number of tie-in joints in a piping system

[siamak]

hi everybody
I work an inspector of construction project of a refinery plant.Due to wrong ETA(Estimated Time Arrival) of piping components; shortage of material in stock is going to make unacceptable delay in time schedule of construction plan, therefore managers are going to increase the number of tie-in joints up to 50 joints in a test package, and the contractor QC Manager believes that if one golden joint is acceptable by radiography test after installation of missed component with out hydro static test, then it is not rational to put any limit on this matter, now I request you to help me to find the reason of necessity of limiting the tie-in joint. I have considered the following reason:
- Tie-in joint is a concept of ASME B31.8 and it was considered as a factor in some design aspects and we use it in piping (designed based on ASME B31.3) for separating boundary of different subcontractor's in test packages.
If you are agree with the QC manager point of view, then why we hydro test piping or pipelines which their NDT percent is 100 ?(all joints were radio graphed.)
I will be so appreciated if you can help me with this question.
thanks for your consideration

[ardicool83]

Hi siamak.

To reduce the tie-in with golden joint, you can use flange connection, or you can parallel/joint the hydrotest if the same class (preesure test).
AFAIK Golden joint is accepted without hydrotest if NDT 100% for special case (tie-in).
You must to know that the fuction of hydrotest is not for test the welding quality, but for test piping material to handle the overall system.
In some case, hydrotest failed not happen in the welding, but in the pipe/fitting material.
Correct me if i wrong.

Thanks,
Hardi