Hydraulic Sequence Valve Operation

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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 before it is extended to make contact with the cutting tool. If the piece is …

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Differential Unloading Valve Basic Operation and Symbol

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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 15%. Differential unloading valves are also available that unvent when pressure drops 30%. Unventing means …

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Hydraulic Unloading Valve Circuit Operation

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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 in the accumulator by the check valve and the closed-center directional control valve. A functional …

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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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Directional Control Valves Symbols

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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 necessary to review the three most common center configurations (Fig. 3.1) for spool-type directional control …

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Hydraulic Pressure Control Valves

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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 maximum pressure and will withstand pressure peaks up to some burst pressure. Failure of a …

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