Air testing of utility pipes/water mains/sewer

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Permalink Reply by Troy Taylor on March 25, 2009 at 9:30am

While I do not have any in depth research I do have some experience with air testing pipe. In no way shape or form should you test plastic pipe with positive air pressure. See warning below:

WARNING: Compressed air or any pressurized gas used as a test medium may present severe hazards to personnel in the vicinity of the lines being tested. Extra personnel protection precautions should be observed when a gas under pressure is used as a test medium.
WARNING: Explosive Failure – Piping system rupture during pneumatic pressure testing may result in the explosive, uncontrolled movement of system piping, or components, or parts of the components. Keep personnel a safe distance away from the test section during testing.

At a power plant where I worked, repairing boiler tubes was a constant maintenance chore. Standard procedure after a repair was to hydro test the unit at full operating pressure of 1200psi, to find leaks. This took time to fill the boiler and ramp it up to pressure. If leaks were found the boiler would need to be drained again and the process repeated. To reduce the down time of the repair it was decided to use air pressure as the medium to find leaks. As the Safety Coordinator, I went on record as objecting to this un-best practice but management approved the procedure anyway. They did however set a limit of 7 psi on the test. I do not know how they arrived at that number. Although no incidents were recorded (we were lucky) during these tests and I could not prove air testing was effecting the passivation layer on the inside of the boiler tubes to stop the procedure, I was a nervous wreck each time the procedure was performed even though the tubes were heavy wall schedule 80, 316 stainless steel.

In my experience, testing with air is a potentialy hazardous short cut and should be avoided in any type of piping system regardless of material except for systems specifically designed for compressed gases. I do not think you will find any written procedures for air testing piping except for compressed gas systems because it is not safe to do so.

You can purchase a vacuum testing procedure from ASTM.org for certain kinds of piping materials. A safer practice.

I have attached a product bulletin from Harvel Plastics on the dangers of air testing plastic piping.

Attachments:

• air_testing[1].pdf, 248 KB

Permalink Reply by Chris Sears on March 25, 2009 at 9:53am

Thanks for the insight