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Posted By Ronofcam
Hey guys, need your collective wisdom again. I keep getting these ‘tricky to answer’ questions and though I’ve got the appropriate reading material (HSE Guidance Note GS4 (Third Edition)), it still doesn’t answer one very important point.
I am in the process of writing a risk assessment for pressure testing of metal pipework (copper, cast etc) post installation, and thought I’ve got most of it nailed, there are a couple of questions that I need answered.
Firstly, the testing process I am looking to implement is twofold: pneumatic and hydraulic. I intend to stipulate that the initial pneumatic “leak test” be carried out a specific pressure. However I can’t seem to nail what that pressure should be. I have heard the figure of 20mbar bandied around, but that seems excessively low to me. In order to get a good result I would have thought that a figure round about ½ - 1 bar sounds better. Although this was industry standard for a long time, I am no longer sure it still is.
Does anyone have a good answer to the above?
As for the second (hydraulic) test, I am going to stipulate a test pressure of 1½ times the operating pressure of the system (3 bar tested at 4½ bar etc). This is, apparently, the recognised figure for pressure testing (unless anyone knows differently).
Any answers/advice greatly received!
Regards,
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Posted By Bob Youel
The designers of the system should be able to give you this information as it should be a fundamental part pf the whole process
Please note this type of 'drop' testing can be very dangerous so do not undertake such work without adequate competent assistance
Additionally the components that are not part of the finished system must also be able to be pressurised and the physical mechanical fitting [setting iup the tests] on site should be of a high quality standard - I have seen 'black' bolts fail where they were used as temp fittings by inexperienced fitters
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Posted By Bob Youel
There are no generic industry test pressure recommendations that cover all areas!
Test parameters are obtained from many factors 'pressure' being only one of them! again go to the designer/s
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Posted By Exdeeps
Your insurers and or customer may have an opinion too, based on design requirement, service environment etc.
Jim
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Posted By Trevor Wilkinson
Ronofcam
Have a look at (hvca)TR/6.www.hvca.org.uk
Trev
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Posted By Jim Walker
Its a while since I was involved in this but so far as I recall you do not have to do both, just the more appropriate.
Hydraulic (by a considerable factor) is considered safer due to stored energy with compressible gas.
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Posted By Liesel
Yeah, talk to your insurer/inspector.... with steam locos we must do hydraulic test first, only once that is satisfactory will the boiler (insurance) inspector let us raise steam (pressure) in the thing.
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Posted By Ron Hunter
Most unusual to conduct both pneumatic and hydraulic.
Pneumatic OK for low pressure instrumentation (e.g. aircraft pressurised systems) usually using air/helium mix and sniffer probe - ensures integrity of brazing systems.
Hydraulic testing applicable to hydraulic systems is fairly safe where volume (and therefore stored energy) is small. If the system isn't leak tight you won't get pressure up anyway.
I seem to recall testing hydraulic systems of airborne radar scanners up to 2x working pressure, although some components were 4x ?
Long time since I was in that industry though. As others say, ask the Designer!!
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Posted By David McGuire
I have came across this problem with my previous employer. I don't think there is any set pressure. Would depend on what your pressure testing and what medium you are planning to use ie water or gas?
Would seek advise from a designer or your ICP! You will have to give serious thought to the design and location, and procedures that you are using?
I had a incident when a piece of equipment was being pressure tested in a designed test bay all procedures, PTW, barriers etc, were in place and adhered to, when the equipment parted in two and took of like a missile went through the test bay wall flew across the workshop and destroyed the archive store!
I will send you what I have on pressure testing.
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Posted By David McGuire
sorry send me your email and I will send you what I have
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