Radiography vs hydro/pneumatic test 2

[ASHAGG]

One of our supplier for hot oil package piping system has requested for waiver of hydro / pneumatic testing as per para 345 of ASME B31.3? As per the manufacturer, hydrotest is not recommended because it may contaminate thermic fluid (one of the condition for waiver of hydro test mentioned in B31.3). Also they are reluctant to carry pneumatic test at approx 16 Bar (required test pressure) due to hazard asocited with pneumatic testing. They have carried our 100% Radiography for piping. I have generally waived hydrotesting for "Golden" welds but never for complete piping system. Also, I have been told that purpose of RT and hydrotest is different - RT is for checking integrity of welds whereas Hydrotest is strength test for piping. Would like to listen form experts

 

[metengr]

Hydrostatic testing serves a dual purpose; proof (design) test and check for leaks (missed defects) in welds and base material.

RT is a volumetric examination method but has limitations - namely orientation of flaws in welds.

Why not use the RT for welds and an in-service leak test using much lower pneumatic pressure to check for leaks?

 

[LittleInch]

Just get them to do the hydro using thermic oil or some other fluid which doesn't react with their thermic oil.

Quite right - hydrotest is essentially a system test - the test accurately tests the system including all weights, pipe reaction forces and also all pipes, fabricated and cast / forged components as well as the welds, which although important, are not the only pressure containing element.

Welds are probably the least likely item to fail in a hydrotest.

Also they could easily do a pneumatic test, but they just don't want to do it by establishing the right safety margins (concrete barriers, isolated location etc etc.)

Stick to your requirements and ask them to provide another fluid.

345.4.1 Test Fluid. The fluid shall be water unless
there is the possibility of damage due to freezing or to
adverse effects of water on the piping or the process
(see para. F345.4.1). [highlight #8AE234]In that case another suitable nontoxic
liquid may be used[/highlight]. If the liquid is flammable, its
flash point shall be at least 49°C (120°F), and consideration
shall be given to the test environment.

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