Hydrostatic Testing, Radiography Test for pipes

Please confirm a couple of things:

• Which fluid service is your system designated (most likely Normal)? But just in case - Normal Fluid Service, Category M, or Severe Cyclic (it will not be category D because it is flammable).
• The entire piping system contains 18 welds total, and every weld was examined.
• The welds that "failed" actually do not meet the requirements of Table 341.3.2, and that by "fail" you are not just stating that defects were found.
• Can you list the defects/sizes/locations that were found?

Because, depending on these answers take this scenario for instance.

If your system has been designated Normal Fluid Service (with 5% random RT on butt welds) you may be perfectly fine. It is not the intent of ASME B31.3 that the examinatino ensure that the constructed piping system will be free of defects, even ones that are rejectable if found. Nor is it required that welds that are not examined be free of rejectable defects. Instead, the examination work is part of an overall quality assurance procedure. The leak test is used to test the overall system.

Interpretation 5-18 (May 5, 1987) addresses this point:

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"Question (2): Assuming the Engineering Design requires fabrication to ANSI/ASME B31.3, requiring the minimum 5% visual examination and random radiography of girth butt welds, what is the minimum weld quality required by the Code for butt welds which have not been individually examined, but were represented by a successful random visual and radiographic examination?"

"Reply (2): The Code accepts such welds subject to leak testing. Note: The Code assumes that the 5% which were required to be examined will be representative of the entire lot, by a guarantee of such is a contractual matter to be specified by the engineering desig./"

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If a piping system passes the examination requirements of the Code, it is accepted (complies with the Code) if it passes the leak test. If additional examinations are performed that reveal defects, it is beyond the Code requirements; the system already complied with the Code, and the issues of whether ot repair those defects and who is to pay for the repair is a purely contractual matter. The defect can be left in and the piping system will still comply with the Code. Of course, it would be judicious to at least perform a fitness-for-service evaluation of the defect if it is intended to be left unrepaired.

As per 31.3 code hydrostatic shall be conducted 1.5 time the design pressure, regarding RT 5% girth is mandatory requirement , however RT percentage always decide by client speciation or based on joint efficiency factor by designer . IF any joint fail in RT , As per B31.3 there is two penalty RT for each repair per welder.

Mkhan

For pipeline you have to pass the code requirements and the high percentage of failure is strictly not acceptable.

More so since you are working with inflammable liquid.

The hydro test will pass in any weld joint quite easily since a small plug on the defect say a pin hole will not allow the fluid to pass through.

However when the line goes in actual operations, there is a possibility of the defects extending till the pipe fails.

This extension of defects may be due to

corrosion

Cyclic stresses (fatigue)

Normal operating Stresses

Stresses created due to supports, bends, overhangs etc and these will not be accounted for when you are working with hydrostatic test.

Both Hydro and RT/UT etc are complementary and in our pipelines where these are handled (Gas Pipes etc) - additional LPI/MPI depending upon the fluid is carried out. Of course these being for customers, we go beyond the statutory codes.

Moral of the story: forbidden even if urgent, repair. One can not play with safety of persionnel/ plant.

Woof!!! The X-Rays don't lie! I hope your pipeline runs no where near people. You don't want to be like the people in Southern California that suddenly heard it raining, but on closer inspection found out that their entire neighborhood was being showered in gasoline from a busted pipe!!!