Near Intersection of I-35 & I-90 Southern Mn. | The "Standard" control valve should work much better at the lower flow rates since there is a gear down transmission between the motor and ball valve. This means that to go from fully closed to fully open means the valve will take about 8 seconds. Since the standard control valve is only for control and is followed by a much quicker ON/OFF valve this works fine. When the operator shuts off the Master, the control valve stays at its current location and the ON/OFF valve goes from fully open to fully closed. When application resumes, the ON/OFF valve goes from fully closed to fully open. Because the control valve has not moved, it will be in the approximate correct position from the pervious pass.
To cheapen up the system, a single Fast Close valve can be used instead of a Standard control valve and separate ON/OFF valve This valve must serve both purposes of ON/OFF as well as rate control. That means it needs to be able to shut quickly to stop application yet, move slowly for rate control. When application resumes, the system must progressively open the control valve until the target rate is exceeded and then back off a bit. This may be fine at reasonably high flow rates. At lower flow rates, a very small change in the position of the ball will change the flow rate more so due to the ball being more toward the closed position. A split second change from the motor creates a more dramatic change in the output.
This is why the Standard valve can work better. Because of the transmission, the motor can run for a bit to create a small change in the position of the ball.
I believe a 3/4" standard control valve even exists. I think I remember of a special situation where a customer used one of them rather than the usual 1" standard control valve for a special situation with very low flow rates.
Another trick I personally used with a field cultivator was to weld the original knife holes shut and drill a 1/8" hole in the tubes. These were on 18" spacing. By reducing the size of the holes, the knives created more back pressure which made the system more stable. My Dad was afraid they would plug up but they didn't since the pressure was actually higher.
Edited by tedbear 8/9/2022 06:56
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Raven nh3 valve conversion
