Welding on a pipe filled with cold water 8

[sigma1525]

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

 

[flash3780]

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

 

[MiketheEngineer]

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.

 

[MintJulep]

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.

 

[DVWE]

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?

 

[flash3780]

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.

 

[sigma1525]

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

 

[Eddycurrentguy]

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

 

[SJones]

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

 

[sigma1525]

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)

 

[Ron]

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.

 

[DVWE]

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

 

[stanweld]

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.

 

[Ron]

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.

 

[rmw]

Just don't burn through.....

rmw

 

[metengr]

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

 

[Eddycurrentguy]

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.

 

[BrundLFly]

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.

 

[stanweld]

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

 

[moltenmetal]

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.