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Gate valve strength in compression

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CrimsonEngineer

Civil/Environmental
Dec 5, 2008
10
Can anyone help with the the axial(compression) force a gate valve can withstand?

For a project I am working on we are cutting a 30" diamter cast iron water pipe and installing a 30"x12" reducer(or two reducers back to back) and then a 12" gate valve to replace a section of this main with 12" pipe. During construction we will temporarily need to provide thrust blocking for the reducer and closed 12" valve. The setup proposed is as follows: 30" pipe-30x12 reducer-12" gate valve-short section of 12" ductile iron pipe-12" cap-temporary concrete block-steel plate-existing 30" pipe. The temporary concrete block will later be removed and the 12" pipe extended.

The issue i am investigatin is that during this temporary configuration the thrust force on the reducer/closed valve will put the valve and short section of 12" pipe in compression between the reducer and the thrust blocking and i don't know if the valve can handle this type of stress. The thrust force is 83,000 pounds. Can anyone tell me if cast iron gate valves can handle this type of compression stress? The valve will not need to operate during the temporary scenario.

I am in contact with the valve manufacturer and am waiting for their response but was hoping someone on this forum may have experience with this question. Thanks
 
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Normally a valve in a pipeline is constructed to be installed as a component not to bear or transfer any force as a result from movements, weigts or loads or stresses from the pipeline. The pipeline should be supported and anchored, and the valve itself also supported, and pipeline and valve aligned.

The reason is to ensure proper function of the valve over time. If you permit loads from the pipeline you will have difficults both to be sure of the exact impact forces, torques and stresses for the valve.

In my opinion the best way is to ensure that the pipeline is ancored to take the load, and/or in addition mounted with a permanent extension piece with sliding properties (non- lockable) to take up the axial movement.

Even if the valve itself could in practise take a considerable load, I would not recommend this as a solution. Even if the factory (agains my belief) will give you a guarantee.

Good luck!



 
Thanks for the help.
FYI - The valve manufacturer I talked with confirmed that they have not tested gate valves in this scenario and could not warranty a 12" valve used in this configuration. They would however be comfortable with a 16" class 250 Butterfly valve for the temporary condition.

It was ultimately decided to not use any valve in the temporary condition and to install it after the permanent thrust blocking was in place.
 
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