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TOPIC: Welding of Valve to Valve

12 years 7 months ago #7248

  • banerj1s
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Friends,

Is there any apparent disadvantages in welding a valve to a valve? Due to extreme shortages of spaces specially near the condenser in a power plant the stop valve and the quick closing check valves are welded to each other in some of my earlier projects.
I would appreciate any expert comments on this.

Regards
Sudipto

Welding of Valve to Valve 12 years 7 months ago #4383

  • Jop
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If we think about this logically we should have an answer.

In piping you can normally weld any one object to any other object with no problem as long as there is no interference caused by something in or on the two objects.

That means that you can weld:
- Pipe to pipe
- Pipe to flange
- Flange to flange
- Fitting to fitting
- Fitting to pipe
- Fitting to flange
- Fitting to butt weld valve
- Pipe to butt weld valve
- Flange to a butt weld valve
And since these are "Butt Weld" valves, you can weld on the valve body.

So, if there is no interference caused by one or more of the valves internals or top-works then you should be able to weld them valve to valve.
Do it once and Do it Right

Thanks Jop. I didnt get 12 years 7 months ago #4384

  • banerj1s
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Thanks Jop. I didnt get many to agree on this because they think that it would be impossible to retrieve the valves at a later stage because they have to cut the valve in case of maintenance. But my experience says that big valves of 20" steam service should not develop problem on the valve body for at least 15 years. Even if they do valves are rarely cut. The welding is done at the spot itself.
The quick closing valves are swing check and it is followed by a gate valve. So no clash of internals are expected.
Hope for your comments on this.

Cheers
Sudipto

take care of soft internals 12 years 7 months ago #4385

  • raghurambathula
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take care of soft internals which may be damaged due to heat generated during welding

Hmmm ...so you’re fighting space 12 years 7 months ago #4386

  • 11echo
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Hmmm ...so you’re fighting space and still need a block valve with a check? Could you use a "stop check valve"? This valve is a combination of both, where you can get a bubble tight closure like a globe valve, but with a piston type check valve. I've used them afew times where we were looking to save money but have both capabilities. The only question would be "if" the piston type check valve would quick acting enough for you? Here's a link for a look see:
http://www.tpub.com/content/constructio ... 65_126.htm

Thanks for the post 11echo. 12 years 7 months ago #4391

  • banerj1s
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Thanks for the post 11echo. I really thought about it for long. But lets understand the operation here. The stop valve is actually to isolate the heaters from the Turbine in case of Heater Failure or turbine trip on the Steam water cycle of a power plant. The check valve would prevent any backflow of the water back to the Turbine and has to close within a split of a sec or risking severe water damage to the Turbine. I am not sure if a stop check valve can also be a quick closing valve operating at high temperature and pressure working on a steam sytem. As far as I know they are manual valves and some projects they are used in HVAC.
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