Tags: Pilot Operated

Hydraulic Pilot-Operated Check Valves

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Hydraulic Pilot-Operated Check Valves

The cylinder in the system in Figure 4.22 should, theoretically, hold position when the control valve is in its centre, off, position. In practice, the cylinder will tend to creep because of leakage in the control valve. Check valves have excellent sealage in the closed position, but a simple check valve cannot be used in …

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Hydraulic Pilot-Operated, Four-Way Valve

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Hydraulic Pilot-Operated, Four-Way Valve

This type of valve is used to control the flow direction by using a pilot pressure. Figure 5-28, shows two units in which the spool is shifted by applying the pilot pressure at either end of the spool. In the spring-offset model, the spool is held in its normal offset position by spring thrust and …

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Hydraulic Four-Way Valves

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Hydraulic Four-Way Valves

Four-way, directional-control valves are used to control the direction of fluid flow in a hydraulic circuit, which controls the direction of movement of a work cylinder or the rotation of a fluid motor. These valves are usually the sliding-spool type. A typical four-way, directional-control valve has four ports: • One pressure port is connected to …

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Hydraulic Check Valves

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Hydraulic Check Valves

Check valves are the most commonly used in fluid-powered systems. They allow flow in one direction and prevent flow in the other direction. They may be installed independently in a line, or they may be incorporated as an integral part of a sequence, counterbalance, or pressure-reducing valve. The valve element may be a sleeve, cone, …

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Hydraulic Pilot-Operated Check Valve

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Hydraulic Pilot-Operated Check Valve

The pilot-operated check valve is shown in Fig. 7.11. For flow in the forward direction, this valve operates just like a normal check valve. Pilot line pressure holds the valve open for fluid in the reverse direction. If the pilot line is pressurized (for example, if there is pressure at P0 in Fig. 7.10), the …

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Hydraulic Pilot Operated Relief Valve

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Hydraulic Pilot Operated Relief Valve

A pilot-operated relief valve has the same function as a direct-acting relief valve; however, it has a different pressure vs. flow curve. The performance curves for the two types of relief valve are given in Fig. 3.7. The pilot-operated valve opens completely over a narrow pressure range. This allows the circuit to operate over a …

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