Split Sleeve used for Hot Tapping onto a Gas Line

I recommend that if this is a flammable gas line then you do not use any material that will make a spark in atmosphere. Regardless of the gas in the line, if you require our input to validate you to drill into a gas line I say that you should not do this. If this uncertainty is just your personal uncertainty then ask your supervisors on how to hot tap a gas line. Hot tapping is not a field to take anonymous tips from a public forum. If you have to ask us, put down the tools and don't do it!

Hi Redfred,

I fully agree. You should only perform this operation with experienced companies who have a broad experience in hot tapping gas pipelines both in the mechanics of hot tapping and experience with gas line process. If your company does not have this experience you should contract professional companies that do this type of work.

We have successfully carried out hundreds of hot tappings on gas lines during the past. We also have an experienced hot-tapping team. This is the first time that we are using a pre-fabricated split tee (which does not get welded onto the carrier pipe from inside) as recommended by our designers. However the testing procedure is not specified in this case.

I don't think KOH (potassium hydroxide) is flammable, but still there are pressure and leakage issues.

I'm not sure how to test between the main pipe and the first valve next to the hot tap, but all the downstream piping could be tested (hydro or pneumo) before opening the valve. Radiography or other NDE should be possible, even if a pressure test is impractical.

Thanks for your input. After welding the split sleeve onto the carrier pipe we can test the stub before hottapping. The question is what pressure to use as normally we test sleeves with N2 at low presssure. In this case the sleeve is subject to the line presssure.

Interesting problem: This pressure test would impose external pressure on the portion of the main pipe enclosed within the hot-tapping tee/sleeve. A "normal" hydro test of 1.5 x allowable pressure might be too high? And even a "normal" pneumo test? That's a new one on me, so these are just some thoughts.

You have shown your experience on Hot Tapping but you are new on using SPLIT TEE on live line. This proves that you have no experience of welding and testing split tee on live line. If this is so I can give you my experience on the subject. Welding of Split Tee call for extra care in selecting location at live line, selection of electrodes, process of welding, sequence of welding and mode testing of welded assembly.

1) Select location on live line where there is no internal corrosion or erosion due to flow. This you can do with thickness tester.

2) Mark the point where you want to weld the split tee and clean circumferential girth where weld deposit is going to be fall.

3) Select an inch wide x 2mm thick mild steel strip, 1/4" smaller than the horizontal length of the split tee.

4) Tack weld this strip to internal side of split tee to work as backing strip on both horizontal weld.

5) Carefully align the split on weld location and tack weld both part upper and lower split tee to hold in position.

6) Weld on both horizontal weld simultaneously and complete the joint.

7) You would notice that backing strip is not visible at girthweld and make sure it does not happen.

8) Clean girthweld area and start welding with low hydrogen smallest size electrodes (3/32") for cellulose coated electrodes arc pressure is much higher than the low hydrogen and hence burn through is avoided. Low rate of heat input is safe.

9) You may deploy dye-penetrant testing on all first, second and last passes of weld deposits during welding.

10) Toe of the weld deposit on girth weld must not be less than the thickness of split tee.

11) Weld toe should be gradual and smooth.

12) Allow cooling of weld assembly.

13) Now Testing - the only effective testing is Hydrostatic Test. But if you do this water or moisture would remain trapped in assembly which is not recommended. Substitute this test with air,Co2 and other noble gasses at pressure according to classification of split tee ie. Class 150, 300 or so on. Test pressure 100 - 300 psi

14) If you to refer refer codes on this Job: API Recommended Practice 1107 for Welding and API Publication 2201 for Hot Tapping.

15) For all that success the Split Tee must have required classification flange.

I am sure that you must be aware that Hot Tapping Machines come with Flange 150, 300, 600 and so on. You must have matching Hot Tapping Machine with available Class of split tee.

16) Rest you are the Master of.

Refer API recommended practice 2201 - procedure for welding and hot tapping for equipment in service.

Hi,

There are many ways of making a branch connection. Hot Tapping is one way of making a branch connection while the pipeline remains in service. There are also a number of methods of making a hot tap.

There is in the industry some apprehension on making hot taps on gas pipelinesline. Nevertheless companies that have obtained experience in doing this have relieved this apprehension. There has been a lot of experimental work performed regarding hot taps on gas pipelines. Hot tapping involves cutting a hole in the operating pipeline and attaching a lateral connection. Cutting a hole in a pressurized pipeline will weaken the strength of the pipeline unless you provide some means of adding strength.

Using a split reinforcing sleeve installed properly will add to the weakened strength of the pipeline. Using a split reinforcing saddle is probably the best way of providing added strength both for pressure containment and for mechanical strength. However this should also be installed properly.

Hope this is of some help.

CB

Thanks. The carrier pipe and the branch are both 3" diameter. Thats the reason for choosing the pre-fabricated split tee. My apologies for not putting you in the full picture at the start.

The hot tap for main run diameter equal with the branch diameter is not quite simple, unless the hole in the wall of the main run is kept significant smaller than the internal diameter of the main run.

Else, there is a high risk either to cut from the wall of the main run, or to not be able to remove the coupon.

If you really need the branch size equal to the main run, it can be done but there is not "a hot tap" but 4 hot taps, ( two of them for temporary plug the section where you wish to install the branch and the other two for temporary reroute the flow until you will install the permanent equal tee - of course the temporary re-routing will have the diameter less than the main run , but I assume that for a while - until the permanent tee will be installed, it will not be a issue to the process ).