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Bosch Rexroth Canada ı 03.10.2011 ı Revision 5.4
5 Conveyor Hydraulic Valve Configuration
5.1 Nulling of the Valve Solenoid
Nulling of the solenoids is the process required to set the minimum and maximum
Controller amperage outputs to the solenoid, for efficient operation.
“Minimum nulling” sets the controller output amperage at the minimum amperage
required to overcome the system friction. This enhances conveyor start up during
the spreading operation as the Controller starts its output at this minimum
amperage rather than zero amps.
“Maximum nulling” sets the maximum Controller output at the amperage required to
obtain the maximum hydraulic motor speed without exceeding the maximum motor
design speed.
“Forward Gain” is another factor to be considered for prompt start up. This is built
into the system to overcome an inherit hydraulic motor pulsing problem. Once the
hydraulic motor inlet oil pressure is sufficient to create motion, the motor will pulse
during start up until it receives enough oil flow for continuous motion.
As continuous motion is required for even spreading, we need to give the motor a
“boost”, thus an additional increase in the Controller output is provided for to take
the motor past the pulsing stage. Forward Gain is only temporary and it will
disappear once the conveyor is turning.
5.1.1 Minimum Nulling
Insert the programming key, select “SENSORS AND VALVES”, and select
“CONVEYOR SETUP”. The screen to the left will appear.
Using the Navigational Arrow, move the cursor down to “VALVE SETTING” and press
Enter. The screen to the left will appear.
