Near Intersection of I-35 & I-90 Southern Mn. | I have no experience with that combination. I would have expected the section valves to just be ordinary ON/OFF valves since I don't think they would be involved with control.
There are various type of valves dealing with NH3.
Originally there was the Standard Control Valve. It was analogous to the butterfly type valve used with sprayers. It's only purpose in life was to control the applied rate. It had a motor which is geared down considerably so that it can move the ball slightly for rate control. It takes about 8 seconds to go from minimum to maximum.
Nest inline was a "regular" ON/OFF valve. Its only purpose in life was to act as an ON/OFF valve so it is either fully open or fully closed. So in normal operation, the ON/OFF valve opens fully but the NH3 reaching it has been restricted by the Standard Control valve. When application ceases, the ON/OFF valve shuts quickly stopping product flow. The Standard Control valve stays at it present location.
This combination of having a valve for control and a separate valve for ON/OFF is still the best approach.
Later as a cost cutting move, Raven decided to use a single valve to handle both the rate adjustment and the ON/OFF function. This meant that the valve would need to go to fully closed when application ceased but open partially when application resumed. This meant that the motor could not be geared down so much since it would take too long to stop the flow. The downside to not reducing the motor speed so much is the controller then must send extremely small adjustment "shots" to the valve to move the valve very slightly. When application resumes, the system has no idea how far open the valve should be so it keeps opening it until the applied rate exceeds the target rate and then backs off. Having a standard control valve that has not moved is a much simpler approach.
This arrangement can work but has problems with low flow rates since it is difficult to move the ball just slightly without the gearing. It is more confusing to the operator also.
If I were going to setup your bar from scratch, I would have used a Standard Control Valve followed by an NH3 ON/OFF valve which would be called the Master ON/OFF valve. The flow would split and go to each of two NH3 ON/OFF valves to shut ON/OFF their respective sections. The liquid line for the heat exchanger would be teed off after the Master ON/OFF valve.
I would not use any Fast/Fast Close valves on the bar.
Edited by tedbear 3/26/2025 10:48
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Raven control module
