NDT to piping that have been working over the MAWP determinated by ASME B31.3
NDT to piping that have been working over the MAWP determinated by ASME B31.3
(OP)
thread378-415848: Pressure Testing of Corroded Piping
Hi, i m studing a piping installation designed according ASME B31.3 code. For some reason the pressure riced beyond the desing and the PSV failed to open. [indent]The piping was working over the MAWP (+136%) for a while but without visual damages.
I need some std, code or general rules that determine the NDT or calculation necesaries in order to check the integruty of the piping.
I perform some calculation using the formula of ASME B31.3 to determine how far of the admisible tension the piping has been woriking.
The resulting working membrane tension (27.1 ksi) is grater (+37%) than the admisible tension for this pipe (20 ksi) but less than the yield strenght (35 ksi), asuming the worst esenario : the thikness reduccion due corrosion allowance and fabricaion undretolerence (12.5%).
For example:
Pipe 4" - Sch 40 - ASME SA106 -GrB
Working pressure: 995 psig
Temperarute: 90°F
Corrosion allowance: 0.125"
Resulting Tension: 27.1 ksi
Many thanks in advance,
Hi, i m studing a piping installation designed according ASME B31.3 code. For some reason the pressure riced beyond the desing and the PSV failed to open. [indent]The piping was working over the MAWP (+136%) for a while but without visual damages.
I need some std, code or general rules that determine the NDT or calculation necesaries in order to check the integruty of the piping.
I perform some calculation using the formula of ASME B31.3 to determine how far of the admisible tension the piping has been woriking.
The resulting working membrane tension (27.1 ksi) is grater (+37%) than the admisible tension for this pipe (20 ksi) but less than the yield strenght (35 ksi), asuming the worst esenario : the thikness reduccion due corrosion allowance and fabricaion undretolerence (12.5%).
For example:
Pipe 4" - Sch 40 - ASME SA106 -GrB
Working pressure: 995 psig
Temperarute: 90°F
Corrosion allowance: 0.125"
Resulting Tension: 27.1 ksi
Many thanks in advance,
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
Some practices might even treat this as simply a "pressure test during operation", possibly even providing a reason for uprating the MAWP. The pipeline rating procedure for pipelines not recently, or even never hydrorested, often have a provision for pressure rating by determining MAOP/MAWP based on the highest operating pressure experienced during the last year of operation.
Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
*** Per ISO-4126, the generic term
'Safety Valve' is used regardless of application or design ***
*** 'Pressure-relief Valve' is the equivalent ASME/API term ***
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
My star for you.
2) See Acoustic Emission Examination in ASME V to check integrity.
Regards
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
Huub
- You never get what you expect, you only get what you inspect.
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
Your numbers are wrong. You must calculate the stress with the actual thickness of the pipe.
Regards
RE: NDT to piping that have been working over the MAWP determinated by ASME B31.3
But at this sort of overpressure (i.e. less than the hydrotest), you simply need to do an engineering assessment and physical check of the system.
It almost certainly hasn't yielded anywhere so no real NDT to do.
But you need to find out how it happened, why it happened and what is being proposed to ensure that as far as possible it doesn't happen again. Like why did the control and safety systems allow this to happen? Procedures and operator awareness are not reliable enough to be used as the means to protect piping systems.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.