RT for piping

[waliq]

Hi all,

We have a diesel storage tank whose diesel lines are of NPS4", NPS3", NPS2" and NPS1.5"

The operating pressure in lines is 3.5 Bar at pump discharge and operating temperature varies from 40-60 Deg C. The line material is A53B standard schedule thickness

We used SMAW welding technique to weld these lines.

PS: We do not have design company's Piping material specs, nor was the WPS available. We needed to weld these lines in a short duration.

After welding, we did its PAUT. However, the scan shows presence of slag. However, no crack is reported. We did its DPT afterwards, which was clear.

I have the following questions

1) Is it fine to employ SMAW welding technique on these diesel supply and return lines?
2) Is it required to employ GTAW technique on these lines?
3) What is the requirement of UT or RT on these lines?

 

[Krausen]

1) Yes, SMAW is fine for carbon steel piping (A53B pipe)
2) No
3) UT & RT are both forms of volumetric NDE inspection. If you performed PAUT to the minimum number of welds required by the piping code you're following, then you typically would not need to perform RT on top of that. Typically at this size of piping, RT would be performed.

I would still confirm that whatever WPS was used matches up with the company's WPS though.

 

[waliq]

@Krausen: Thanks for the response!

The inspection Manager at my company has the view to employ GTAW technique for atleast the root pass followed by SMAW for remaining (Hot, intermediate and filler) passes.

1) However, I need to know any ASME (B31.3 or Section IX) clauses to negate this opinion as we have used SMAW for root, hot, intermediate and filler passes

 

[1503-44]

Seems like overkill to me.
What are his reasons for doing it?

GTAW Advantages and Disadvantages

https://www.thefabricator.com/thewelder/article/arcwelding/the-whats-whys-and-whens-of-gtaw

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[weldstan]

Under B31.3, 5% RT is required and each welder shall have at least one weld examined.

 

[Krausen]

@waliq: GTAW for root buttweld passes on pipe is a common requirement in many applications in order to eliminate any weld slag on the ID of the final pipe weld. This is never a bad idea, but you many be able to challenge the need for this in this case. If it's just clean diesel service, this shouldn't be a mandatory thing. Especially if you've passed all your NDE inspection already & the final welds checked out. The codes (B31.3 or Section IX) won't provide a clear "yes/no" on this specific requirement from your Inspection Manager, as they leave items like this open to the Owner/End User to determine.

 

[mk3223]

PS: We do not have design company's Piping material specs, nor was the WPS available. We needed to weld these lines in a short duration. [/quote ]
Is the welding for the piping a temporary work since the work was in a hurry and may not be complied with the design company spec?
The questions are what's the hurry for the work without planning? And, is the pipe welding procedure and result acceptable by he Client?

 

[weldstan]

Do you have a qualified WPS and are welders also qualified? Under B31.3, they must be. if you are the contractor, you should/must have the above.

 

[Dhurjati Sen]

Your Inspection Manager has got his way by now, hopefully.

Because he was right.

Piping 2" and below ought to be fully GTAW, especially in oil and gas industry, where it is a standard practice.

DHURJATI SEN
Kolkata, India

 

[DekDee]

Agree with all comments above.
SMAW is used for root runs daily on pipelines but they then have cleaning pigs sent down which removes the slag.
Celluose slag comes off much easier than low hydrogen slag.
Even with GTAW root runs we insist on a Flushing and Drying procedure to ensure internal cleanliness of piping.
Have you performed flushing and drying ?

 

[r6155]

Some slags are allowed. See limits in B31.3

Regards