Near Intersection of I-35 & I-90 Southern Mn. | flyboytoo - 6/24/2018 16:16
A piston pump is positive displacement, so you can not squeeze it down to control rate without some sort of bypass valve in-line!
One solution would be to plumb the control valve in the bypass configuration. That means putting a Tee in the line prior to the flow meter. One branch of the Tee leads to the flow meter and eventually to the ground. It is important to remember that all the flow going through the flow meter must go to the ground.
The other branch of the Tee leads to a butterfly control valve with limit switches and directs the excess back to the tank or inlet of the pump. If the setup menu allows a choice between "throttling" or "bypass" control, pick bypass. Otherwise the wires leading to the control valve can be cut and swapped.
The reason being that the control valve in the bypass arrangement needs to operate in a reversed fashion compared to a throttling setup. If the controller senses that the applied rate is higher than the target rate it would close down the control valve slightly in a throttling plumbing arrangement. It would need to open the control valve slightly in the bypass arrangement to allow more of the excess to return.
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John Deere rate controller
