Post Hydrotest Non-Destructive Examination

[PermanentCharpy]

I am manufacturing a set of pressure testing caps (blanks) which are threaded onto a length of pipe 3"IDX6"OD Pipe which is then hydro-tested to 22 500 psi. These parts are manufactured from AQ&T AISI 4130. During manufacture, volumetric and surface NDE are conducted after heat treatment and machining.

There are unfortunately no industry code & class requirements surrounding the above test pieces, but I would like to re-conduct surface NDE by wet fluorescent MPI after first use to ensure that any defects.

My concern is that the above approach is too conservative, but also does not serve a real purpose. In my opinion, it is unlikely that you would detect any cracking even if in fact the material failed / yielded during testing as the number of cycles from the first use is too small to detect crack growth if nothing was found in the initial inspection.

Is anyone in a position to offer advice on the above, either with reference to other code requirements for examination of equipment after load/hydrotest or first use, or a reasonable engineering opinion?

 

[TGS4]

What is the Code of Construction for your situation?

 

[MintJulep]

What is the expected stress in the cap under the hydrotest load compared to yield strength of the material?

 

[SnTMan]

What is the raw product form of the 4130? If plate, that's one thing, if forging, that's another.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[PermanentCharpy]

There is no specific code of construction - the equipment being tested is oilfield equipment manufactured under API 6A, but the testing equipment does not fall under anything - ie: my company and client have not instructed me to follow a specific code.

The expected stress is around 1/2 of Yield, with some high spots around maximum 2/3 of yield.

The raw is forged.

 

[EdStainless]

When we made test equipment for in house use it was given a proof test at some amount over the expected service, usually either 25% or 33% depending on the stresses. We then did wet fluor after that. We also had a re-test rule, again depending on service stress levels of every 10-25 cycles.
Caps and plugs had to be made from bar, no plate allowed. Clamps could be cut from plate, but there were rules about the orientation (L vs T) for the layouts.

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P.E. Metallurgy, consulting work welcomed

 

[jmec87]

Some API 6A equipment manufacturers make their hydrotest caps to the same requirements as the API 6A equipment. This generally works pretty well and I wouldn't expect any issues after a single test (just as I wouldn't expect the 6A equipment to have issues after hydro and it is normally not NDE inspected after hydro). If you are using it for many tests it is likely worth performing MPI eventually, but it is difficult to give guidance on how frequent this should be. It would depend on the design of your connection - if it is a robust design, it is likely fine for hundreds or thousands of tests before MPI, but MPI could be required sooner if it is a more marginal design.