Definition of "cross" purge

1. a configuration of purging manifold that incorporates three valves and an inlet connection for process gas . The three valves are a regulator isolation valve, a high-pressure side vent valve, and a purge gas inlet valve. Internal passage of the intersection piping between components is in a "cross" pattern. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]