Category: Pressure Control Valves

Simple Pressure-Relief Valve

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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. 1.2. It is normally a closed valve whose function is to limit the pressure to […]

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Unloading Valves

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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 pressure.The circuit then shifts to a single pump providing a high pressure to perform work. […]

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Pilot-Operated Unloading Valve

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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 spool. Without the unloading spool, this valve would function just like any pilot-operated relief valve. […]

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Direct-Acting Unloading Valve

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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 external-pilot port, it exerts force against the pilot piston. (The small-diameter pilot piston allows the […]

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Pressure-Reducing Valve

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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 this pressure reaches the valve setting. Schematic diagram of pressure reducing valve is shown in […]

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Compound Pressure Relief Valve

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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. When the pilot relief valve opens, it makes the main relief valve open. The pilot-operated […]

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Pressure-Relief Valves

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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. Fixed-volume pumps must move fluid when they turn. When a pump unloads through an open-center […]

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Yuken Pressure Switches

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Yuken Pressure Switches

Pressure switches are used in hydraulic systems to make or break an electrical circuit at a preset hydraulic pressure. A sensing component made of semi-conducting materials detects the pressure. The switches are used with relays to operate solenoid valves to unload pumps or start/stop motors.

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Yuken Balancing Valves (Pressure Reducing and Relieving Valves)

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Yuken Balancing Valves (Pressure Reducing and Relieving Valves)

These valves are combination valves that have pressure reducing and counterbalancing functions developed for applications such as a hydraulic balance circuit in a vertical machining center. When the pressure reducing function is employed, the outlet pressure is maintained at the preset level for pressure reduction, regardless of the inlet pressure. If the counterbalancing function is […]

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Yuken Brake Valves

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Yuken Brake Valves

These valves smoothly stop actuators that have a large inertia force. When a directional control valve is closed, a relief valve at the outlet side releases the accumulating pressure while maintaining the circuit pressure at the preset level. At the inlet side, a check valve feeds the flow, supply of which has been blocked by […]

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