maximum size of hot tap branch on 32" line 1

[Bohlool]

Hi
We are considering hot tapping a branch connection to a 32" x 20.6mm THK pipeline.
what is the largest branch size applicable? is it possible to make an equal connection?
thanks,
Ashkan

 

[pennpiper]

Bohlool,
You do not say where you or this project are located or if you have contacted and had discussions with a reputable and qualified Hot-Tap Contractor.

Talking to an expert is your first step then the rest is in the details.





Sometimes its possible to do all the right things and still get bad results

 

[McDermott1711]

Link

 

[Bohlool]

dear pennpiper and McDermott1711
thanks for your attention.

it is a 32" x 20.6mm THK 600# sour gas service, design code asme B31.8 in Iran.
we are at early stage of decision making regarding making a hot tap or cold cut. as reduced size connection will lead to lower flow to the branch line, I need to know if it is possible to make hot tap connection equal to run pipe? or what is the biggest connection possible?
by the way, the contractor have suggested 26" hot tap connection, which we are not convinced with such reduction in size.
I'll be thankful if you share me your experience in this regard.
thanks

 

[TD2K]

I would expect you should be able to do a size on size hot tap though you'll need to use a full encirclement saddle. I do not know if there are any code issues, you'll need to research that especially in sour service. One concern with full encirclement saddles is there is a void space filled with the fluid which becomes a dead leg and corrosion concern.

A 26" hot tap on a 32" pipeline with the wall thickness you gave (guessing at the thickness required for the 26" pipe and how big of a coupon a hot tap machine could take out) should leave you with a beta ratio of about 0.78. That's about the upper end that my instrumentation people like to size an orifice meter for, have you done any calculations to see if the pressure drop (I assume that is your concern) really is a problem? If that is the issue, hot tap a 26" tie-in and then increase to the 32" or whatever size you want to run.

From a safety point of view, I would also prefer to take the line out of service and do a cold cut and weld in my tie-in.

http://www.ogj.com/articles/print/v...tap-installed-on-operating-sour-gas-line.html

Lot smaller pipeline than you are talking about but it discusses some of the issues they faced.

 

[McDermott1711]

If you insist on 32" branch and there isn't possibility of a cold cut, so, how about making two, say, 26" hot tapping which connect together at the downstream to form a 32" line?

 

[bimr]

The rule of thumb is no more than 70% of the run's diameter. ASME Code and EU code indicate that additional reinforcement of the main branch is required if the diameter ratio exceeds 0.7 : 1.

The minimum pipe schedule, type of piping material, and the orientation of the tapping machine must also be evaluated. Only an experienced hot tap vendor will be able to look over the scope and tell you if it is feasible. Call one of the hot tap vendors: TDWilliamson, TBL, Claxon, or Plidco.

 

[Bohlool]

thanks bimr, TD2K, pennpiper and McDermott1711
I think it's better to make cold cut for that equal branch out.
thanks again for your attention