In situ Solution Annealing for SS321 piping connected Catofin Reactor 1

[Niladri79]

Dear all,

I have come across a typical requirement form one customer to include Solution Annealing activities of existing pipeline before cutting the same for any modification. The intended purpose is to prevent any crack from being propagated during cutting operation, as per customer. The metallurgy is SS321H, 30" NB, operating temperature is 600+ deg C, likely cyclic service. We need to take a tapping in the existing header and replace a portion of the 30" header. The line is part of the inlet line to the Catofin reactor in an MTBE plant.

I have already exhausted the limited resources, I had, but could not find any such requirement or reference for the same. My specific questions are:

1. Whether there is any requirement of Solution Annealing or any other heat treatment for existing pipeline, before doing any cutting operation.

2. IS it possible to carry out solution annealing at site on existing pipeline (on elevated structure)?

3. Does anyone have any experience of such an activity, or is there any reference material (codes/standards etc) where such requirements are mentioned?

Would really appreciate any fruitful response from members, before I go back to client to ask where are they coming from on this?

Thanks and best regards,
Niladri

 

[EdStainless]

Possible, maybe, but I have no idea why someone would want to do this.
If it were me I would first inspect for cracking (LP) and then do some hardness checks.
If there are cracks you would need a plan to cut well away from them, since those sections would need to be replaced anyway.
And if there are places with unusually high hardness you would also want to be working away from them.
Unless they expect this system to have huge residual stresses (which should be noticeable by distortion)I don't see why HT before cutting would be of any value.
I am not sure how you would anneal 30" SS that is in an elevated location, and not make things worse than they already are.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

I would never attempt solution annealing in place for this material. The disadvantages well out weigh the benefits.

 

[weldstan]

I've never seen this done in situ and never prior to cutting out a section to be replaced. There will always be two locations adjacent to the ends outside of the heat treatment zone that will be sensitized. Also the potential for damaging the line is extreme. I have seen stabilizing anneal treatments done in situ after welding to replace the cutout section.

 

[weldstan]

They may be asking for it to eliminate sigma phase at the new weld joint locations.

 

[pradipgoswami]

Niladri,
You may go through ,API TECHNICAL REPORT 942-A,Material, Fabrication and Repair Considerations for Austenitic Alloys Subject to Embrittlement and Cracking in High Temperature 565 - 760C (1050 – 1400F) Refinery Services for guidance.
SS 321H metallurgy, operating temperature regime is quite conducive for Sigma Phase formation. Also Carbide formation from original welding conditions are possible,though the alloy Ti stabilized, but it contains higher "C".
Solution anneal would remove the deleterious phase, but proper supports are required to prevent, buckling/distortion, which is difficult to ensure in site.
As an alternative may perform replications on single or multiple spots of the component to be replaced to get the first hand information & then proceed accordingly.
Thanks

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299