The figure above illustrated the working principle of direct acting relief valve. When the hydraulic force Fh equals spring force Fs, the valve cracks open, meaning that the spool lifts off its seat and allows fluid to flow to the reservoir. As pressure increases, the spool lifts higher, allowing more flow to bypass to the …
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A counterbalance valve opens a free flow in one direction while regulating the opposite flow until a certain pressure is reached. Counterbalance valve typically installed in line between directional control valve and a vertically mounted hydraulic cylinder actuator. Counterbalance valve act as a hydraulic restrictor to hydraulic cylinder. For example, a counterbalance valve is used …
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A poppet valve consists of movable poppet which closes against a valve seat. The inlet pressure will hold the valve on closed position. The poppet will open if the poppet stem is applied by a small force. The poppet stem is equipped with an O-ring to prevent oil leakage. The number of poppet in a …
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In an open-center sliding spool directional control valve, the spool is designed to pass all flows on all its passages when the valve is centered. In some types, the fluid from hydraulic pump is passed to the reservoir through other side of the valve while the cylinder port is blocked. To keep the directional control …
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In a closed-center sliding spool directional control valve, all the flow passages are blocked when the piston is centered in its body. The closed-center valve is applied if a single hydraulic source (pump/accumulator) performs multiple operation and the system is not tolerated any pressure loss during stroke shifting. The figure above shows closed-center sliding spool …
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Manually operated directional control valve is used to control the flow direction by manual hand force. The spool can be shifted by applying force at the hand lever. If the valve is a spring offset model, the spring thrust will hold the spool in the out position and spool can be shifted in the in …
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Hydraulic pilot operated four-way valve is used to control the hydraulic fluid flow direction by using a pilot pressure. In the figure above, if the pilot pressure on either spool side is pressurized by a hydraulic fluid pressure then the spool will be shifted. If the unit is a spring offset type, the spring trust …
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Solenoid operated directional control valves are used to control the hydraulic fluid flow direction electrically. A spool fitted inside valve body will shift if the solenoid which located at both ends of spool is energized. In one side of solenoid is activated, the rod will be pushed against the end of spool. The spool will …
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Hydraulic flow divider valve is used to synchronize two actuating unit. A flow divider divides a single flow stream into two equal streams so each actuator receives the same flow rate. The figure above showed a flow divider valve in the splitting position. The fluid will enter through port 3; the pressure in port 3 …
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Orifice Check Valve is used on a fluid system which needs normal operation speed on one direction and reduced speed in other direction. The figure above shows orifice check valves schematic.
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