Category Archives for Hydraulic Valves
Simple Pressure-Relief Valve
The most widely used type of pressure control valve is the pressure-relief valve because it is found in practically every hydraulic system. Schematic diagram of simple relief valve is shown in Fig. 1.1 and three-dimensional view is shown in Fig. … Continue reading
Unloading Valves
Unloading valves are pressure-control devices that are used to dump excess fluid to the tank at little or no pressure. A common application is in high-low pump circuits where two pumps move an actuator at a high speed and low … Continue reading
Pressure-Compensated Valves
Pressure-compensated flow-control valvesovercome the difficulty causedby non-pressure-compensated valves by changing the size of the orifice in relation to the changes in the system pressure. This is accomplished through a spring-loaded compensator spool that reduces the size of the orifice when … Continue reading
Non-Pressure-Compensated Valves
Non-pressure-compensated flow-control valves are used when the system pressure is relatively constant and motoring speeds are not too critical. The operating principle behind these valves is that the flow through an orifice remains constant if the pressure drop across it … Continue reading
Pilot-Operated Unloading Valve
A pilot-operated unloading valve has less pressure override than its direct-acting counterpart.So it does not dump part of the flow prematurely. A pilot-operated unloading relief valve is the same as a pilot-operated relief valve with the addition of an unloading … Continue reading
Direct-Acting Unloading Valve
A direct-acting unloading valve consists of a spool held in the closed position by a spring. The spool blocks flow from the inlet to the tank port under normal conditions. When a high-pressure fluid from the pump enters at the … Continue reading
Pressure-Reducing Valve
The second type of valve is a pressure-reducing valve. This type of valve (which is normally open) is used to maintain reduced pressures in specified locations of hydraulic systems. It is actuated by downstream pressure and tends to close as … Continue reading
Compound Pressure Relief Valve
A pilot-operated pressure-relief valve consists of a small pilot relief valve and main relief valve as shown in Fig. 1.4. It operates in a two-stage process: 1. The pilot relief valve opens when a preset maximum pressure is reached. 2. … Continue reading
Pressure-Relief Valves
Pressure-relief valves limit the maximum pressure in a hydraulic circuit by providing an alternate path for fluid flow when the pressure reaches a preset level. All fixed-volume pump circuits require a relief valve to protect the system from excess pressure. … Continue reading
Double Acting Cylinder
This is a standard cylinder that produces reciprocating motion. It is available in single and double rod types. Fig. 10.1 shows the single rod cylinder. This cylinder is provided with a cushion mechanism, which uses a cushion sleeve to close … Continue reading