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Hydraulic Sequence Valve Operation

The sequence valve is used to ensure that a certain pressure level is achieved in one branch of the circuit before a second branch is activated. Consider a machining operation where the workpiece must be clamped with a certain force … Continue reading

25. December 2009 by and
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Differential Unloading Valve Basic Operation and Symbol

There is a type of unloading valve identified as a differential unloading valve. This valve is designed to allow the accumulator to partially discharge before the valve is unvented. Generally, the valve is designed to unvent when the pressure drops … Continue reading

25. December 2009 by and
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Hydraulic Unloading Valve Circuit Operation

In the circuit in Fig. 3.15, the pump builds pressure in the accumulator until the setting of the unloading valve is reached. At this point, the unloading valve opens, and flow bypasses to the reservoir. The pressurized fluid is trapped … Continue reading

24. December 2009 by and
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Hydraulics Unloading Valve Basic Principle and Symbol

The symbol for an unloading valve is similar to the symbol for a relief valve except that the pilot line is not connected to sense pressure at the valve inlet. The two symbols are compared in Fig. 3.14. A circuit … Continue reading

24. December 2009 by and
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Pilot-Operated Relief Valves Hydraulic Circuits

A pilot-operated relief valve can be used to unload the pump at low pressure during periods between work cycles. The schematic in Fig. 3.10 shows a solenoid-actuated directional control valve connected to the remote pilot port on the side of … Continue reading

23. December 2009 by and
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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 … Continue reading

23. December 2009 by and
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Hydraulic Direct Acting Relief Valve

A schematic of a direct-acting relief valve is shown in Fig. 3.4. Pressure acts on the annular area of the valve spool. The hydraulic force is given by The notation Fs will be used for the spring force. When Fh … Continue reading

23. December 2009 by and
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Directional Control Valves Symbols

ANSI symbols are introduced here as they are needed. The directional control valve symbol is the most intuitive and selfexplanatory of the symbols. Some experience with the directional control valve symbol has already been gained. At this point, it is … Continue reading

23. December 2009 by and
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Hydraulic Pressure Control Valves

Pressure control is a key element in the design of any circuit. Not only is it the key to achieving a given functional objective, it is also the key to safe operation. Components are designed to operate at a given … Continue reading

23. December 2009 by and
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