hydrostatic testing of water pipes 1

[bansi]

Normally hydrostatic testing for chilled water/heating hot water distribution system is specified, to be tested at 1.5 times of working pressure. Is pneumatic test pressure (150 psig) in lieu of hydrostatic test acceptable? Which code governs for testing of chilled/hot water piping?

 

[mohtogh]

I think better place for this question is"piping &fluid mechanics engineering".This forum also has some active "responder"

 

[MJCronin]

bansi,

The place to find answers to your question is the piping code that the system is to be designed to (typically ASME B31.3 or B31.1)

Both codes allow pneumatic testing of systems, but only allow this type of testing when hydrostatic testing is "not practical" ( read: filling with or water residue would cause problems)

Typically, this type of test is reserved for low pressure designed systems (up to about 75 psig) or for large diameter, thin walled systems, where additional bracing and support would be required for hydrostatic testing

You should be aware of the dangers of this type of testing..... they are described in several of the piping related websites.

Hope that this helps


MJC

 

[skhungar]

Other responders have correctly pointed to the codes and more active links.
I would like to add two cautions:
1) Typically, the codes require pneumatic testing at higher pressures than hydraulic testing, e.g., 150% of maximum working pressure for hydraulic testing, but 200% for pneumatic testing
2) Be careful with certain materials. I have seen catlogs from PVC pipe manufacturers that warn that no pneumatic testing should be done.

 

[SooCS]

skhungar,

are u sure for pneumatic test is 2.0 X design pressure not 1.1 time.

 

[davefitz]

Whoa !!!

Pneumatic testing definitely must NOT be 200% of design pressure!! Read the code, and get someone familiar with the technology first.

When you hydrotest ( 1.5* design pressure in some codes, 1.3 times in other codes) , the worst eventuality if athe vessel fails is collapse of the vessel , but during a pnuematic test, the failure of the vessel is a catastrophic explosion. For that reason, all such testing must be above 70 F fluid and vessel temp and warmer than the documented ductile brittle transition temperature, and the pnuematic test pressure is usually to a max of 1.1 to 1.2 times design pressure.

Better recall the prior message before someone gets hurt.