It depends on the size and construction of the pipeline and the fluid inside it. For the smallest lines a bronze gate valve is 'cheap as chips', though the need to rotate the handle a number of times to get from open to closed may be an unattractive feature. A ball valve with a 1/4 turn from on to off may be more attractive, though of more initial value. Above, say 2in (50mm) diameter the butterfly valve starts to become attractive for the same 1/4 turn criterion; though a pair of flanges are required now, one either side of the valve, it may be a more appropriate solution than a ball valve, as now the ball is becoming quite heavy and the valve to contain it likewise. Plastic pipelines tend to gravitate towards ball valves and diaphragm valves; the value of a 4in (100mm) valve is little more than the value of a 2in (50mm) one.
What does the operation's local piping standard say on this matter?
For isolating a system for maintenance purposes, it is usual to lock valves and insert a spade in the pipeline at a sutable point under a Permit-to-Work system; valves are not considered a reliable-enough shut-off arrangement to assure downstream personal safety in most industries.
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