Near Intersection of I-35 & I-90 Southern Mn. | Short Answer: If your control valve does not have limit switches, this behavior is to be expected. If your control valve does have limit switches they have failed.
More: Rate control can be accomplished in several ways. The most basic and common method is to use a butterfly or ball type control valve in the product line. Other systems control the speed of the hydraulic spray pump.
Apparently your system controls the flow of the actual product itself. It can be plumbed either as by pass or inline control. Inline control uses the least fittings and the control valve controls the flow by allowing more or less flow to pass through it to the flowmeter and ultimately to the ground. The by pass method of control uses a Tee prior to the flow meter where the amount of excess can be controlled that is allowed to return to the spray tank. These valves can be be same type but their reactions must be opposite. For example, to reduce the flow to the ground, the by pass plumbing arrangement requires that the valve open a bit more to allow more to bypass back to the tank, while the inline control would need to close a bit to restrict the amount getting to the ground.
Older basic systems without any automatic control often used a simple electric butterfly valve where the operator pushed a spring loaded toggle switch to send +/- or -/+ voltage to the motor to cause it to run a bit to slightly open or slightly close the butterfly. The operator watched the pressure gauge and if more flow/pressure is desired, the operator would push the INC/DEC switch up to cause the motor to turn in one direction. This should cause the flow/pressure to increase to a point but then the flow/pressure would decrease. This is because the butterfly has gone "over center" and is then affecting the flow in an opposite manner. The operator realizes this and pushes the switch down to reverse the motor to return to expected control.
If the control valve would have limit switches in it, then this would not happen. If the operator continues to push the switch up to increase the flow/pressure, the shaft inside the control valve will touch a High limit switch and break the circuit preventing it from going open any further. In a similar manner, there is a Low limit switch that prevents the motor from turning the butterfly past the completely closed position.
This type of control valve with a High and a Low limit switch is required by automatic rate controllers. If you connected a good working control valve suitable for use with your Raven 440 to a loose 12VDC battery, the motor should turn and eventually stop. Reversing the leads should cause the motor to turn in the opposite direction and then eventually stop. This process of going from fully open to fully closed should take 8 seconds. This is due to the gearing between the motor and the butterfly shaft. A Raven butterfly control valve should go from completely closed to about 90% open before it stops due to the High limit switch.
I am not familiar with the 3" Banjo Control valve that you mention. If it is the type that contains limit switches something has gone wrong with the High or Low limit switch allowing the valve to continue to turn. If it is the type that does not contain limit switches, then your observation and its operation is to be expected. You will either have to "live with it" or get a different control valve that contains working limit switches.
Edited by tedbear 4/11/2025 13:11
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Raven 440 over rotating
