JABoomer
Mechanical
- Jan 9, 2014
- 20
Hi All,
Can across a situation yesterday and I am still unclear on the details.
Had a 150# piping system with a design pressure of 1770 kPA. Now that would make the minimum hydrotest pressure 2655 kPa. The Client actually had the hydrotest pressure set at 2948 kPa which I was fine with. However they later requested the hydrotest pressure be increased to the ANSI maximum allowable non-shock pressure for a 150# flange rating of 3105 kPa (450 psi), as per the following table:
Their reasons for the change is they like to make the hydrotest the maximum allowable in case the design pressure is change down the road, that way they don't have to re-test the pipe if the design pressure is increased.
I see several problems with this: The inspector will always want to see the test pressure during the hydrotest indicating equal to or above the stated hydrotest pressure, which means there is a danger of exceeding the maximum allowable non-shock pressure during the test. Also, if you were testing a vessel, or even a large vertical run of pipe, the additional hystrostatic pressure from the water used during the hydrotest could further exceed the maximum allowable pressure.
I think you are allowed to exceed your hydrotest pressure by 15%?
But can you exceed the maximum allowable non-shock pressure AT ALL? And if you do do you have to perform stress calculations to ensure the pipe has not been over-stressed?
Can anyone help me out on this one. Is it okay to have your hydrotest at the maximum allowable non-shock pressure as indicated by ANSI?
Thanks Much,
JABoomer
Can across a situation yesterday and I am still unclear on the details.
Had a 150# piping system with a design pressure of 1770 kPA. Now that would make the minimum hydrotest pressure 2655 kPa. The Client actually had the hydrotest pressure set at 2948 kPa which I was fine with. However they later requested the hydrotest pressure be increased to the ANSI maximum allowable non-shock pressure for a 150# flange rating of 3105 kPa (450 psi), as per the following table:
Their reasons for the change is they like to make the hydrotest the maximum allowable in case the design pressure is change down the road, that way they don't have to re-test the pipe if the design pressure is increased.
I see several problems with this: The inspector will always want to see the test pressure during the hydrotest indicating equal to or above the stated hydrotest pressure, which means there is a danger of exceeding the maximum allowable non-shock pressure during the test. Also, if you were testing a vessel, or even a large vertical run of pipe, the additional hystrostatic pressure from the water used during the hydrotest could further exceed the maximum allowable pressure.
I think you are allowed to exceed your hydrotest pressure by 15%?
But can you exceed the maximum allowable non-shock pressure AT ALL? And if you do do you have to perform stress calculations to ensure the pipe has not been over-stressed?
Can anyone help me out on this one. Is it okay to have your hydrotest at the maximum allowable non-shock pressure as indicated by ANSI?
Thanks Much,
JABoomer