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DE | why don't they have a 12volt auto adjusting throttling valve after the flow meter like I have on my 750 ag chem pull type. My understading is the rogator automatically adjusts pump speed to maintain set gpa but why is that better than the auto adjusting throttling valve like on my sprayer? thanks. |
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MN | You get a lot more variability in flow rates with that type of system. With a fixed displacement pump (like on your 750), you are always pumping "X" GPM. If you want to spray less than that, you have to bypass whatever fluid you don't want out of the booms. Too much bypass and you can run into problems (foaming for one). If you want to spray more than "X" GPM, well, you can't.
With a variable pump (old Rogators were often hydraulic servo control, new are hydraulic PWM control), you can run (basically) as low of flow rate that you want as long as it is high enough to create enough back pressure to get consistent flow (small tips or a low rate kit that pushes all flow through a 1" hose prior to going to the booms) and as high as they system is designed to flow.
This gives you the ability to run many different rates, at many different speeds, at many different pressures. In my experience (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. |
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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 |
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Belwood, Ontario | So how do you explain the hyd servo valve that he has on his 854?
The simplest reason for the above question is. The servo butterfly is better at controlling low rates, the hyd control is better at controlling higher rates, that's why rogator has the low flow option kit that plumbs in after the flow meter |
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DE | I have a pto centrifugal pump on my pull type and I can full pto rpm with booms and sparge valve shut off without any problems. Never had any foaming problems unless I let the water get below the sparge tube with it on. |
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MN | How many GPM is it even possible of producing compared to a RoGator that will spray high rates at 120' spread and high speed? Also, have you tried pushing that kind of bypass through with every herbicide, fungicide, insecticide, fertilizer, and mix that a COOP would spray? |
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South Georgia | sprayertech - 3/22/2014 06:46
So how do you explain the hyd servo valve that he has on his 854?
The simplest reason for the above question is. The servo butterfly is better at controlling low rates, the hyd control is better at controlling higher rates, that's why rogator has the low flow option kit that plumbs in after the flow meter
I don't know, I missed that when I read the previous post earlier. That would still eliminate two components, and you may well be right, that this could be better at controlling higher flow rates. However I'd be amazed if anybody now is using pump speed control to control flow rates but not using PWM instead of servo hydraulic control, because of the other benefits I listed.
Adrian |
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Belwood, Ontario | Rg 700 has an option for butterfly control and constant speed pump |
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why don't rogators have an automatic controlled throttling valve?
