These valves are pressure control valves directly operated with hydraulic buffer, which can

be actuated by internal or external or external pilot pressure. The valves with an integral

check valve are also available. These valves can be used in such a case where free reverse

flow from the secondary port to primary port is required. There are various type of valves

available inchuding sequence, counterbalance, unloading and low pressure relief valves, all

of which are operated by a pressure rise in the circuit being sensed either interally or

remotely. (Please refer to Graphic Symblo)