and I look forward to your posts in future.
Grizzly http://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

IceMan_4000
29-01-2008, 08:35 PM
1.
At -47 why would anyone want refrigeration ouch!

Becasue we heat the space for people. people do not melt Ice does.

2.
What does a "High Head" mean?

High compressor discharge.


-47 means service calls due to compressors with high head.

at that low temp the ammonia walks itself on up to the condser. due to the lower pressure outside in the condenser compared to in your evaporator.

Soliquid in the condenser that has a vapor locked metering device=High Head


Thank you Grizzly for the welcome aboard

I look forward to typing them

Iceman_4000

US Iceman
29-01-2008, 09:46 PM
Nice to see everyone is getting along well.;)

The idea of using rupture disks could be argued on the basis of how the system was designed. You have to remember relief valves are factory set for a specific pressure, but this pressure setting has a tolerance. In effect, the relief vales can start to weep before the the set pressure is reached. This is where the use of rupture disks can help to minimize the weeping of relief valves.

At the same time, you should be aware the rupture disks also have a tolerance to their design rupture pressure (although it can be similar or less than the relief valve tolerance, depending on the quality of the rupture disk itself).

Now at this point we should ask ourselves something important... If the pressure is high enough to cause the relief valves to weep....why is the pressure that high to start with?:confused:

It's also important to recognize the use of rupture disks under relief valves will require a re-rating of the relief valve capacity itself.

This affects the required "corrected" valve capacity and can also affect the vent line piping design. The adequate design of vent line systems is an involved process as the pressure loss imposed by the vent line piping can actually change the relief valve capacity, so that too is food for thought!

Oregon Jim
29-03-2008, 05:49 PM
As I understand it the regulation says we SHALL replace relief valves every five years and we SHALL test them annually. It is certainly an inconvenience and a big expense to change them every five years, but I am VERY HAPPY with the rule and comply without question or hesitation for many reasons.

First and foremost, it is for safety. There is no more important reason, but for me personally, it provides me with the excuse to empty my pressure vessels on a regular basis so that I may clean and inspect parts of the system that are inaccessable when the system is in operation. I can check for rust and corrosion in piping, clean and paint, repair insulation, and rebuild pumps and valves.

As we all know, a vast majority of management types look at the cost of maintenance and panic. They penny-pinch and cut corners, putting off maintenance and repiar until it cannot wait. This creates dangers that are unacceptable to me. I like the rule that says it SHALL BE DONE, as it removes the penny-pinching from the equation and it makes everone safer and more efficient.