Hot Tap: When would a backing ring be needed? Valve test? 2

[iangineer]

I am working on updating the hot tap procedure for my company and one of the comments on updating is that the question of using a backing ring always comes up. I can find very little on the use of backing rings for hot tapping.

Question 1:
Should backing rings ever be recommended? If so, what would be the circumstances?

Question 2:
The valves are to be tested to be "leak free." Should I specify that they be seat tested per API 598, or is there another type of leak test that would be more appropriate?

Thanks in advance.

 

[1503-44]

Backing rings keep weld material from dripping or from blowing out the back side of the weld

https://amarineblog.com/2019/09/06/backing-in-welding/

I think you would want the API seat test for hot tap valves.

 

[alchemon]

To answer your second question, it depends. Are you the operator of a pipeline or manufacturer of the the tapping valve?

If you're the operator:

Most of my clients "leak test" the completed fitting at the line pressure if there are concerns about putting the full 1.5 x MAOP (or at least the code minimum) against the existing line. Otherwise, if there are no concerns, then it is "pressure tested" at the full amount as pe code minimum to substantiate MAOP.

I would recommend that in your procedure, you should note that company engineering should be consulted for the test pressure on a case by case basis. This matches most of the clients/operators that I work for.

 

[pmover]

refer to API-2201.

to clarify, the "leak test" on the valve/fittings, etc. should be done prior to cutting the hole in header pipe. this test include all fabrication and all welds prior to placing the tap into service.

 

[SJones]

Please clarify the specific equipment to be hot tapped. For pipelines, the only backing should be the strip behind the longitudinal weld of the split sleeve/tee.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[LittleInch]

I was confused by the backing ring quote.

Can you define a bit more where you use a backing "ring" on a hot tap. Backing strip for sure as S Jones says. Kind of depends how close you are to the hot tapped pipeline with your weld and if there is any issue with welding that close. I guess is tops the split tee from becoming tacked to the other pipe, but otherwise I would just engineer in a small gap.

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

 

[iangineer]

Question 1:

the only backing should be the strip behind the longitudinal weld of the split sleeve/tee.

-That must be what is questioned in the comments I have. We have an existing Hot Tap procedure, and I am just updating it based on a collection of comments I've accumulated. A backing ring for the longitudinal weld makes a lot of sense.

Question 2:
-The procedure currently states that "the valves shall be tested and certified leak-free by a (company approved) valve test shop." I took that to mean that the valve needed to be sent off to a shop for leak testing, but I guess it could also mean they could field test it as part of the completed fitting?
-Procedure goes on to state that Special valves needed for stopples will be purchased by the company and shall be tested by the approved valve test shop prior to being issued to the contractor.
-It was also questioned if the valve needed to be painted yellow on the upstream side once tested. My understanding is that it doesn't matter which side is upstream or downstream in valve orientation and painting yellow would be unnecessary.
-Other than specifying the "leak test", does that seem clear to y'all?

Side note on my spelling of "y'all": It's marked as an incorrect spelling and a suggested correct spelling is "yawl" lol

 

[alchemon]

For question 2, if you are buying an API stamped permanent valve, the manufacturer should be able to provide evidence of a shell pressure test (same as pipe being tested by the mill). If not, you need to buy a different permanent valve. If you are talking about a sandwich type valve used in the tapping machine itself, generally those are not pressure tested by the pipeline operator as it is generally used temporarily and contractor provided. However, the manufacturer should be able to provide evidence that the valve in the tapping train has been tested to at least whatever flange rating they have put on the valve.

You could in theory shop weld/test the stopple/valve assembly and then bring it to the field. A field test is going to be needed for the fillet/connecting welds used to connect the stopple onto the existing line. In my opinion, which is done is more case by case/contractor convenience for ease of constructability.

If you are smart, you can full MAOP pressure test the connected permanent bypass components (fittings and pipe you are using to alter the existing pipe alignment), and then you are only left having to leak test the stopples et al and the joining welds between the stopples and permanent bypass piping. Obviously as previously mentioned, this needs to be done before you tap the existing line.

Don't forget to add a blurb to soap test the completion plug/flange once the tapping is done.

How it is painted is irrelevant and company specific, so follow your own O&M procedure.

 

[SJones]

It won't be a "ring" - it will be a strip. Try consulting EEMUA 185

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[iangineer]

It won't be a "ring" - it will be a strip. Try consulting EEMUA 185

It seems I don't have access to an official copy of EEMUA 185. The wording in the comment specifically said "ring", so is there any place else a backing ring would be used for a hot tap? I'm thinking it might have meant "strip".

Thank all of you again for all the help!

 

[SJones]

I can't think of any hot tap configuration on tubular equipment that would accommodate a "ring'

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[iangineer]

This post is to share an update for anyone looking for information in the future:

API 1104 Annex B has information on welding to in-service pipe. In reference to my Question 1, Sec B.4.2.2 states that the longitudinal groove seam welds "should be fitted with a mild steel backup strip or suitable tape to prevent penetration of the weld into the carrier pipe." and includes a note: "Penetration of the longitudinal groove seam weld into the carrier pipe is undesirable since any crack that might develop is exposed to the hoop stress in the carrier pipe."

hottapforum.com has a thread on backing strips and most of the posts including one from TD Williamson notes that their standard back-up strip is 1" x 1/16" and the TD Williamson fittings have a groove machined to accommodate the backing strip. That would remove the gap that could possibly be caused by the backing ring.