The model OP51FC is a pressure compensated swing arm adjustable flow control valve. By swinging the arm thru 90 °, the flow out the CF or controlled low port can be varied within the range given in the specification.
Any remaining flow is bypassed to the EX or excess flow port. This flow can be used to power another circuit or can be returned to the tank. Once the controlled flow is set, it will remain nearly constant with variations in pressure on either the controlled or excess flow ports.
Please note, if during operation the controlled flow port is blocked, then the valve will compensate in such a manner that there will also be no flow at the EX or excess flow port. With no relief valve to protect the flow in the circuit upstream, pump failure and or component damage will occur. If this situation could occur then it is recommended to fit an extra relief valve upstream or use the model OP51FCR valve.