Chemigation

The most popular types of positive displacement pumps

used in chemigation are diaphragm pumps and piston

pumps. Diaphragm pumps consist of a flexible diaphragm

that is oscillated by a rotating device behind the diaphragm.

Check valves on the inlet and outlet side of the pump work

together with the diaphragm to inject chemical into the

irrigation system. The advantages of diaphragm pumps

include minimal contact of chemical with moving parts

and the ability to adjust the injection rate while the pump

is operating. Piston pumps draw chemical into a cylinder

and utilize check valves on the inlet and outlet side of the

pump to inject chemical into the irrigation water. Piston

pump injection rate cannot be adjusted as the pump is

operating and piston materials are more subject to corro-

sion than diaphragm pumps. Both piston and diaphragm

pumps provide precise control of chemical injection flow

rate over a range of chemical viscosity and irrigation

mainline pressure; thus, there is very little change in injec-

tion rate with variation of chemical temperature or of the

irrigation mainline pressure. Some positive displacement

pumps are powered by irrigation water pressure; these

systems vary chemical injection rate with water flow rate

and are popular injection devices for field and greenhouse

pressurized irrigation systems.