Answer / prem

in any application single seated valve permit 2 to 3% leak in full closure position advice to use double seated valve to ensure tight shut off.

Answer / praveen kumar

double seated valve-this type of valve used in high pressure line to minimze the force applied to the stem by process fluid pressure across the fluid.
Explanatioin:-there will be two opposed force vector, one generated at upper plug and another generated at lower plug. the plug areas are approximately equal, then the force will likewise be approximately equal and therefore nearly cancel. this make for a control valve that is easiler to actuate.

singlw seated valve used to low pre applications to control accurately

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