Condition of the valve during installation
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Hello everyone, for valves with flange (threaded) connections and welded valves, should they be in the open or closed state during installation? Why? Thank you.
I remember it was necessary to turn off for threaded connections. It needs to be opened for welding. It was mentioned in the constructor’s textbook.
It should be possible to connect it directly; just connect it in its original state from the factory. To open the valve, external force is required (pneumatic or electric, etc.)
For valves with threaded connections, in the case of threaded gate valves and globe valves, closing the valve helps to increase its stiffness; whereas for ball valves and plug valves, it doesn’t matter whether the valve is open or closed. Valves with welded connections: for socket welding, the valve can be opened and closed ； For butt welding, the valve should be in the open position to prevent spatter and slag during welding from damaging the sealing mechanism. However, in some cases, isolation measures are taken during welding, such as placing barriers in the passage, allowing the valve to be opened or closed in either case.
The answer on floor 6 was good. The textbook states it this way; the reason is probably the explanation on page 6.
For valves welded by butt welding, GTAW is generally used, with virtually no spatter or slag.