Near Intersection of I-35 & I-90 Southern Mn. | I agree with Ron's comments. If you wish to be certain that the flow to the ground at times is zero, then an ON/OFF valve may be the answer.
In some of these situations we have used a three-way valve that operates as an ON/OFF valve. A 3-way valve is the type that has one inlet and two outlets to direct the flow to the right port or the left port. When power is applied to the trigger wire the valve directs all the flow one direction. When power is not applied to the trigger wire the valve directs the flow to the other port. This valve can be plumbed into the system so that when it is OFF, any flow is directed back to the tank preventing any from getting to the ground.
We have some customers who are doing this with a ground driven pump for selective application of SoyGreen in soybean fields. They feel that the product is needed in some areas but not others. Using a 3-way valve allows them to turn the SoyGreen ON/OFF at will.
We have another customer who wanted to automate this process as he was afraid he would forget to run the switch properly. Since he had Ag Leader Direct command liquid components availabe from a sprayer he put these on the planter. He plans on creating an Rx map of the areas where he wants the SoyGreen.
He will have two rates on his Rx map, 5 gal/acre and 0 gal/acre. There is no control valve in his system as the stroke of his pump is set for 5 gal/acre. When the system sees a target rate of 0 gal/acre, the ON/OFF valve (3-way) will direct all output from the pump back to the tank. When the system sees a target rate of 5 gal/acre the ON/OFF valve will open and direct all output from the pump to the ground.
If the applied rate is not 5 gal/acre, the system will attempt to run a control valve but this will have no effect as there is no control valve connected.
If the observed rate is consistently different from the target rate, the operator could change the target rate or the stroke setting on the pump if it is in fact incorrect. Increasing the % tolerance can prevent nuisance alarm warnings.
Edited by tedbear 4/26/2011 06:58
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