South Georgia | JRM - 3/21/2014 22:38
(mostly with self propelled, not a whole lot with pull type) the self propelled sprayers with variable pumps hold the rate a lot better as you change speeds.
I think this is probably the biggest part of the reason. The servo valve may take a few seconds to adjust, whereas the PWM valve can adjust practically as fast as the controller sends it a new signal. It can instantly go from a 25% signal to a 75% signal, where it may take a servo valve two seconds to get from an equivalent low flow rate to an equivalent high flow rate. Think how important this may be when accelerating from low speed while exiting the headlands, when one boom section was initially on at 5 mph, but by the time all sections are on you're already travelling 8 or 10 mph. Applied flow rate may have started at something like 3 GPM and increased to a desired rate of 30 GPM in the course of a few seconds. PWM can come a lot closer to meeting that changing flow rate on time.
Also, it's two less components to build into the sprayer. A hydraulic drive pump is going to have a flow control valve regardless, so it may as well be a PWM valve rather than a manual flow adjusting valve plus a solenoid valve to turn the pump off with. The PWM valve takes the place of both of these, plus eliminates the servo valve.
Adrian |
why don't rogators have an automatic controlled throttling valve?
