Duplex, super duplex stainless steel repair

[Ganesh Muthurajan]

Good morning sir, 

Now i working with duplex and super duplex , RO plant.

How to do the repairs in this material, for example we found two segment in 10 mm  in 14 inch pipe. 

Can we do partial repair, or fully cutout and reweld.  Any code reference advice to do full cutout, or partial.

Second case this plant was handed over to the Clint, during commissioning we found leakage, not only the butt joint, even in the branch connection, 

Aramco advise to do 100 %rt butt joint and branch.

Branch we can't do RT, placing a film is deficult.  What to do in this. 

Please advise me your experience and international, Aramco code reference.

Thank you

[Raghuram Bathula]

Dear Ganesh

what grade?, what type of failures (in NDE or in service?), any root cause analysis done.

Knowing the root cause and extent of damage is very important before attending repairs.

if you are considering these are as closure joints, then only Volumetric examination is permitted, otherwise check feasibility for in service testing

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[Ganesh Muthurajan]

Hi Mr. Ragu

The material grade is S32750.

And we found leakage in service, 

We will have random RT 90% are rejected and moreover PMI confirm the material in duplex not super duplex. 

after the root cause analysis we found corrosion on weld. Not in pipe and fittings.

The WPS used in production having more heat input compare then root pass. 

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[Pradip Goswami]

Hi S32750 is a super duplex grade. Repair welding is always more tricky than original welding. Irrespective of the issues, as 90% of the weld contains defects causing rejection, it would be advisable to remove the previous weld by machining and reweld with matching filler. As the base metal is S32750 (according to description) ER-2594 filler should be used. Welding heat input & welding parameters control should be exactly same as the Procedure Qualification.

DSS/SDSS are always used in extremely corrosive environments, hence due control of welding parameters and following the rules of fabricating DSS/SDSS would be advisable.

Aramco has extensive guidelines on welding DSS/SDSS. You may follow those or ask for that information as needed.

RT is difficult to perform on branch welds.However may be possible for larger dia welds.

Thanks. 

P.Goswami, P.Eng, IWE.

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[Mohd Siraj]

I will do two additional things,

1. check pickling and passivation are done properly after fabrication.

2. hydrotesting water is potable water and is clean with very clean air/dry air after the test.

The welding engineer is giving 300% attention during the fabrication which is true..but leave welding after welding and post-welding precaution is not taking place.

[Muhammad Azeem]

It's normal with this material experience happening in Aramco different site .

You need to conduct 100% RT for but joint and conduct PT for branch connection.additionaly UT can be done .

For repair you need to conduct repair only for this as per requirement in SAES -W-16 separate repair WPS required .that repair procedure should be done full thickness repair..

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[Student]

Ganesh

 Super duplex welding should be planned carefully. Do not exceed 1.5kj/mm heat input. High heat input leads to the formation of intermetallic phases in SDSS. For that reason, repair welding is not usually recommended. Also, use purge gas with 2% Nitrogen. Nitrogen is responsible to provide pitting corrosion resistance. During welding, some of the nitrogen in the base metal will be lost. To make up usually 2% Nitrogen is added. 

Is this in Jizan RO plant. 

On Thursday, December 8, 2022 at 10:52:39 AM UTC+3 GANESH MUTHURAJAN wrote: