Hydrotesting with glycol
Hydrotesting with glycol
(OP)
Need some advice about hydro testing in cold weather with glycol.
-Understand when pipe temp rises the pressure goes up.
-When pipe temp is dropping the pressure will drop.
-How much would you compensate for pressure drop?
-If glycol in the storage tank & the pipe temp are within 2-3 degree difference.
Should the pressure drop be minimum like a 1 to 5 pound drop.
When I walk the line for leaks find no traces of a leak (only within the test limits)
The PTR & specs for Company X say to Hold test for 10 minutes
Look on internet not much help.
Would you know if there is some type of chart for pressure lost at minus temperatures





RE: Hydrotesting with glycol
Fluid expansion, pressure increases with temperature increase, for most fluids, but some (yes water is one) depend on the temperature and the temperature range during the test. The resulting pressure varies with temperature depending on the temperature expansion coefficients of one in relation to the other.
For a 10 minute test, I doubt that temperature will stabilize enough to get much of a test, or really be a factor worth considering, as there shouldn't be much temperature change in 10 minutes, other than to determine if there is tightness or not. That would hardly be enough time for the pipe temperature and fluid temperature to equalize.
Therefore, if its just a short time tightness test, I wouldn't worry much about temperature at all. If you get any effect, what you're measuring would not give an accurate indication of leaks anyway.
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"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Hydrotesting with glycol
I don't know what the coefficient of thermal expansion of glycol is, but with water it works out to about 100 psi pressure change (from elevated pressure) for every degree F of temp change, so your 2-3 F temp change could be 200-300 psi pressure change. I'd find out what the number is for glycol before starting a glycol test.
In a 10 minute test, nothing will reach an equilibrium temp so your question doesn't feel right to me, it feels like there is something missing.
I've got a document under "samples" on my web page that might help you answer some of your questions.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
"Everyone is entitled to their own opinion, but not their own facts" Patrick Moynihan
RE: Hydrotesting with glycol
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"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Hydrotesting with glycol
50/50 glycol is a very leak-prone substance (NFPA 37 recommends welded over threaded fittings for it). If you can't see a leak and there's no where for it to leak internally (i.e. past a valve into a vessel) it's probably a temperature issue.
How much is your test pressure dropping?
RE: Hydrotesting with glycol
B
RE: Hydrotesting with glycol
RE: Hydrotesting with glycol
As I recall ASME I requires a min metal temp above 60 F for hydrotest, based on alloys weldments, and heat treatments permitted in that code.
Most of the catastrophic failures of presure vessels that I can recall during hydrotesting were related to failure to ensure adequate metal temperture to avoid brittle fracture.
RE: Hydrotesting with glycol
RE: Hydrotesting with glycol
Testing pipe.
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"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/