When valves are closed to stop water flow in a pipeline, a thrust is generated along the direction of the pipeline. Hence, it is necessary to restrain the valves during closure to prevent it from moving in the thrust direction. If the closed valve is situated inside valve chambers, it is connected to a puddle flange embedded inside a wall of the chamber. As such, the closed valves can be effectively restrained from the thrust action during the closure of valves.
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This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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If the pipeline is restrained by the buried soil and the pipe connections are welded (carbon steel pipes) you may not require puddle flange, however you should ensur allowable flexibility at the pipe / wall connection and valve / valve support connection for more system durability.