hot tap?

Date 05-29-2014 02:47

In short reply yes that is how you would do it in the field one to two butter passes and then lastly to the tap or sleeve. Maybe I will elaborate alittle more in a few days or some one else will chime in. But off to bed and tomorrow headed to Texas where I will be inspecting a few hot taps. Maybe I will see you out there? :grin:

By atc250r (**)

Date 06-01-2014 18:47

1st pass concentrate the majority of the puddle on the carrier, but still tie into the sleeve. 2nd pass all on the carrier, making sure to get have the proper leg-length from the sleeve. 3rd pass is on the sleeve and covering the 1st pass. 4th pass on the 2nd pass, leaving no less than 3/32" of that 2nd pass exposed BUT DO NOT TOUCH THE CARRIER. That 4th pass tempers pass #2. 5th pass covers #3 and ties in nicely to #4. That's the procedure for 12" and bigger that I weld to anyway. Yours may be different

By TRC

Date 06-01-2014 23:47

Short Stack, that sounds like that is coming straight from the TDW tapping sleeve instructions. Buttering is unusual. Need more info on what type hot tap fitting.

By Superflux (****)

Date 06-02-2014 09:27

Buttering the carrier first is a technique that makes a lot of sense to me. I think it is very prudent to butter the carrier to the full fillet weld leg length prior to tie-ing in to the sleeve. This helps ensure that any or most subsurface bead cracking would be on the buttered beads rather than pull out a chunk from the base metal (live line) due to the shrinkage stresses of welding the sleeve directly to the carrier in a continuous sequence layer after layer. But this is a procedure that should be approved by a real live Welding Engineer.
T.D. Williams has made thousands upon thousands of hot taps and they seem to know what they are doing.
Every Pipeline owner and project is different and the Engineer that puts his name and stamp on a method is the way it shall be done.
That being said, I have made hot taps on lines in the past (35+ years ago) that if under those same conditions today, I'd run/drive as fast as possible before some other gung-ho welder started stringing out leads.

By jarsanb (***)

Date 06-02-2014 17:35

Hot Tap welding procedures or "In-Service" welding procedures can vary quite a bit. It depends on a series of issues. One is the carbon equivalent of the carrier pipe and or sleeve. More conservative procedures would call out for buttering layers to be deposited on the main first, possibly ground down to a certain height (1/16" common) then the fitting positioned over this area. If your first buttering layer also contacts the fitting then additional filler passes may not temper the HAZ on the I.D. portion of that first pass leaving high hardness areas potentially. The welding procedure will specify the established pass sequence. The procedure should have been developed addressing issues such as carbon equivalent, flowing contents, service pressure and flow rate...among other things. The more severe the operating conditions or pipe chemistry the more conservative the welding procedure will be. So to answer your question directly, it all depends on pipe materials and operating conditions. I would have to default to the company established welding procedures.