Near Intersection of I-35 & I-90 Southern Mn. | The single valve Fast Close NH3 is difficult to work with. Especially at low rates.
You would be much better off with a two valve system. With a two valve system one valve is the ON/OFF valve. Its purpose is to allow or not allow the flow of NH3. It is either fully open or fully closed.
The second valve is the control valve. It's purpose is to adjust the flow. It has a gear box between the motor and the ball valve that reduces the speed of the ball considerably compared to the speed of the motor. The control valve should take about 8 seconds to go from its fully open to fully closed position. This allows the system a better chance of adjusting the flow as compared to the single Fast Close valve. With the Fast valve, the system must use extremely small corrective "shots" of electricity in an effort to nudge the ball valve just slightly. This is a problem at high rates and even more of a problem at lower rates.
Commonly the control valve is a 1" Jamesbury ball valve although I've heard of situations with low flow requirements where a 3/4" ball valve was used instead to imporove control at the lower rates.
Another trick that I have used in the past is to weld the holes in the NH3 knives shut (field cultivator at 18" spacings) and drill a new much smaller hole ( 1/8" ) in the tube. This has the effect of creating more restriction right at the knife. This helps "even out" the flow between knives and also creates extra back pressure so the system has a better chance for control.
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Min NH3 rate with Raven system
