hand check valve VS check valve
hand check valve VS check valve
(OP)
Wondering what is the difference between hand check valve and regular check valve. and their applications?
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hand check valve VS check valve
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RE: hand check valve VS check valve
Hello cranstonbu:
If I have understood correctly 'hand operated checkvalve' is used (and in my opinion uncorrectly) to describe 'screw down non- return valves'. (Anyone : Please corrct me if I am wrong!).
Screw down non-return valves (which also can be motor or actuator operated) are checkvalves that will and can operate as normal non-return valves, under normal operational periodes. That is: the clack , disc etc. will close when fluid delta P over the valve reverses direction, closing for backflow of fluid in opposite direction to normal flow direction.
But: in addition to the normal operation by fluid force up and down, the valves can be forced to close down by the spindle screwed down: first part to overcome the free movement of the disc, and then (as a normal closing valve) forcing the closing element down and keep it permanently in closed position, until released by screwing up the spindle again.
Screw down non-return valves are far more seldom used than normal check-valves, as a high-quality non-return valve, correctly dimensioned and type-selected in most cases will be more then adequaate.
As a result screw down non-return valves are mostly used when the pipeline (or this part of the pipelin) is not in 'normal or regular use', and a backflow will have large consequences for instance for process, cost or environment.
Some applications and industries will have more 'normal' use of the screw-down non- return valves than others. For instance oil and gas (?).
RE: hand check valve VS check valve
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