STRUCTURE AND FUNCTION HYDRAULIC PUMP Operation when acting as suction safety valve 1) When HST pump delivery is 0 . The HST circuit is closed, and the charge oil does not flow into the HST circuit. Therefore the charge pressurized oil from the charge pump (1) all passes the charge safety valve (2) and is drained to the pump case. Travel motor Travel pump 2 3 PB PA RKS00121 1 3 10-23 SK818-5 SK820-5 turbo