Irrigation pumps are used to pump water from a lower to a higher level from which the water then flows through channels to the fields requiring irrigation (lift operation) or to raise it to the required pressure head so that it can be sprayed on the fields via piping systems (sprinkling).
The benefits or advantages of irrigation pumps are:
Water Conservation – Over pressurized sprinklers tend to “fog” or mist as the higher pressure creates smaller water droplets through the sprinkler’s nozzle.
Several Pumps In One – With a VFD now one of the larger pumps can serve as the jockey or PM pump to provide water to the system when the pressure and flow rate requirements are, but it can also step up and deliver higher flows and higher pressure when the system demand dictates.
Irrigation System Flexibility – This means a smaller zone can be run and the system will slow the pump down thus reducing the flow and pressure to deliver exactly what is needed to operate the smaller zone. The Variable Frequency Drive (VFD) allows the pump to be run at a lower speed thus reducing the pump’s performance. In the past the solution to this problem is to size the pump for the worst possible case and then try to come up with some combination of valves to get the pump to operate at the best efficiency point. Agricultural irrigation systems are typically zoned by field size, crop type and/or crop maturation date.
A centrifugal pump must be put under water, or primed, before it will move water. A combination of the speed of the vapour bubbles and the implosion of vapour bubbles can be corrosive to the impeller surfaces and pump casing. As long as the liquids aren’t too viscous, like mud or waste, and the pump can be totally submerged, it will provide consistent, effective, and reliable operation.
Centrifugal pumps provide a lot of flexibility, are easy to move, and don’t take up a lot of space. For most household or light industrial uses, a centrifugal pump is fine. The main disadvantage is that they use rotation instead of suction to move water, and therefore have almost no suction power.
Centrifugal pumps can also develop a phenomenon called “cavitation”. This happens when the speed of the water causes it to vaporise, which causes bubbles in the liquid.