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Hot tap at a pipe butt weld

Hot tap at a pipe butt weld

Hot tap at a pipe butt weld

(OP)
We were going to hot-tap a new 12" branch into an existing 24" on-site (non DOT) fuel oil pipe line.  When we removed the pipe insulation we found a butt joint right there.  The line can't be taken out of service for a tee and we can't move the tap because of other interferences.  The solution proposed is to weld on a split tee, then flange the tee and drill into the 24" pipe.  The question is: does B31.3 allow or dis-allow this?  Thanks...

RE: Hot tap at a pipe butt weld

Yes, I believe that ASME B31.3 does allow a "Split-Tee" Hot Tap for just such a situation.

RE: Hot tap at a pipe butt weld

(OP)
I am looking at the 2006 version and can't put my finger on it.  Can you point me there?

RE: Hot tap at a pipe butt weld

The linked site certainly indicates B31.3 allows split tee hot taps - http://www.teamindustrialservices.com/prp/pdf/hottap.pdf. Regarding crossing circ welds - Para 341.4.1 touches on examination requirements when circumferential and longitudinal welds meet. I think provided the existing butt joint is fully radiographed to ensure no defects, then it shouldn't be a big deal.

Just my thoughts,
John

RE: Hot tap at a pipe butt weld

(OP)
John - thanks for your thoughts.  I have no way of knowing if the circumferential joint was x-rayed, in fact I doubt if it was.  If this is a hard requirement, it will get expensive and time consuming.

RE: Hot tap at a pipe butt weld

I have generally followed the advice provided by IFRs for any intersection longitudinal and circumferential welds.  I would grind the weld flush and 100% radiograph to a minimum of 50 mm beyond each side of the opening.

If it is not possible to radiograph, I wonder if the code might permit other forms of examination such as UT ?

RE: Hot tap at a pipe butt weld

Modification is not mentioned in para 300(c) when B31.3 states that the Code only needs to be optionally applied to piping that has already been placed in service, but......

There would seem to be some wriggle room anyway in para 341.4.1(b)(1), in its reference to para 344.7, which basically allows visual examination to be undertaken. You know the job though, and how comfortable you would be with that.

RE: Hot tap at a pipe butt weld

Comfort level with hot taps is directly proportional to distance.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Hot tap at a pipe butt weld

I think I'm far enough away.

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