ASME B31.3 Extent of Required Examination 1

[CobusvanJ]

Hi,

I have a question regarding ASME B31.3 para 341.4.

The 8" Sch. 80 SA-312 TP316L piping will be in Normal Fluid Service (water at 50deg C and 70bar) and according to para 341.4.1(b)(1) 5% or more of circumferential butt welds shall be RT-ed or UT-ed. My question is regarding a 1" branch for instrumentation. What NDT is required by ASME B31.3 for this branch? It appears from the paragraph that NDT is not required for small bore branches.

From the same paragraph it states:"In-process examination in accordance with para. 344.7 may be substituted for all or part of the radiographic or ultrasonic examination on a weld-for-weld basis if specified in the engineering design or specifically authorized by the Inspector.". Does this mean no RT or UT needs to be done as long as the requirements of 344.7 is met?

I want to make doubly sure I understand correctly as I come from oil and gas where EVERYTHING was RT-ed or UT-ed, so I worry when it appears not to be required for a pressurised system...

 

[LittleInch]

I think so, yes but you need the "if..." bit to be valid.

Not all Oil and Gas systems are 100%, many are 5 or 10% in my experience.

the branch welds are just part of the whole so might be tested or might not.

B31.3 is a minimum requirement, normally this aspect is enlarged on in a customer specification. If you want more than the minimum then say so and pay the price.

You need to pressure test the whole thing to 1.5 x Design pressure in any event so that should be enough to pick up any serious flaws.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DekDee]

As LI has stated, additional NDT is usually noted in project specifications or contract documents

341.5 Supplementary Examination
Any of the methods of examination described in
para. 344 may be specified by the engineering design to
supplement the examination required by para. 341.4.
The extent of supplementary examination to be performed
and any acceptance criteria that differ from those
in para. 341.3.2 shall be specified in the engineering
design.

 

[XL83NL]

What NDT is required by ASME B31.3 for this branch? It appears from the paragraph that NDT is not required for small bore branches.

Well, VT is also considered NDT, and in my opinion, it can be far more effective than RT (when executed properly, it can waive out most defects before RT starts - and, VT finds defects which RT cant find). So NDT can be considered required for small bracnhes, as the scope B31.3 refers to is all-inclusive.
VT is always part of the NDT scope for B31.3, and certainly for welds:

(a) Visual Examination. At least the following shall be
examined in accordance with para. 344.2:
(1) sufficient materials and components, selected at
random, to satisfy the examiner that they conform to
specifications and are free from defects.
(2) at least 5% of fabrication. For welds, each welder’s
and welding operator’s work shall be represented.

 

[david339933]

You are going to need a solid argument to get an AI to accept in process examination for any other weld than the closure weld.

 

[KevinNZ]

We use B31.1 for piping and this code allows service leak test with just VT. This frustrates the inspections who are expecting 10% RT and hydro tests. Clients who know what they want add extra inspection and testing to the contract specifications.

Note 10% NDT inspection misses 90% of the defects.

 

[LittleInch]

Most inspection clauses increase the level of inspection if defects are found or a particular welder is exhibiting poor welding.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

Note 10% NDT inspection misses 90% of the defects.

What makes you think that?

 

[KevinNZ]

Food for thought. Without extra tests on additional welds after a defect is found, the other 90% of the welds not NDTed could have undetected defects. The 10% tested could be clear and the other 90% all have defects, In which case you have missed 100% of the defects.

I try get the most value from the 10% NDT by using this to test the first welds of each welder on the job and testing more welds if they have problems. Too many fails and they are off the job. Lets the welders know you are serous and they get keep up the welding quality from the start.

The level of NDT is considered by the safety factors in the design code.

 

[david339933]

I'm sure your welders are aware of your testing as well.....one good weld at the start and they can slap together the rest. Usually the intent is random radiography as well....doesn't sound very random.

 

[KevinNZ]

We still have random test as well as the tests at start of the job.

Agree with you about welders knowing if tests will be carried and changing behaviour. A welder said to me after a failed test, "why didn't tell me you were going to test it"

 

[GD2]

CobusvanJ,
Most likely you are using a MSS-SP-97 8" x 1" XS branch fitting to weld to the NPS8 80 sch pipe. Now the weld on the run pipe with this fitting is always a butt weld regardless of the outlet connection, that can be butt weld, socket weld or threaded. The outlet connection will most likely be a socket weld for the service condition stated (usually they keep SW upto 1-1/2" size for ease of welding for small bore pipes).
If that is the case, both the butt-weld and the SW can be RTed.
ASME B31.3 don't specify which weld to NDT and which not. It is usually, the AI who will do that job.
In-process examination is allowed by the AI under specific circumstances.




Ganga D. Deka, P. Eng
Canada

 

[curtis2004]

KevinNZ (Mechanical)13 Feb 18 19:56
We use B31.1 for piping and this code allows service leak test with just VT. This frustrates the inspections who are expecting 10% RT and hydro tests. Clients who know what they want add extra inspection and testing to the contract specifications.

Note 10% NDT inspection misses 90% of the defects.


Kevin,

B31.1 is not only a different code than B31.3, but also has a different requirements for radiographic examination and even a different acceptance criteria.

In B31.1 piping 100% RT required at higher temperatures and pressures. Simply adding 5% or 10% RT for low temperature and low pressure B31.1 piping without additional agreement on how to deal with "defective welds" (which didn't pass B31.1 acceptance criteria) and welders who made those welds may cause unintended consequences.

See below a link to an article about random radiography:

https://www.thefabricator.com/article/testingmeasuring/random-radiography

 

[GD2]

For info, B31.3 allows service tests on Category D Fluids, the simplest of all fluids. Examples are utility water and air lines in a plant where there is no risk if we find few leaks during the test.

Ganga D. Deka, P. Eng
Canada

 

[DekDee]

I agree with Curtis's comments.

If the client decides they want additional volumetric NDT (which is well within their right) for low pressure or low temperature applications do they provide a separate acceptance criteria ?
If not, the B31.1 acceptance criteria for volumetric NDT is based on high temp and/or high pressure so would not be applicable to low temp and/or low pressure.(could therefore make significant cost implications for somebody)

I also find it hard to understand this comment " This frustrates the inspections who are expecting 10% RT and hydro tests"
Who is it you are actually frustrating ?
Regards,
Shane