Posted 3/25/2020 17:51 (#8138322 - in reply to #8138188) Subject: RE: Raven 440 to Hardi Ranger 2200
Southern Minnesota Between Freeborn & Wells
I had forgotten that Raven had a calibrated reflow on one of their controllers for this purpose. I assume they all work under the same principle. The assumption is that the amount going back to the tank when a boom is off is the same as if the boom were on and the product was getting to the ground. The system then just factors the flow volume accordingly.
A simple example: The sprayer is 60' with three 20' booms. Each boom valve either directs the spray to the ground or back to the tank. The back pressure or resistance back to the tank is the same as the boom. The flow meter is ahead of all boom valves so it measures the total flow at all times. With all booms ON, all the flow gets to the ground and total flow is correct.
If one valve is OFF and the other two are ON, the assumption is that the flow going back is the same as if it were ON so the system uses 2/3 of the flow for its computations for total volume. It uses this value for the rate also but the effective width is also 2/3 so the rate works out correctly. With only one section ON, the assumption is that 2/3 of the flow is being returned so the flow volume used is 1/3.
The difficulty of using this calibrated reflow is the back pressure orifice or restriction. If the spray tips are changed to a different size, the orifice or restriction needs to be changed also so as to maintain the same back pressure when the section is off.
My example used 20' for each section. The situation of finding the proper orifices for the return path is more confusing with unequal sections since the restriction would need to be different for different width sections. This can be very confusing.