In normal operation, the pressure limit is set analog. Below the pressure limit, the pressure limiter operates as a normal proportional amplifier for hydraulic axles Accordingly, the setpoint are read in by setpoint devices or higher-level controls or sensors, and converted to proportional currents for driving the solenoids of pumps. 

When pressure limitation is activated, the volume and thus the pressure are limited according to the pressure setpoint, when the actual pressure value exceeds the pressure set value.

The DPL can also be operated as a pressure regulator. In this operating mode, the volume is set as limitation and the pressure setpoint is varied analog. Below the limiting volume, the DPL then works as a pressure regulator.

The standard ECU for the pressure limiter is the HCB controller. 2 pumps can be controlled bidirectionally. If the DPL is to be integrated into a machine controller, it can easily be ported to another Völkel hardware platform.

A special feature of the pressure regulator mode of operation is that only the high pressure A is measured. A control technology has been implemented which allows a pump to be controlled through zero in the opposite direction when back pressure induced by the hydraulic motor. The controller is therefore particularly suitable for winches in shipping, where the rope must always be kept in tension even in swell or currents (mooring system). An additional frequency input for each axle makes it possible to detect and compensate variable engine speed in order to maintain the desired volume flow. The pump swash plate angle can be measured and controlled if the pump has to be driven very precisely through zero, if the volume flow has to be controlled very precisely or small setpoint changes have to be followed precisely and quickly.

In normal operation, the DPL is used, among others, in drilling rigs where, for example, the pressure on the drill bit is to be limited. It is used as a pressure regulator in anchor winches, for mooring control, etc.

Inputs and outputs

• Digital inputs can be parameterizable as required by the application to enable various functions, ramp selection, set parameter switching, fixed values for volume, fixed values for pressure, reversal of direction, etc.
• Frequency inputs for the detection of the actual diesel engine rotary speed per axle
• Analog inputs for the analog volume and pressure set value and the actual pressure value per axle
• Proportional outputs with current feedback measurement for 2 pumps forward/reverse
• „Limitation active” output status