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Pressure Reduction Valves
Installation, Function, Usage Example

Installation

The valve is connected in series in the pressure line (between supply pump and fluid outlet).


Function

Physical procedure during pressure control:
1

With the valve seal, the pressure-reduction valve has a pressure-active area AM. In combination with the dynamic pressure of the medium pM a medium force FM develops

FMedium = AMedium · pMedium

This medium force effects a closing of the valve.

2

The medium force FM acts against a driving force FL. FL is determined by the surface of the drive piston AL and the variable pneumatic pressure pL

FAir = AAir · pAir

This piston force effects an opening of the valve.

3

In contrast to the bypass valves, here the spring force FF must be taken into account for the equilibrium of forces. Equilibrium of forces (pressure balance) is then prevalent if the following is true:

FL = FM + FF and therefore pactual = ptarget

If the working pressure increases, then FM will be greater than FL + FF. The consequence of this is that the valve closes so long until the equilibrium of forces prevails. If the working pressure decreases, then FM will be smaller than FL + FF. The consequence of this is that the valve opens so long until the equilibrium of forces prevails.
To generate a dynamic pressure, flow-reducing elements such as chokes, nozzles, tools or the like must be connected in series downstream from the valve.

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Usage Example

1

Generating working pressure at the left valve
In this example, working pressures are generated at the left inline valve. For this, first the system pressure has to be built up by increasing the control air at the bypass valve. After that a higher and then a lower working pressure is generated by increasing the control air at the left inline valve. The closing springs on the right, deactivated inline valve prevent unintentional opening. Subsequently, the control-air- and the medium pressure are reduced to the original value again.

2

Generating working pressure at the right valve
In this example, working pressures are generated at the right inline valve. For this, first the system pressure has to be built up by increasing the control air at the bypass valve. After that a higher and then a lower working pressure is generated by increasing the control air at the right inline valve. The closing springs on the left, deactivated inline valve prevent unintentional opening. Subsequently, the control-air- and the medium pressure are reduced to the original value again.

3

Generating different working pressures simultaneously
In this example, different working pressures are generated simultaneously on both inline valves. For this, first the system pressure in the system has to be built up again with the bypass valve. After that, different working pressures are generated on both valves. It is thereby clear, that several inline valves can generate very different pressures simultaneously, without affecting each other thereby. Subsequently, the control-air- and the medium pressure are reduced to the original value again.

4

Safety concept in the event of a fault
In this example the safety concept of electro-pneumatically actuated regulating valves is presented. After the working pressures have been built up on the inline valves, the control-air feed is interrupted after an incident (emergency-stop, short-circuit). Even if the pump continues to deliver, the system pressure is immediately reduced by the bypass valve and conducted into the tank. At the same time, the closing springs of the inline valves interrupt all medium flows to the tools. Due to this two-fold security a high degree of safety is guaranteed for operating personnel and aggregates.

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Accessory – Two Pressure Regulation

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Accessory – Transmitter of Set Point Value

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