Metering pumps in two stages
Most metering pumps are supplied with a micrometer screw adjustment. An electronic or pneumatic actuator may be used to replace the micrometer, if the pump flow rate needs to be altered in response to a process signal. Changing the number of pump heads in use by the device is another way to increase pump flow rate. Metering pumps with two heads can double the flow capacity of a single pump device. Pumps are also available with three or more heads to maximize flow rate. Metering pumps transfer media in two stages: the intake stroke and the output stroke.
During the intake stroke, liquid is pulled into the pump cavity past the inlet check valve. During the output stroke, the inlet valve closes; the outlet valve opens, and the fluid is forced out. The flow may be varied by changing the stroke length or by adjusting the cycle frequency. Metering pumps are generally used in applications where one or more of the following conditions exist: low flow rates in mL/hr. or GPH are required; high accuracy feed is required; high system pressure; corrosive, hazardous, or high temperature media is being transported; the media has a high viscosity or is a slurry; dosing is controlled by computer, microprocessor, DCS, PLC, or flow proportioning.
2012-09-07
