Hydro Test and Pipeline Design

[LeitoGM]

Good Day Everyone,

2 simple questions:

- What determines the hydro test pressure of a spool section? I keep ready 1.5 time the design pressure, could someone elaborate on that?
- If there is a TOL fillet welded on the middle of the pipe, how would you carry on a hydro test?

Thank you

 

[swsweld]

The test pressure isn't always 1.5 of design pressure or MAOP. Different codes have different test criteria. Some Classes in B31.8 are only 1.1, 1.25 or 1.4 of design pressure.

B31.3 states in 345.4.2
PT=1.5 PRr
where
P p internal design gage pressure
PT p minimum test gage pressure
Rr p ratio of ST/S for pipe or components without
established ratings, but shall not exceed 6.5
p ratio of the component pressure rating at the
test temperature to the component pressure
rating at the component design temperature
for components with established ratings, but
shall not exceed 6.5
S p allowable stress value at component design
temperature (see Table A-1)
ST p allowable stress value at test temperature

All materials, components, joint and weld design should be capable to handle the internal and external stress and test pressure.

Is the TOL fillet welded only, or is it fully penetrated groove weld with a fillet reinforcement as shown on B31.3 Fig. 328.4D?

 

[LittleInch]

What determines the test pressure - the pressure in the design code as swsweld says. For steel piping this is very commonly B31.3, so the test pressure in that code is 1.5 time design pressure.

Is TOL a threadolet? You just need your final pipe threaded into it or a plug if it's not connected and hydrotest the spool. What you're testing is the weld between the fitting and the pipe, not the seal on the threaded component.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[jte]

If there is a TOL fillet welded on the middle of the pipe, how would you carry on a hydro test?

Use a thread-o-plug. Unless the threadolet was (groove with fillet) welded to the pipe but a hole was not cut in the pipe.