Near Intersection of I-35 & I-90 Southern Mn. | The Raven PWM valves I've seen have been BRAND valves.
The Raven 450 can work with PWM valves and in many cases is a good fit. In particular, a good fit is to use a PWM valve to control the bed or metering rolls on a granular applicator. A PWM valve to a centrifugal pump on a sprayer certainly can work (many Big time OEMs do it that way) but there can be consequences. One being the match between the size of the centrifugal pump and the application situation.
If for example, the flow rate needed for a certain rate/ground speed is fairly low (relatively speaking), it may be difficult or impossible to get the pump to output that amount. As you are likely aware a centrifugal pump produces output once the pump RPM reaches a certain speed and is somewhat linear after that. If your needed output happens to be less than the output produced when the pump starts pumping the system will have difficulties. This is part of the reason why certain RoGators have a restrictor ball valve in the output line to cause restriction to the system for lower rates.
A problem with having a PWM valve too large for the situation can be that control might be difficult. Since a larger PWM valve will have larger internal passageways, a slight change in the position of the internal valve will result in a larger change in flow. This may or may not be an issue. With these uncertainties, I would suggest not using a PWM valve but use control in the product line itself.
I have personally used and helped install many control systems using Raven controllers as well as other brands. The majority of them have contained a hydraulically driven centrifugal pump run out of an SCV on the tractor. The SCV is set to run the pump at a speed slightly above the highest flow demands of the system. The flow rate of the system is controlled by a control valve in the product line which is mostly commonly plumbed in the inline configuration after the flow meter but prior to the ON/OFF valve(s). In normal operation the butterfly is partially open to allow the proper amount of product to flow through the system to the ground. If the situation changes and the applied rate is too great, the system closes down the butterfly somewhat more to restrict the flow. The centrifugal pump is not "hurt" by this restriction. When all the section valves are shut off, no product flows, the control valve stays at its current location and the pump deadheads the flow with the exception of a branch leading to agitation. As long as there is some product flow (agitation), the pump will not be damaged due to heat.
Edited by tedbear 2/19/2017 07:29
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Pwm question
