ASME B31.3 Leak Testing Piping (Static Head)

[cmontminy]

Here is a question about B31.3 Hydrostatic Test.

LDT Test Pressure is 450 psi
DP: 275 psi
CL 150# rated fittings
Test relief valve set at

During the leak test, the low point gauge was reading 450 psi as per LDT required test pressure. High point gauge (about 80-100ft up) was reading 400 psi. As the inspector I judge the test insatifactory as per B31.3 par 345.4.2 which says ", the hydrostatic test pressure at every point in a metallic piping system shall be as follows (a) not less than 1.5 times the design pressure."

Fabricator judges the test satisfactory as he refers to the client spec which apparently says to use gauge at grade.

Client Spec states: The preferred location for pressure test gauge shall be at grade near the pressure test pump. Readings may be made at higher points providing the gauge pressure reading plus the static head between grade and the point of measurement does not exceed the maximum test pressure

From experience, the test pressure reading is always taken at the high point gauge. Therefore the high point gauge should be reading 450 psi and the low point gauge would be 450 psi plus static head pressure. Client spec to me is not clear at all. If reading is taken at the higher point : reading + static head = max test pressure. What I do not undertsand is that the high point gauge would not have static head. Anyone interpret the spec differently?

The reading of pressure during a leak test is done at the high point gauge or the low point gauge?

 

[DSB123]

if you have not pressurised the pipework at the top to the test pressure then it is not Code compliant. Nothing else to be said.

 

[DekDee]

Agree with DSB123 100%.
A clients specification may install stricter guidelines than the code but it cannot state requirements lesser than the code requirements.
If you do not have a minimum of 450 psi "at every point" then the hydrostatic test does not comply.
Regards,
DD

 

[cmontminy]

This is what I believe as well. However they say they will not reach 450 psi at high gauge because they will exceed the flange rating pf A105 Class 150 flange. I do agree they should not exceed the 450 psi. My point is that in this case they should test the length on pipe in 2 or more sections so that the 1.5xD.P (275 psi x 1.5 = 412.5 psi) is reached and avoid exceeding the yield strength of the flange rating by keeping the test below 450 psi at the bottom.

 

[DSB123]

cmontminy,
You are correct they need to split the pressure test and test each section to the required test pressure to be Code compliant.