Advancement in multiple-channel direct injection into a spray nozzle using a stepper motor to actuate a series of task-designed pumps

A direct nozzle chemical injection system was designed to inject various amounts of chemical directly at-the-nozzle. The system included four task-designed diaphragm pumps with different diaphragm diameters. Diaphragm diameters were 5/8, 3/4,1-1/4, and 1-1/2 inch. A removable valve body provided a means for quick access to the check valves for maintenance. The valve body served as an inlet port for chemical formulation into the pump, as well as a supply channel from the pump chamber to the diluent line. Each pump included a sandwich diaphragm constructed from Teflon and Viton to increase the life of the diaphragm for chemical resistance and durability.

A screw-actuated linear stepper motor (Servo Systems M31-34A-9106D) was incorporated as a driver. The stepper motor provided accurate control over the stroke length, and provided variable speed control of the pumps. System design utilized a clamping feature and a common diluent supply allowing for a single pump to be assembled with the nozzle body, or a series of multiple pumps with a nozzle body driven by a single motor.

The 3/4-inch diaphragm pump was evaluated. During testing, problems arose in controlling the flow of water through the pump. Water was used to simulate the chemical liquid. Water was visibly moving through the pump chamber without the aid of the pump. Corrections to the inlet pressure head were established and the system was primed. Initially the 3/4-inch diaphragm pump produced flow against zero back pressure. However as back pressure was introduced, the pump failed to provide flow.

Further attempts were made to produce flow. Each attempt narrowed the problem to the check valves. The check valves were externally housed in clear Teflon tubing in order to isolate the problem with the valves. During pump operation, the exiting check valves Med to restrain the back pressure flow. The pump chamber was unable to pressurize and produce flow against a back pressure because the check valves allowed an average of 0.0031 gal/min to leak into the pump chamber from the dilute line.