Penstock Hydrostatic Test

[sgarro]

For Penstocks: Can the hydrostatic test be susbstituted by 100% UT inspection on all welded joints?

Or the hydrostatic pressure test is mandatory?

thanks

 

[21121956]

Hello everybody:

sgarro, as a manner of general information for you, read these threads: thread404-277324
thread378-269828

 

[rconner]

You may wish to refer to MOP #79, "Steel Penstocks" of ASCE. [Beyond that, I would only say inspection of (welded etc.) joints only of course might not necessarily catch damage or mischief away from the inspected welds.]

 

[sgarro]

Hell rconner.

Actually I´ve looking for that document and I cannot find it anywhere, do you know where can I get it?

Thanks

 

[JStephen]

Maybe I'm missing something here- but if this is built to some design code, then it would be specified in that code- and if not, it would be at the discretion of the designers.

 

[rconner]

This ASCE MOP is reportedly "out of print" -- you might consider therefore contacting the Chair of the ASCE TAC Committee (charged with its revision) with your specific questions, or try to obtain a copy of existing hard-copy through a third-party source (e.g.

http://www.amazon.com/Penstocks-Manual-Reports-Engineering-Practice/dp/0872629511

or even E-bay etc.) or library.

 

[waterpipe]

What has been specified by the designer and the project documents? which standards are referred? if nothing is specified or you want to specify it at this stage then please consider:
The purpose of the hydrostatic field test is primarily to determine if the field joints are watertight. So the question is then: Can being watertight be checked by the UT?

In doing hyd. test, the test pressure should be maintained for at least 2 hours and there are permissible values for leakages. This makes me suspect that UT can be interpreted as a sign for being watertight.
Engineering monograph No.3, Weld Steel Penstocks by US department of the interior bureau of reclamation, states: "A proof hydrostatic test on the penstock after installation if most desirable. If the entire penstock cannot be tested hydrostically, individual sections may be tested in the shop after they have been radiographed. Hydrostatic tests should be performed .... to prove adequacy of all plates and welds with the required margin of safety."

I would say that a UT cannot assure the intentions of a hydrostatic test.

 

[sgarro]

Thank you all, I really appreciate your help. It's much clearer now.