DON'T hot tap any line if you do not have the engineering data, procedure and equipment to do so.
DO use caution with any hot tap, regardless of the line service. While it is "just" a chillwater line, be prepared.
Are there any particular codes that need to be followed? What type of engineering data would you be refering to. Is it ever too cold to weld? Is a typical tig welding proceedure ok for this type of welding.
Have you ever performed a hot tap?
If you need minimum suggested requirements for hot tapping contact Global Engineering documents and purchase a copy of API 2201. This publication gives guidlines for a hot tap procedure, along with a hot tap checklist. Also the owners of the equipment should be involved and have engineer approval. good luck and have a good one!
There was some discussion on this forum a while back on hot tapping. Use the forum's Search function and type in "hot tap", change the days to 999 and the number of hits to 100. It should find those discussions.
Be safe, follow the good advice you are receiving, and get all your ducks in a row before diving into this. Subject not to be taken lightly.
John Wright
Do-Contact T.D. Williamson Co. in Tulsa. They can assist you with everything you need (training!) to do a hot tap or they can do it for you through their Services Department. They have service centers throughout the US and respond rather quickly.
I don't suggest doing any hot tap without training before hand. It can be very dangerous and expensive when the tapping proceedure isn't followed.
Don't- hire the cheapest guy in town or at least ask to see his job history.
Don't- do it your self if this is a one time deal.
Can you give more details i.e., What diameter is the carrier.What diameter is the branch (tap)? What is the wall thickness? What is the material, operating pressure, accessibility?
Ted
I have done numerous steamlines and condensate lines as well as chillers. I am working with sched. 40 carbon steel pipe with a diameter of 4"...the branch is 3"x4 weldolet...the pressure is at 60psi and it is wide open.
Thanks for all the help
Jeff G
Hey Jeff, again let a pro do it. BUT for conversational purposes you must start with the brand and model of tapping machine that is to be used.
Let's say you selected a TD Williamson T101 machine which has 18" of travel. The travel distance of the cutter is what is going to dictate how long your hot tapping weldment is going to be. I'm not going into great detail here because it would turn into a training session. Keep it as short as possible (weldment). Leave yourself as much travel on the machine as possible when calculating the lenght of the weldment. Don't forget to include the tapping distance in you measurements. Tapping distance is the distance the the cutter must travel from the point where the pilot bit touches the carrier to where it cuts completely through the carrier plus 1/8" extra. Finally the measurement are the most important thing in a hot tap (numbers DON'T lie). Tap to far and you might go through the back side of the main and not far enough and you end up with the coupon not cut all the way and the only flow you'll have will be from the 1/2" pilot hole. AND be sure to try the valve before tapping. Count the number of turns and record them. Be sure the valve closes after the machine is mounted. If you don't try the valve and the pilot sticks below the gate or ball you won't be able to remove the machine from the carrier.
******Do yourself a favor and check out TDW website******
Ted
I read this post and am curious what this hot-tapping device looks like. Is there a link somewhere online that shows one and how it works? Boggles my mind to think of welding a pressurized pipe and then making something flow through it without disrupting service anywhere in the system. This is what you're talking about here, correct?
bzzzzzzzzzzz,
It's not just pressurized piping, some contain explosive vapors and liquids. Makes me nervous to think about it. I would want to know if that is happening in my neighborhood, so I could take a vacation. Know what I mean?
Left to the pros, I think it has to be safer in reality.
John Wright
Doooooooon't worry, I have no plans on trying it, just wondering.
Take a look at Easy Tapper at
http://www.easytapper.com/
They have some smaller units for a low pressure job like yours. Some run with a hand drill. Most of these companies also have rentals.
A few months back when I was working at a local paper mill I witnessed a hot tap go bad. Nobody was hurt. The company that was contracted to do the job does nothing but hot taps. To make a long story short they drilled through the valves gate then through the pipe. This is the same company that had us rig there 800lbs machine up two flights of steps then install it before they found out the flow rate was to high for that machine. Just because a company does hot tapps does not mean they no what they are doing.
Maybe I'm wrong but I understand it like this: he has done numerous hot taps, but not specifically on a chilled water line and is requesting specific information concerning that application.
I've never hot tapped a chilled water line but I've welded several hundreds of hot taps, I did one today and have another one in the morning, both on gas lines. Any competent pipe welder that understands what he's doing, and how to do it (and this is all spelled out in the procedure), can weld hot taps. It's not something a piping contractor will have to call in experts for, it's part of what they do for a living. On your local gas distribution piping there will be close to one welded hot tap for every building in town, these are at lower pressures of course but still range up to 500 psi or so.
JTMcC.
I think you've got it nailed here. Probably looking for one of the metalurgical types who post here to advise him on the effects of the almost instant quench on the weld metal etc.
Bill
There is a lot of technical guidance available regarding welding on pressurized piping. A report and software available from PRCI (Pipeline Research Council International) allows users to determine what combination of weld heat input, preheat, and welding process (i.e., level of hydrogen) will result in a hardness that is typically associated with low probability of cracking. It can be used with a wide range of use-specified fluid types, fluid pressures, fluid temperatures, weld joint configurations, pipe thickness, and steel pipe compositions. (See http://www.prci.org/ then go to "pulications" and search pulications using the key words "hot tap". PRCI Thermal model for Hot-Tap Welding - V 4.2 Users Guide Rev. 3 is one of the latest, best resources) Appendix B of the 18th edition of API 1104 provides guidance regarding procedure and welder qualification tests for welds made onto pressurized piping.
I would not even consider hot tapping without a trained welder, a specially qualified procedure, and competent inspector who has the ability to monitor welder heat input and preheat.
I have welded several saddles on chill water lines for a hot tap. Several times the pipes were covered with condensation and I used GTAW process without any problems. That was several years ago and they have been in continue service without any problems. The last one I did was a 8" on a 24". I was stick welding using 3/32 electrodes. I was using as much amps as the rod would carry. Just after I was finished I was able to place my bare hand on the weld. Again the weld held, no problems. Ofcourse this was mild steel. Not really a big deal. The company I work for does all there own up to 4'' with a 1/2'' drill anything bigger they sub out. It is a good service to be able to offer the costumer.
That approach may be OK for water piping where the consequences of cracking are not likely to be severe. However, I would not advocate the use of uncontrolled procedures on a line carrying flammable or toxic liquids or gas. Susceptibility to cracking is very closely related to steel composition and not all "mild steels" or even grade B steel pipe are all the same. We have seen carbon contents for pipe range from about 0.06% up to about 0.30% or more with a similar wide range in carbon equivalent (CE). Low hydrogen processes like GTAW, GMAW, or low hy stick are beneficial, as is running as high a heat input as practical (high current, slow travel speed). Of course in thin wall pipe the heat input has to balance the probability of cracking with the probability of burnthrough (less likely with cold water inside).
A very interesting topic. I have done some hottaps , mostly for local oil & gas companies. Another contactor usually does the actual cutting/drilling. I always insist that the spot where the fitting is to be welded be checked for thickness/integrity with ultrasonic. Usually we accomplish the job without any actual written procedure, but they always do inspection (visual & mag. particle). Some of them really do cool fast, especially with fluid or gas moving through the line. Another thing that I noticed was the distortion ( egg shaping ) of a 3'' main line after we welded a 2" weld o let on it. Probably a good thing it was a low pressure service. My 2 cents worth. I sure enjoy the good reponses from all.
A lot of old small diameter grade A, or B steel pipe typically used in oil and gas has a composition that is very resistant to hydrogen cracking, so you can often get away with just about any preheat and heat input. In thicknesses less than or equal to about 0.219 inch (or even 0.250 wall in some cases) the biggest danger is from burn through from using too much heat input. Its so easy to come up with a technically defensible procedure that ensures use of an appropriate range of heat input and preheat for a desired welding electrode selection that I can't see leaving it to chance. Fixing cracks takes time and money. A failure is even more expensive and represents a huge and avoidable liability. Its much easier to do it right the first time. I suspect a lot of small pipeline operators don't have the technical expertise on staff to even recognize the danger in what they are doing when they don't use properly qualified procedures that follow the guidance of documents like API 1104 appendix B.
I don't think there is anybody out there operating pipelines or distribution systems that doesn't know and understand that you have to have a written procedure for any weld made on the pipe. Even if the welder doesn't see it, it has to be in place. DOT and the state agencies demand it.
JTMcC.
lam check pipe(laminated pipe) cooling flow rate test(basically heating pipe in one area and finding out how long to cool down to a specified temp) thickness test this is not the same as a lam check heating while welding with a torch that will keep carrier pipe warm enough for welding
type of rod to be used full penetration root? hot pass rod? filler and cap rod? post heat now lets think about tapping right valves, machine cutters,travel( to get drill out after youve tapped so you can close valve) sounds like an engineered job to me be carefull i myself have done and been on jobs stopping and tapping from 6oz to 400+lbs and what can go wrong sometimes will dont forget non distructive testing
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