Hot Tapping on Natural Gas Line

Are you aware of flow meters that can be strapped on the pipe to measure natural gas flow, and I think they are good enough to possibly be used for LACCT? In fact, if such a meter worked for you, you might not need to hot tap the line to install other devices (unless you are hot tapping for other reasons).

Your title alone gets me very worried for your safety and the safety of others around you. Tapping into an active natural gas line should only be done by knowledgeable authorized. Your new job title shows that you can get the authority. CR4 though should not be your knowledge source. Your colleagues should be your knowledge source.

Be safe.

I don't have a dog in that fight first of all. I was merely pointing out they may not need to hot tap the line at all, and in many cases hot tapping a natural gas line is not only way dangerous, it could be illegal. Especially if safety constraints at the location such as nearby population or other industry could be harmed if something went wrong. If all he wants to know is gas flow, there are ways to deal with that without breaking into the line.

By the way, what new job title are you referring to redfred?

Hi James Stewart,

redfred was not replying to you, but the OP (original poster). To reply to the OP, you click the Reply button In That Post. I replied to you specifically by clicking on the Reply button at the bottom of Your reply.

You can also see that replies to posts are indented from the left. Hope that clears things up a bit.

Thanks for pointing me in a better orientation.

Ignore this one

Is this a steel high pressure main or a plastic distribution main?

If steel you're on your own as far as I'm concerned.

Plastic you will use hot weld, the fitting usually has a built in cutter which acts as an isolation valve when screwed back in.

Hot taps on pipelines are not unusual; see this document with some stats from the US EPA

http://www.epa.gov/gasstar/documents/ll_hottaps.pdf

Pipelines carry gaseous or liquid money and are ALWAYS metered, usually at multiple points.

I can't possibly tell you what your company's flow rate for a particular segment of the pipeline is, but flow rate is a known at the metering points.

The suggested product (gas) min. velocity during welding of a hottap shall be 1.3 fps (0.4 m/sec), and no limit on max. velocity.

..................................

MR. ABDEL HALIM: Can you please give the source or basis of these values. As they are not mentioned in API RP 2201. I need some authentic source. Regards, Bilal awan (OP)

I'll second that request. Maybe I'm missing something, but I can't see what gas flowrate has to do with hot tapping.

Also in case there's any misunderstanding, I believe hot tapping is same as live tapping, ie tapping a working pipe. It doesn't (necessarily) mean thermal welding, though I believe that can be done. Natural gas in a pipe won't explode if the pipe is heated, as there is not a flammable mixture. Ethyne (acetylene) will explode per se, but that's another story.

Cheers.........Codey

These data were extracted from a standard specification of an Egyptian oil exploring co. which stated that the reference is API 2201, but unfortunately I didn't found direct clear figures for min. and max velocities.

But at API 2201, I found at Para. 1.2 Referenced Publications the following standard: Battelle Institute "Investigation and Prediction of Cooling Rates During Pipeline Maintenance Welding and Battelle's Hottap Thermal Analysis Models", which is available from American Petroleum Institute.

can you please help out to find the mentioned document. Battelle Institute "Investigation and Prediction of Cooling Rates During Pipeline Maintenance Welding and Battelle's Hottap Thermal Analysis Models", which is available from American Petroleum Institute.

If the natural gas line is your company's or a customer's you should be able to find out from personnel who are responsible for it either what rate the natural gas is being put into it or being taken out of it. That should provide what rate it is going through it.

If the line isn't your company's or a customer's you probably should go through the proper channels before doing anything further. In the US of A simply asking what rate of flow there is in a pipe line that you have no reason to be interested in can possibly get you in big trouble with the DOT, Homeland Security, and all sorts of badges with acronyms like FBI, DEA, etc., on them.

Hot taps must be done by skilled, qualified and experienced personnel only! Is any life worth the risk if something should go wrong?

Good Luck, old salt

Dear all

I fully agree with old salt that "Hot taps must be done by skilled, qualified and experienced personnel only!"

The limitation required for wall thickness is to avoid overheating and burn-through. also there are some precautions and factors need to be considered in hot tapping

1. base metal should be free of lamination at the area of welding hot tap fittings.
2. hot tap fittings should be tested to 1.1 of the internal pressure
   
3. min. and max flow rate in gas and liquid hydrocarbons should be considered
4. do not perform hot taps in stagnant gas and liquid hydrocarbons lines
5. Hot tap fittings (branches) should comply with ASME B31.3 (equal tee or weld out let WOL) depends on the size of the main and the branch.
6. metallurgy of main pipe and hot tap fitting and welding electrodes should be compatible.
7. use of low hydrogen and small diameter electrode as possible to reduce the input heat

These are some of many factors need to be considered.

Hot tap is a safe solution and very useful technology when it is done right, missing any of the above points could lead to unpleasant results.

I hope that the above clarifies the points of discussion.

There should be a written Process Description document and a set of design calculations to hand that have been used to size the line. Ask the local Process Engineer for them.