Near Intersection of I-35 & I-90 Southern Mn. | I would suspect that the gearbox is your problem especially if it worked fine in the past. In some situations, a PWM hydraulic control valve is desirable for setups such as this.
Since PWM involves a digital scheme, a number is associated with the PWM output. Many controllers allow you to observe what the PWM output value is. More importantly the controller can retain the previous PWM output value. That means when application is stopped, the PWM output will drop to zero thus closing the valve and stopping application.
When application resumes, the system will initially open the valve to the previous PWM output value. This value should be very close to what is needed if the ground speed and rate are the same as previously used. This means the valve can "snap" to a reasonably correct position and then the control circuit can modify it as necessary from that point.
This is in contrast to using a Fast Close Valve. With this arrangement, the system has no way of knowing the previous valve position. When application resumes, the system must open the Fast valve to start the process and then continue to open it until the applied rate exceeds the target rate and then decrease until the rate is achieved. This can result in the system "hunting up/down" to find the correct position.
Another approach would be to use a two valve system such as I prefer with NH3. With this approach a control valve and On/Off valve are used. The control valve is only used for control. The On/Off valve is only used to start/stop application. The On/Off valve stops or diverts the hydraulic flow to stop application but the control valve remains in its current position. When application resumes, the On/Off valve opens fully but the control valve is already in the correct location from before. Thus there is no need for the system to go high then low to find the correct position.
Edited by tedbear 3/20/2020 03:24
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BBI spreader rate erratic
