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Selecting the Right Pump

Because the pump is literally the “heart of the liquidsystem”on a sprayer, careful consideration must be made in selecting the right pump.Seldom is there only one pump that will do the job.To make a wise choice, you will need to know about pump types, how the pump is to be driven and the flow and pressure requirements for your specific spraying system and application.To ensure you can closely match the pump to yourneeds, Hypro manufactures six types of pumps:roller, centrifugal, transfer, diaphragm, turbine and piston pumps.

Centrifugal and Transfer Pumps (non-positivedisplacement)

In centrifugal pumps, spray solution enters through thecenter of a rotating impeller that’s driven at speeds up to 6000 RPM.Spray solution is forced to the outer edge of the housing.This centrifugal force is what delivers the liquid to the nozzle.Traditionally thought of as low to medium pressure pumps, Hypro’s centrifugal pumps can deliver from 0-190 psi and flow rates up to 370 gpm. Because centrifugals have minimum surfaces to wear and no valves, they are very durable, easy to maintain and well suited for pumping abrasive and corrosive materials.Because centrifugal pumps operate at higher speeds, thePTO speed must be increased through a speedup gear drive, belt/pulley drive, gas engine drive, or a high-speed hydraulic motor.(Hypro has models specifically designed for each of these applications).The broad, versatile line includes models with ruggedhousings of cast iron, polypropylene and stainless steel that stand up to the wide variety of agricultural chemicals.

“Positive displacement”vs.“Non-positive displacement”

Hypro’s long line of pumps can be divided into two general categories:“positive displacement”and “non- positive displacement.”Roller, diaphragm and piston pumps are positive displacement.That is, the flow from the pump is directly proportional to the pump speed.This positive flow is why all positive displacement pump hook- ups must include a relief valve and bypass line between the pump outlet and the nozzle shut-off valve.Centrifugal and turbine pumps are non-positivedisplacement.In these pumps, a rotating impeller creates a centrifugal force that feeds the liquid through the system instead of capturing and discharging a fixed volume “per stroke”as rollers, pistons or diaphragms would do.Therefore, if the outlet is closed, the impeller simply continues to rotate harmlessly.That is why special relief valves are not required in centrifugal pump systems. 2