HDPE Hydrostatic Pressure Test

[aicutler]

What is the most effective procedure for pressure testing thermal butt fusion buried HDPE. Our specs call for the section of pipe (approximately 370', 20")to be put under pressure for 24 hours prior to beginning test, to eliminate material stretching. Once test is started no leakage is allowed, but 1 gallon per 100' of expansion is allowed, even after the 24 hour preliminary pressurization is completed. I would like to find an alternate method.

 

[bimr]

http://www.ejprescott.com/docs/TestingProcedures.pdf

See page 59:

http://www.isco-pipe.com/pdf/designma.pdf

 

[rconner]

If I understand you correctly, after you conduct the long-term (24 hr) sort of pre-expansion period, you are now subsequently allowing (an additional) “1 gallon per 100' of expansion is allowed, even after the 24 hour preliminary pressurization is completed” for the actual acceptance test. I calculate of course 370’x (1 gal/100’) or 3.7 gallons of allowable make-up water for the short polyethylene pipeline.
I believe if you were alternatively testing e.g. 370’ of 18” ductile iron pipe (I suspect about roughly the same testing volume) per long-standing ANSI/AWWA C600 requirements, at lets say at 150 psi for a minimum required two hour test, I believe the maximum make-up water allowance for that comparable pipeline would be only about one gallon.
Since you are dealing with a relatively short buried pipeline, and with such a larger amount of water allowed to be pumped in for the hdpe, I guess I sort of understand your desire for an “alternate method” (after all with such a large amount of water pumped in to the buried line, and with all variables involved at that point, how can you be assured exactly how much of the make-up water is the pipe expanding and how much e.g. might be otherwise oozing out of imperfect, now buried fusions of joints, lateral connections, or installed flaws or damages to the pipe wall etc.? In other words, how are you really assured there is “no leakage” in the buried hdpe pipeline?)

 

[Zambo]

I haven't got the reference with me now, but will look for it. But in brief, you fill the line with water and then bring to the test pressure. The pressure should be held for about one hour, adding water as required to allow for expansion of the pipe. Then release the pressure to 90% of test pressure. Readings should then be taken for a period (can't remember how long). A graph should be plotted which should show an increase in pressure for a pass (i.e the contraction of the pipe increases the pressure) and a fall of pressure for a failure.

 

[stanier]

Suggest you download AS 2566.2 from SAIGLOBAL or find a WRc paper on the techniques used to test PE.