Hello all,
New here, Mike from Chicago. Pipefitter for 30 yrs.
I have a little dilema, we're going to tie in a new 2 1/4 chrome sch.80 main steam blow-down header to an exsisting sch40 carbon steel line. No feasable way to purge the carbon line. New header was fabbed using ER90s and 9018. I know that wasn't needed, ER80s would have been sufficiant. Will ER70s for the root, and ER80, or 90 be ok for the rest of the passes for the tie in weld?
I'm just wondering about cracking.
All advise is appreciated.
Thanks,
Mike
Mike, Welcome to the Forum!!!!!!!!!!!
I don't think "chrome" tells us enough about the header to even begin to help with filler selection...
Also.. having been a pipefitter as long as you have you must be quite familliar with codes and compliance.. Is there no authority on your project that is providing welding procedures? What is the governing welding code for the work you are doing?
I would be wondering about cracking too if I were in your shoes :)
Sounds like somebody is trying to make you fly by the seat of your pants...
Tell us more about your project.
Mike,
It sounds like the new header is a A335-P22 or similar material. The ER90S-B3 and E9018-B3 would be needed for the matching alloy content, not the 90 ksi tensile strength. When welding P22 to carbon steel, the typical practice is to use the ER90S-B3/E9018-B3 so that the final weld metal winds up having some alloy content after dilution from the carbon steel. If you use the ER70S-2/E7018 there will be some slight alloy pickup in the weld from the P22 material, but not much. Having said that, there are many folks that use the carbon steel electrodes and have no problem. I'm assuming (perhaps incorrectly) that P22 was chosen for the blowdown header to be resistant to wall thinning from flow accelerated corrosion and not for its elevated temperature properties. My suggestion would be to preheat to 400 F, weld it with the ER90S-B3/E9018-B3 and don't worry about purging the root pass. Purging is not needed for the CrMo alloys with less than 5% Cr content.
To add to MBSims excellent response... Internal draft will be your greatest enemy. Sealing off ALL openings to minimize draft can be your largest challenge. Just the heat from your elements can create bothersome air flow through the root opening.
Have plant operators walk down the system and close the valves. Liability dictates Operations should be involved in any valve closures and openings. Or it's Visqueen and Duct tape time.
Mike;
We're dealing with a lot of 2-1/2 Cr on current project and as usual, MBSims hit it dead on the head. The only thing I might add is try a slow cool (wrapping or whatever) in addition to those suggestions from Marty. Depending on thickness, PWHT may be required.
The contractor that you are working for should have a Weld Procedure Specification (WPS) for joining P1 material to P5A material, this is the recipe to make the weld, it will out line Preheat, inter pass temp, electrode and filler material as well as purge if the WPS was qualified that way. without any other background info this may fall under ASME B31.1 and a WPS and PQR (procedure qualification record) will be required in the job document package. As well as the welder certs, up to date continuity, pipe mtrs and so on. And yes internal draft will be the enemy, but when you get done you can have a Genuine Draft!
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