NDT performed after or before Hydrotest test

[mrmalcolm]

Dear colleagues,
Any code mentioned Non-destructive testing should be performed after or before the hydrostatic test?
If non-destructive testing is performed after the hydrostatic test, is it possible that the hydrostatic test could cause minor imperfection to expand into major defects?
If non-destructive testing is performed before the hydrostatic test, could the pressure of the hydrostatic test cause the pressure vessel to explode?
Thank you.

 

[mfgenggear]

“To in sure weld integrity”. : INCORRECT
Pressure test is to check a pressure vessel integrity, not only the welds
Hydrostatic pressure test for piping is different for pressure vessels.

I think you lost it, better take a chill pill

 

[mfgenggear]

“To in sure weld integrity”. : INCORRECT
Pressure test is to check a pressure vessel integrity, not only the welds
Hydrostatic pressure test for piping is different for pressure vessels.

Nitrogen leak test

 

[mfgenggear]

After Cleaning fittingtack welding and welding atlas centaur oxygen and hydrozine fuel lines, a pressure test is conducted with helium. The welds do leak but it is very very light. Which then has to be repaired or reworked.

 

[r6155]

mfgenggear​

Increasingly confused.

 

[mfgenggear]

mfgenggear​

Increasingly confused.

What ever you need to work on your people skills.

 

[Christine74]

I have seen clients specify that RT, PT, and/or WFMT examination of welds be performed AFTER hydrotest for certain applications. Implicit in this requirement is the assumption that hydrotesting could potentially damage welds but I've only ever heard of this happening with austenitic stainless steel vessels that were hydrotested using water relatively high in chlorides.


-Christine

 

[mfgenggear]

I have seen clients specify that RT, PT, and/or WFMT examination of welds be performed AFTER hydrotest for certain applications. Implicit in this requirement is the assumption that hydrotesting could potentially damage welds but I've only ever heard of this happening with austenitic stainless steel vessels that were hydrotested using water relatively high in chlorides.


-Christine

Our shop had di water. Some of tubing and pipes
Did not allow city water. To many contaminants.

 

[DekDee]

What ever you need to work on your people skills.

I have blocked him - the forum is much more enjoyable for me now.

 

[DekDee]

I have seen clients specify that RT, PT, and/or WFMT examination of welds be performed AFTER hydrotest for certain applications. Implicit in this requirement is the assumption that hydrotesting could potentially damage welds but I've only ever heard of this happening with austenitic stainless steel vessels that were hydrotested using water relatively high in chlorides.


-Christine

Hi Christine,
Another Client without a clue.
I had similar requirements on my last project with specifications that were about 30 years old from a major US O&G company.
Did not take long to get the requirements waived with a bit of information provided.
Just out of personal interest - how would damage caused by high chlorides be identified by RT ?

 

[mfgenggear]

Hi Christine,
Another Client without a clue.
I had similar requirements on my last project with specifications that were about 30 years old from a major US O&G company.
Did not take long to get the requirements waived with a bit of information provided.
Just out of personal interest - how would damage caused by high chlorides be identified by RT ?

The products I was envolved with were for petroleum, chemicals, aerospace.
For many more. Applications varied.
Some of the products haver close tolerance diameters. Some of the materials inconclusive 718, inconclusive 625, titanium, hasteloy, waspaloy, 304, and 316 stainless. The process was unique. Plate sheared, brake formed, swaged, and pulled thru a sizing die.
No catamination was allowed with tap water.
Even the. Shipping paper had to be neutral.
Seam welds where automatic plasma, tig, .
Criteria was for the welds was very critical.
Ut, rt, penetrant. Visual , not in that order.
It depends if chloride contamination was an issue. Rt was not for the parent material.

 

[r6155]

If NDE is performed after the pressure test and a defect is detected and repaired , a new NDE must be made on the repair and pressure test must be performed again.
Obviously NDE must be performed before the pressure test to protect personnel.
Visual examination must be made before, during and after pressure test.

 

[Christine74]

DekDee I have no idea what the reason is for requiring RT after PWHT, but I found examples of this requirement:


"Nondestructive testing shall be performed, for the main part, during the normal fabrication sequence; exceptions (a) materials shall be tested in their final heat treated condition, and (b) pressure welds shall be radiographed after hydrostatic test."

"Magnetic particle inspection of weld O.D. surfaces after hydrostatic test is substituted for radiography."

"Liquid penetrant tests of weld preparations, back chipped surfaces and weld OD and ID surfaces. The weld ID shall be liquid penetrant tested after hydrostatic testing."

https://www.osti.gov/servlets/purl/4194007

-Christine

 

[r6155]

"DekDee I have no idea what the reason is for requiring RT after PWHT......."

Some pressure vessel requires RT (or UT) after PWHT because several defect can be produced by error during PWHT:
-ensuring uniform heating
-rate of heating / cooling velocity,
-supports inadequate in the furnace,
-control of temperature changes in the furnace.
etc.

 

[TGS4]

To (try to) directly answer the OP's original question of whether or not a pressure test can take an existing indication that may be an acceptable flaw and cause it to become a rejectable flaw:

The answer is yes.

However, that is taken into consideration when the original engineering work was performed to develop the reject/accept criteria. Once the vessel has successfully passed a pressure test, you are officially into the post-construction regime where indications are no longer accept/reject but subject to much more nuance. I've engineered existing pressure vessels to remain in service (cyclic service I might add) with substantial cracks left in-place and monitored. These crack-like flaws would be rejectable from an original construction perspective. It's all a FFS vs original construction mentality.

However, I strongly caution all to note that the presence of a rejectable flaw in a weld does not automatically mean that a vessel will fail catastrophically. Indeed, there are many vessels currently operating that had partial, spot, or none volumetric inspection. I ask you - what is the size of the indication/flaw in the weld that you did not inspect?

If you have a vessel in (very) severe cyclic service, I might be tempted to require a surface examination of critical locations after the pressure test - but solely in the context of a post-construction (but pre-service) indication locating and sizing activity. I'd hate to get into a test - examine - repair - re-test - re-examine - re-repair loop. That sounds like a good way to go crazy.

 

[DekDee]

DekDee I have no idea what the reason is for requiring RT after PWHT, but I found examples of this requirement:


"Nondestructive testing shall be performed, for the main part, during the normal fabrication sequence; exceptions (a) materials shall be tested in their final heat treated condition, and (b) pressure welds shall be radiographed after hydrostatic test."

"Magnetic particle inspection of weld O.D. surfaces after hydrostatic test is substituted for radiography."

"Liquid penetrant tests of weld preparations, back chipped surfaces and weld OD and ID surfaces. The weld ID shall be liquid penetrant tested after hydrostatic testing."

https://www.osti.gov/servlets/purl/4194007

-Christine

Maybe this was a little bit harsh. - Another Client without a clue.
As the Client is paying they can basically ask for anything they like that is additional to code requirements.
I just try to point out to the Client the actual code requirements may be totally different to a 30 year old project specification.
ASME VIII, B31.3 & B31.1

UG-99 STANDARD HYDROSTATIC TEST

(a) A hydrostatic test shall be conducted on all vessels

after

(2) all examinations have been performed, except

those required after the test.

345.1 Required Leak Test

Prior to initial operation, and after completion of the

examinations required by para. 341, each piping

system shall be tested to ensure tightness



137.1.5 Testing Schedule. Pressure testing shall be

performed following the completion of postweld heat

treatment required by para. 132, nondestructive examinations

required by Table 136.4.1-1, and all other fabrication,

assembly, and erection activities required to provide

the system or portions thereof subjected to the pressure

test with pressure-retaining capability.