These pumps are supplied with built in reservoir and adjustable pressure relief valves specifically designed for applications where there is a "mechanical stop" at the end of the piston or actuator travel such as an engine hatch, inspection hatch or passerelle. When the hatch is closed or fully open the relief valves prevent the hydraulic system from going into overload or damaging the hatch. The built in reservoir removes the need for a separate hydraulic filler tank making the connections to the hydraulic system simple

Choosing the size or flow rate of the pump is important and is based on the size (capacity) of your cylinder or actuator. The bigger the pump the faster the open and close or extend and retract times, "Hard Open to Hard Closed" shown below as HO to HO. The pump size does not affect the thrust or power available which is similar for all sizes of pump. In these sorts of applications the cylinders or actuators are generally small. For example a 1 litre per min pump PR+10 delivers 16.66cc per sec so would give a fully open to fully closed time of 9 secs with a 150cc cylinder fitted to some passerelles, typically an engine hatch would have 2 smaller 75cc actuators which would open or close in the same time.