Hydrostatic pressure Test for pipes

[DiplingAndre]

Hi Everyone,
I have a question. Is there anywhere a clear definitaion what a hydrostatic pressure test is? I mean the pressure test of a single pipe (by the manufacturer) not a complete system.
Is the test a leak test, where you pressurize to the test pressure, stop pumping and see if the pipe is tight and the pressure does not decrease?

Or is it a kind of stress test, by means you pressurize the pipe to the test pressure and hold it there? Decreasing pressure (due to small leackages in the system) can be balanced by pumping during holding time. And the acceptance criteria is that the pipe does not deform, leaks or bursts.

 

[redpicker]

You really need to look at the specification that is requiring the hydrostatic test as it will give the specific requirements for the test. Some manufacturing tests are intended to verify the pipe can withstand the test presure without bursting, while others are used to verify the sealing capacity of the connections. There may be other reasons to hydrotest as well.

In general, however, if you are pumping, you are not holding, so pumping during holding time is not permitted.

rp

 

[metengr]

Leak test and hydrotest are not the same test. A hydrotest is normally specified by a Code of construction and requires pressurizing the item with water to a specific design pressure and holding pressure for a prescribed period of time to check for pressure loss caused by visible leaks. A hydrotest is also used to validate design under internal pressure, where the item is checked under hydrostatic pressure for deformation.

A leak test is similar to a hydrotest except the pressure is defined by either a standard or specification and is based on a pressure to detect only leaks. The leak test is commonly used to check for leaks at flanged joints and connections, and is not necessary to proof test an item.

 

[stanweld]

Refer to 20.1 of SA-530 and 22.2 of SA-999. These provide the requirements for the hydrostatic tests of the various pipe specifications referenced therein.

 

[DiplingAndre]

Thanks for the quick response guys.
Yes I was checking the ASTM A 999 but its still not very clear. If it would be a "kind of leak test" where you survey the pressure lost you could pressurize the pipe alwayys with the same pressure (for example 10 bar). But you need to calculate the test pressure to produce a defined stress so it looks to me like a "stress test". If it is a kind of stress test the main thing is that the pipe can withstand the pressure and it should be no problem if you pump during holding time or a small loss of pressure as long as the minimum pressure and therefore the stress is applied.
Is it correct?

 

[stanweld]

Whereas the hydrostatic test pressure defined in A-999 is 60% of the SMYS for ferritic steels and 50% of the SMYS for austenitic stainless steels, the test is a leak test and it can be lower per 22.2.2. This is a fast test (minimum hold time 5 sec.) performed by the pipe manufacturer to discover defective pipes. It is considered a Nondestructive Test as defined in Section 22; however, it can be quite destructive for some pipes tested.