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Welding on a pipe filled with cold water
8

Welding on a pipe filled with cold water

Welding on a pipe filled with cold water

(OP)
Is it possible to achieve a weld on the outside surface of 36" diameter 1/2" thick pipe while it is filled with water?

Thank you     

RE: Welding on a pipe filled with cold water

Sounds dangerous. Drain the pipe so that it doesn't explode due to the pressure increase.

RE: Welding on a pipe filled with cold water

The water will heat up and drain any heat from the weld away - so you won't get the heat you need.

The water may turn to steam and blow your head off.

RE: Welding on a pipe filled with cold water

Not much chance that welding on the outside of big pipe full of water will cause any pressure increase.

But it will suck the heat out of the weld zone far faster than the welder can put heat in.

The result will be lack of penetration and fusion and a bad weld.

RE: Welding on a pipe filled with cold water

It depends on a few things;

1.  Is the water moving or stagnant?
2.  How big of a weld are you asking about?  I would guess that it is not the full circumference of the 36" diameter pipe?

RE: Welding on a pipe filled with cold water

Quote (MintJulep):

Not much chance that welding on the outside of big pipe full of water will cause any pressure increase.

I was envisioning a smaller pipe, but it doesn't sound like a good idea regardless. Whether it bursts immediately or produces a poor weld from lack of heat (possibly bursting later), it is almost certainly a bad idea. The right thing to do is to drain the pipe.

RE: Welding on a pipe filled with cold water

(OP)
That's what I thought and wanted to hear.  
Thank you all
 

RE: Welding on a pipe filled with cold water

Bad practice, for alot of reasons, not the least of which is a high probably of underbead/delayed cracking with cellulosic consummables   

RE: Welding on a pipe filled with cold water

What is the temperature of the water and what, exactly, is the type of weld to be executed?  Hot welding on live hydrocarbon pipelines is common enough to give a pointer to welding on water pipelines.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04
 

RE: Welding on a pipe filled with cold water

(OP)
SEWER WATER AT ABOUT 50 F
THE WELD WILL CONNECT A BRKT TO RESIST APPROX 40 K OF THRUST FORCE AT ABOUT 6 TO 8 ECCENTRICITY (240 K-IN TO 320 K0-IN MOMENT)       

RE: Welding on a pipe filled with cold water

Put a good enough weld on there to stop the leak.  Grind it down and put a repair plate over it and fillet weld around the plate.

RE: Welding on a pipe filled with cold water

I agree with SJones on that point.  Not a common practice, but done often enough non the less.

RE: Welding on a pipe filled with cold water

sigma1525
Welding procedures can readily be developed and implemented to make the weld safely and to produce a sound, reliable joint. You will need to determine remaining thickness of the pipe at the proposed connection(s). It is assumed that you know the specification/grade of the pipe.   

RE: Welding on a pipe filled with cold water

Sorry..didn't see the explanation of what it was before posting. Thought it was a leak repair.

It is workable, just as stanweld and others have noted.  Proper procedures.  No different than welding cold steel in the winter.

RE: Welding on a pipe filled with cold water

Just don't burn through.....

rmw

RE: Welding on a pipe filled with cold water

The process is called welding with water backing, and yes, it is done.

RE: Welding on a pipe filled with cold water

Agreed that a welding procedure can be developed for this application.  

Test loop information as well as welding procedure qualification guidance can be found in API 1104 Appendix B.  The caution is that heat input calculations based upon flow conditions will need to be performed prior to actual production welding to insure that the weld can be properly made.

RE: Welding on a pipe filled with cold water

if the water is stagnant, we use a freezer unit to freezer the water further up the line (obviously it has to be a fair distance from the area to weld). That way you can work on a live water line. Happens quite a lot at sea on grey water / sewage lines.

RE: Welding on a pipe filled with cold water

Sigma1525,
We are assuming that your pipe is carbon or alloy steel and not ductile iron or lined steel (depends on liner).  

RE: Welding on a pipe filled with cold water

If you can weld under water (and you can), welding a piece of pipe full of water should be comparatively easy, shouldn't it?  Provided the material is weldable and proper procedures are developed, of course.

RE: Welding on a pipe filled with cold water

I have to eat a bit of crow here. In the initial comment, I was assuming (you know what happens whe you assume) a pressurized pipe carrying process water. For a high-strength weld, you'd want to back-gas it, so water... probably isn't your friend.

A sewer pipe has essentially no pressure load to fatigue the weld, so based on the comments above you're probably fine as long as you understand the loading and the are able to quantify the degraded strength of the weld.

RE: Welding on a pipe filled with cold water

I recommend you ask the welders at the AWS forum.  These guys do this all the time.

RE: Welding on a pipe filled with cold water

Not exactly the same situation but when I had a leak in my gas tank, they filled it with water prior to welding.  But the gas tank is made of sheet metal and any water pressure buildup was vented through the open fill tube.  Interesting process, though.

Bo

RE: Welding on a pipe filled with cold water

2
Welding on the water filled pipe that is 36 inches in diameter and has a 1/2 inch wall thickness can be performed; however the type of base metal is going to influence the mechanical properties of the weld and adjacent heat affected zone.

If the pipe is low carbon steel the results should be acceptable, but as the carbon equivalence increases, the hardness of the heat affected zone will increase from the rapid absorption of heat by the water which will result in increased amounts of martensite.

You can minimize the amount of untempered martensite in the HAZ by using a butter layer technique. The technique employs a layer of low hydrogen weld deposit on the 36 inch pipe as the first step. The actual weld deposited to join the members is deposited in a manner that will temper the HAZ of the initial weld beads deposited, i.e., the butter layer. It is imperative that the last weld beads deposited do not impinge directly on the wall of the 36 inch pipe to prevent the formation of untempered martensite once again in the 1/2 thick base metal.  
  

Best regards - Al  

RE: Welding on a pipe filled with cold water

In the natural gas pipeline industry, it's fairly common to weld branch connections to live lines while flowing gas.  The joint configuration we use is in API-1104.  The electrodes normally used for live line welding are E-7018.  Take a look at all of this then consult a welding engineer with all the variabls of your project.

RE: Welding on a pipe filled with cold water

Olefazz is exactly correct.  Welding on a wet line is regularly done.  If the fluid is flammable, assure adequate flow -- API-570 and 1104 will give guadance on that.

You only have [filthy] water.  Just ensure that pressure cannot accumulate.

Then conduct a Ultrasound survey of the proposed weld location to ensure sound metal thick enough to be weldable.  I use 3/16" for a minimum.

Weld using E7018 electrodes ONLY.  The celoustic rods that Eddycurrentguy warned against are 6010 and a few others.   Use 7018 only.  Stay with 3/32" diameter rods to control the heat input, even though it takes a little longer to finish.
 That's it!  Again, this is well-tested, and documented in API.

RE: Welding on a pipe filled with cold water

Other suggestions include using E8018-C2 electrodes which have good impact properties.  These electrodes operate really well, have a low affinity for hydrogen,  and the final weld, if properly applied via a qualified welding procedure, will yield positive results.

The butering technique suggested by GTAW is a great one...can be labor intensive, but, if properly applied, is well worth the efforts.

For in-service welding, I suggest the wall thickness be 0.250" minimum....thats the standard that several pipeline companies have used in the past, althought the material grade, OD, and flow conditions will need to be factored as well...  
 

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