I need your expertise experience

[Rasheed Khan]

I need your expertise experience to clarify or prefer the below situation.

One new line to be directly connected to an existing line with tee, the existing line will
be cut and install new tee and then the new line will be connected or tie-in to the existing line, now the next activity is to conduct the
hydro test for new line and tie-in points and found two arguments or approach which is explained in below in two scenario.

Scenario -1
A temporary blind flange to be installed on new line and test the system in accordance with ASME B31.3 After Tie-in with existing line, shall be tested again according the pressure
calculation based on remaining thickness of the existing Piping. But in this case whole system (including existing and new ) will be tested twice.

Scenario -2
The system shall be tested once completion of the tie-in or connected
to the existing line with the pressure calculated or limited based on
remaining thickness of the existing Piping. So in this case the system
the whole system (including existing and new ) will be tested one time..

 

[LittleInch]

You can do either.

The issue is that the lower of the two tests will set the MAWP of the system.

Therefore unless you plan to repair / replace the corroded line later on, I would go for test 2.

The issue then is a paper one whereby the pipe specification / line list will need to be modified to show that your new line was actually only tested to the (presumably) lower test pressure of the corroded line.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[metengr]

Why would the existing line need to be subjected to a hydrostatic test? Makes no sense. The new line should be hydrostatically tested per B31.3 code, installed to the existing line, and conduct an in-service leak test to ensure the connection weld is sound.