Selectors (multiposition valves) step incrementally through continuous revolutions, instead of switching back and forth like two position valves. (Selectors step bi-directionally with microelectric and universal actuators.) The preload design allows the rotor to be inspected or replaced without taking the valve off the actuator. Valves ordered with a microelectric actuator are permanently aligned.
Valco selectors are available in five lower pressure flowpaths typically used in gas chromatography applications (most also available with the built-in purge feature), and two high pressure flowpaths suitable for high performance liquid chromatography.