without and with leakage port
Poppet valve without overpressure function
max. operating pressure 500 bar
Pressure reducing valves maintain the pressure at the cylinder port A (secondary pressure) more or less constant at a variable but always higher input pressure P (primary pressure).
Below the adjusted secondary pressure the hydraulic oil flows without any impediments from P to A. In case of pressure increase to the desired closing pressure a hermetically sealed pressure reducing valve shuts off the oil flow. Thereby a further pressure increase is avoided, also in case of further increasing primary pressure P.
In case of a pressure drop, e.g. because of a leakage at a cylinder, the check valve will be opened by a strong spring against the existing primary pressure. Hydraulic oil can continue flowing until the adjusted secondary pressure is obtained.
Increasing secondary pressure, e.g. due to temperature rise cannot be compensated, since there is no leakage oil port.
This pressure reducing valve is especially suitable for clamping systems which will be uncoupled from the pressure generator, e.g. pallets, because an additional leakage oil line is not available.
Limits of application
The pressure reducing valve can only be used in static clamping systems. The connected clamping elements must be leakage-free.Due to the missing leakage oil port an increasing pressure cannot be compensated at the secondary side. Pressure increase is possible because of temperature increase, external forces or damage of the valve seat by swarf.
Recommendation: Installation of an additional pressure relief valve at the secondary side as a safety measure against pressure increase.
The opening pressure should be adjusted approx. 10 % above the secondary pressure, however, should not exceed the admissible operating pressure of the connected elements. The secondary pressure can be adjusted and controlled by means of a pressure gauge. By this way the required sealing of the system is controlled too. The sequence shown in the application below should be considered if flow control valves and sequence valves are connected in series.
Poppet valve with overpressure function
max. operating pressure 500 bar
In hydraulic clamping systems, it is often necessary to pressurise single clamping elements or groups of clamping elements with reduced pressure.
This version with overpressure function compensates not only a pressure drop, but also a pressure increase above the preset pressure. For this purpose, a separate line to the reservoir must be provided. Possible causes for a pressure increase are:
• Temperature increase (approx. 10 bar per 1°C)
• Force increase acts on the clamping cylinder
• Damage of the valve seat by swarf
Below the set outlet pressure, the hydraulic oil flows unhindered from P to A. In case of a pressure increase, the set spring force is overcome and a check valve cuts off the flow hermetically sealed. Thus, a further pressure increase is avoided, also in case of increasing inlet pressure p. In case of a pressure drop, e.g. because of a leakage at a cylinder, the check valve will be opened by a strong spring against the existing inlet pressure p. Hydraulic oil can continue flowing until the set outlet pressure is obtained.
If the outlet pressure increases, e.g. because of oil warming, a pressure relief valve opens. Thus, oil in the outlet pressure area can drain off by the reservoir line until the preset outlet pressure is more or less obtained and the pressure relief valve is closed. A return flow from A to P is only possible if the inlet pressure p drops below the set outlet pressure.
The pressure reducing valve C2.9533 is available as screw-in valve, for pipe thread or manifold-mounting connection.