Boiler Tube welding

[Raai2015]

Dear All, This is for the Boiler final Superheater. FSH tube material is TP304H (please dont ask why as customer forced me use this as this is EFW Boiler). Header material is P22. I suggested Intermediate material of T91 otherwise i say they have welding issues. But customer wants to weld Austenite (TP304H) with Ferritic(P22). Can somebody through some insight and supporting codes if any??
Baskar

 

[weldstan]

Why would you prefer a T91 to 304H joint over aa 2 1/4 Cr-1Mo joint? The coefficient of expansion mismatch is greater with the T91/304H joint. I would suggest welding pigtails of matching tube to the header and welding the pigtails to the 304H tubes, which can be made without PWHT.

 

[Raai2015]

Hi Weldstan , would you please elaborate on this ''matching tube to the header and welding the pigtails to the 304H tubes, which can be made without PWHT.''

 

[EdStainless]

I believe that Stan is suggesting welding 304H pigtails to the header with 2 1/4Cr filler, then PWHT the header as required.
Then you can make the 304H to 304H welds with 304H filler and there is no PWHT needed for this weld.

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P.E. Metallurgy, Plymouth Tube

 

[Raai2015]

Hi any of you guys give me an any worked out example or any reference? With a given apology i am not welding expert though being process engineer!

 

[weldstan]

Not 2 14 Cr weld metal bur with F43 filler. By the way this has ben done numerous times prior to the greater use of P91/T91 for super heaters.

 

[weldstan]

Or is your client demanding the dissimilar weld be made with 2 1/4 Cr -1Mo filler metal? While this can be done, why would anyone want to? It places the weld metal as the greatest chance for failure.

 

[EdStainless]

Thanks for the catch Stan, I knew that 43 was the correct filler.


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P.E. Metallurgy, Plymouth Tube

 

[Raai2015]

It would be appreciable if anybody could let me know simple calculation for filler material / consumables selection for dissimilar welding. Just a brief introduction into the subject would be helpfull. As a Boiler process engineer , i was told to select step by step tube material (for eg : Carbon steel-T1A-T111-T22-T91-T347H). So if i understand this welding concept , it would be usefull. To be noted , just cheked the one of the project , WE as a company TP347H is welded with T11.

 

[raa2125]

Hope it could help.

 

[weldstan]

raai2015,
You keep saying welding tube with another tube. You weld T11 tubes TO T347H tubes with a welding filler metal. Because these tubes will be at high service temperature, they should be welded with one of the nickel based (F43) filler metal as per the KOBELCO table above to transition the large coefficient of expansion/contraction mismatch between the T11 and T347 material. This reduces the shear loads imposed on the joint during heating and cooling.

 

[Raai2015]

@Raa2125 : Thanks for sharing.
@ Weldstan : Apologise i didnt use the proper terminologies. In the boiler process design we were asked to select in this order. But what i am looking for is Let take an below example from above welding handbook
Welding T22 with T11 : Filler material E8016-B2 & ER80S-G If i am right how should i calculate This base metal is the perfect match. As an engineer i can understand better if there is any workedout calculation!
Reg
Baskar

 

[weldstan]

For welding T11 to T22 the use of E8016-B2 is the best choice. You could also choose E9016-B3. The ER80S-G should only be chosen if it essentially meets the chemistry of the E8016-B2.