Hydraulic power pack components pdf

This article is about power machinery. Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium. In normal cases, hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and trackdrives for an excavator. Cylinder C1 is one inch in radius, and cylinder Hydraulic power pack components pdf is ten inches in radius.

The downside to this is that you have to move C1 a hundred inches to move C2 one inch. 10 times less than the pump shaft speed. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid’s pressure will rise to meet any resistance, since the pump has a constant output. This type of circuit can use inexpensive, constant displacement pumps. The pumps vary their flow rate, pumping very little hydraulic fluid until the operator actuates a valve. The valve’s spool therefore doesn’t need an open center return path to tank.

Multiple valves can be connected in a parallel arrangement and system pressure is equal for all valves. Pump pressure always equals the pressure setting for the pump regulator. This setting must cover the maximum required load pressure. Pump delivers flow according to required sum of flow to the consumers. The CP-system generates large power losses if the machine works with large variations in load pressure and the average system pressure is much lower than the pressure setting for the pump regulator. CP is simple in design.

Works like a pneumatic system. New hydraulic functions can easily be added and the system is quick in response. Same basic configuration as ‘standard’ CP-system but the pump is unloaded to a low stand-by pressure when all valves are in neutral position. Not so fast response as standard CP but pump lifetime is prolonged.

CP-system with respect to system stability. The LS-system also requires additional logical valves and compensator valves in the directional valves, thus it is technically more complex and more expensive than the CP-system. If the pump flow is high the extra loss can be considerable. The power loss also increases if the load pressures vary a lot. The cylinder areas, motor displacements and mechanical torque arms must be designed to match load pressure in order to bring down the power losses. Load sensing with synchronized, both electric controlled pump displacement and electric controlled valve flow area for faster response, increased stability and fewer system losses. This is a new type of LS-system, not yet fully developed.