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9 comments
Power-User

Join Date: Mar 2009
Posts: 125

Natural Gas Main Pipe Tapping

04/21/2009 6:06 AM

Dear all Gurus,

I have seen natural gas company was tapping the grid pipe line without shut off the supply stream.

Can anyone explain to me how they can drill,weld in order to install an additional outlet from main line.

Thanks

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#1

Re: Natural Gas Main pipe tapping

04/21/2009 6:19 AM
  • Attach T-clamp around the outside of the line, configured so that a flanged side-branch is presented.
  • Attach a full-bore flanged valve onto the branch.
  • Fit a hole-saw cutter onto a flanged drilling machine.
  • Bolt the drilling machine onto the valve so that the cutter will pass through the valve port.
  • Open the valve.
  • Drill through into the side of the live pipeline using the drilling machine and the hole-saw.
  • Withdraw the hole-saw through the valve, preferably removing the "Pringle" -shaped piece of pipe wall that the hole-saw has removed.
  • Close the valve.
  • Unbolt the drilling machine.
  • Crack the valve to blow out any swarf from the drilling operation. Shut it again.
  • Bolt the branch pipework onto the valve.
  • Pressure-test the branch pipework.
  • Open the valve and purge prior to bringing into service
  • "Robert is your mother's brother".

The process is sometimes called "hot tapping", and needs ideally to be carried out by specialists in the field. These specialists have ready access to the specialised equipment needed for the job.

The technique runs the risk of leaving swarf in the pipeline that may need to be strained out before it hits delicate equipment downstream.

A simplified and scaled-down version of the technique is sometimes used as a cheap-and-nasty way of plumbing-in a domestic washing machine. The Pringle stays in the pipework, and can be a b*gger that causes future maintenance problems elsewhere in the system (been there, T-shirt now on eBay...).

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Guru

Join Date: Aug 2007
Posts: 1803
Good Answers: 87
#2
In reply to #1

Re: Natural Gas Main pipe tapping

04/21/2009 7:06 AM

Very well put PW... nothing more to be said, and a GA from me.

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Power-User

Join Date: Mar 2009
Posts: 125
#3
In reply to #1

Re: Natural Gas Main pipe tapping

04/21/2009 7:20 AM

Dear PWSlack,

Thank you very much for GA.

Regards

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Guru

Join Date: Dec 2008
Location: nj,usa
Posts: 1084
Good Answers: 27
#6
In reply to #1

Re: Natural Gas Main pipe tapping

04/21/2009 9:16 AM

Can you be a little more specific? My mother's brother is named Jerry. Who is this Robert of whom you speak?

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Engineering Fields - Mechanical Engineering - New Member Technical Fields - Technical Writing - New Member

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#4

Re: Natural Gas Main pipe tapping

04/21/2009 7:25 AM
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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain - possibly to become "South Scotland" or "Non-Caledonia" from September 2016. Kettle's on.
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#5
In reply to #4

Re: Natural Gas Main pipe tapping

04/21/2009 7:50 AM

Spot on! Furmanite (usual disclaimer) are a good choice for this sort of stuff.

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Associate
Canada - Member - New Member

Join Date: Feb 2008
Location: Muscat, Sultanate of Oman
Posts: 54
#7

Re: Natural Gas Main Pipe Tapping

04/21/2009 10:59 PM

As far as oil and gas pipelining is concerned the world specialist is T D Williamson for both hot tapping and stoppling.

chama

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Power-User

Join Date: Oct 2006
Posts: 123
#8

Re: Natural Gas Main Pipe Tapping

04/22/2009 10:07 PM

aikh we used to work with the Mueller Company working with their line of hot tapping/line stopping equipment. Loved the work. Line stopping was used to shut down a section of damaged pipeline and at same time energising a pre installed bypass line (this is important since gas companies did not want to disrupt flow to customers). A bottom out or side outlet fitting allowed us to preinstall and test a bypass line. Once this was done the line tapped and when the cut was finished the new bypass line was energised. We could then cut out the damaged section of pipeline and cap it. Another application was to install a flanged service tee to add a service line to an existing pipeline to new customer. The service tees are installed with run of tee contacting the pipeline and the branch connection provided a welded connection to the new service line. Once the cut was made gas flowed to the new service. The shell cutter and pilot bit are designed to hold the coupon (or pringle) cut from the pipe. The Mueller shell cutters provided a surface inside the pipeline to seat the line stopper to shut off the gas flow. Holes in the shell cutter allowed gas to continue to flow while the cut was made.

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Guru
Hobbies - DIY Welding - pipewelder

Join Date: Apr 2007
Location: North Georgia, USA
Posts: 672
Good Answers: 33
#9

Re: Natural Gas Main Pipe Tapping

05/01/2009 10:13 AM

I have done "hot taps" many times in the past on many different services including gas, steam, water, oil, and many types of chemicals. First thing I would suggest before any welding is done is to have UT thickness of the trunk line to determine there is ample thickness to keep from burning through when welding. Next you weld a nozzle with a weld-o-let with a flange onto the live trunk line bolt a gate or full port ball valve on the flange and attach a "hot tap" boring machine to the valve. Drill the hole and retract the bit and close the valve. A hot tap boring machine is made to do this procedure and to hold the sudden pressure that will be seen when the trunk is penetrated. There is not usually a problem with this procedure unless and inexperienced welder burns through the trunk while welding. A welder that knows what he is doing knows how to not to over heat the trunk line by keeping the "heat" of the weld where it should be in these cases (on the weld-o-let) This does not need to be a dangerous project but it can very easily be made into a safety catastrophe without the proper safety precautions. I would suggest you get a professional company to do this type work and not take safety chances.

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Users who posted comments:

aikhh (1); AUREL MARES (1); chama2633 (1); not so smart (1); pipewelder (1); PWSlack (2); roadapple (1); Steve S. (1)

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