hydrostatic testing of pipelines 2

[staffman]

I am in the process of pressure testing an HDPE pipeline that currently contains water and i'm sure a certain amount of air. Is it imperative that I expel the air first? and why. How will it effect my test if air is left in the line. Thank you

 

[CESSNA1]

STAFFMAN: It is usual to remove all the air when hydrotesting. The air can compress and if the pipe fails there will be an explosion and shrapnel all over. If the test medium is water, everyone just gets wet. It goes without saying to keep all people a safe distance away from the test article.

Regards
Dave

 

[JStephen]

Perhaps a non-issue...but on typical rubber-jointed pipe, you have a leakage allowance. I assume the volumetric leakage rate would be a lot higher if you were leaking air than if you were leaking water.

 

[stanier]

There are specific testing protocols for HDPE pipelines that are different to ferrous pipelines. Download a copy of AS 2566.2 from Standards Australia or find similar treatise in WRC or AWWA websites. You may want to investigate the Driscopipe website as they may have the test procedure there.

The main difference is that the HDPE suffers from creep during the application of the test pressure. This is compromised by air in the syste. The test procedure is aimed at ensuring that you measure a pressure rate to reflect the creep and that all the air has been expelled.

 

[rconner]

I think there was a discussion on testing of such pipe also at

http://www.eng-tips.com/viewthread.cfm?qid=133832&page=2.