ASME B31.4_Split tee design_wall thickness allowance

[kiranrma]

Hi,
We need to design a hot tap tee for ASME B31.4 pipeline, We use the 404.3.5 to calculate the required reinforcement. The Design Factor = 0.5;Design Pressure = 149 Bar; Max. Temp=72°C;Weld Factor =1;Corrosion Allowance=0mm; Maim pipe ID/OD=717.2/827.2mm & Branch pipe ID/OD=566/626mm. we fabricate from plate to make the main and branch. Main pipe is 55mm thick & branch pipe is 30mm thick. In this case do we need to consider other allowances?
Thanks

 

[LittleInch]

I don't think 404.3.4/5 strictly applies here.

The key issue is that the pressure sealing weld onto the main header is the fillet weld at the end of the tee and hence the inner surface of the tee sees pressure which is only being resisted by that circumferential fillet weld. This stresses the tee differently than the ones described in the code.

I would be looking at an FEA of something that big and that much pressure.

Why are you not getting the hot tap company to design this tee? Then it becomes their issue if it doesn't work, plus they will have done this many times before.

hot taps are not something to do once, but my apologies if you're working for the hot tap contractor - you don't say.

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

 

[kiranrma]

@Thank you Littleinch.
We are fabricating the Tee for the HOT TAP contractor, the circumferential fillet weld is done by the contractor at the site, we give the required thickness as per ASME B31.4 402.3. we roll the plate to get the main & branch pipe, and then do the machining to achieve the required thickness. Can't do the FEA from our side.