Definition of isolation valve

1 : in cluster tools, a mechanical component used at an interface plane to permit environmental isolation between the transport module and an attached module. There is always one isolation valve under the control of the transport module. [SEMATECH] 2 : in the pressure testing of fluorocarbon tube fittings, a valve used to separate high-temperature fluid from high-pressure fluid, or to separate the samples from each other. [SEMI F10-93]