Pilot Valve – A little valve which operates a bigger check valve with very little ability necessary for use; used when the technique necessitates the no-return traits of check valves For under a percentage of the cycle. Pneumatic – Operated or pressurized by air or other gases. Pneumatic Actuator http://valvesandfittings82571.articlesblogger.com/12077584/5-simple-statements-about-hydraulica-check-valve-explained