Welding Deformations - Split T 1

[Al83]

Hi All,
I do fabricate split tee fittings for hot tapping operations. They give me a big headache due to excessive deformations although heavily supported before welding starts.
I roll those in 2 x half circles. One of these halves has the branch and flange welded on top. They are all thinner than 1.5in in thickness hence PWHT is not applicable.
Any idea of how to get rid or reduce deformations for this application? Is heat treatment after welding can be considered as an option? Or you reckon PWHT will still be a good option for thin plates?
I have attached a photo of what a split tee is.
Any suggestions, help or references/books will be highly appreciated.

 

[LittleInch]

What I meant was make up your two half shells, weld them together with some length of weld - say 30% of the length - then cut the hole, attach your nozzle and then maybe heat treat before you cut the welds back off
Working on a half shell severly reduces the strength of your material.

I understand you're using non standard pipe dimensions for a half shell encircling split tee.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Al83]

Hi LittleInch
I am currently welding the branch on shell before cutting the hole as I have a very large boring machine, i can simply machine them to size on the inside after oxy cutting the hole.
I have not tried to open the hole first to be honest as i always thought that the uncut hole will provide some more strength to the shell (just a thought not based on any calculations or try and error).
Do you think cutting the hole first have a benefit in reducing deformation?
I will make a dummy piece and try it soon I think.
Thanks in advance.

 

[Ehzin]

I need to look at the above discussion in more detail but is it feasible to fabricate your split enclosure just by splitting the relevant pipe size versus rolling plate?

Thanks,
Ehzin

 

[Al83]

Hi Ehzin
No it is not possible since it is larger than a standard pipe.

 

[r6155]

Al83
You are welding from one side. Avoid that
Try to use neck insert through the shell wall, hence you can weld from both sides (bevel type K). The welding volume is less.
Preheat 80ºC prior to thermal cut the hole.
Preheat and maintain at a minimum temperature of 100ºC during welding.
Be careful with sequence during welding.
Fillet weld maximum 9 mm.
Do the hardness test on base plate near the hole before and after welding.
NO PWHT.

Finally, what code are you using?

Regards