The Metering Pump
T
he metering pump is a positive displacement chemical
dosing device with the ability to vary capacity manually or automatically as process conditions require. It features a high level of repetitive accuracy and is capable of pump-
ing a wide range of chemicals including acids, bases, corrosives or viscous liquids and slurries.The
pumping action is developed by a reciprocating piston which is either in direct contact with the process fluid, or is shielded from the fluid by a
industrial diaphragm. Diaphragms are actuated by hydraulic fluid between the piston and the diaphragm.
Metering pumps are generally used in applications where one or more of the following conditions exist. • Low flow rates in ml/hr or GPHare required• High system pressure exists • High accuracy feed rate isdemanded• Dosing is controlled by computer,microprocessor, DCS, PLC, orflow proportioning• Corrosive, hazardous, or hightemperature fluids are handled• Viscous fluids or slurries need tobe pumped
Metering Pump Basic Components
Driver:
The pump is usually driven by an AC constant speed motor. Variable speed, pneumatic, and hydraulic drivers are also utilized.
Driver Mechanism:
The drive mechanism translates the rotary motion of the driver into reciprocating movement.
Industrial duty pumps will
submerge this portion of the pump in an oil bath to assure reliability during continuous operation.
Flow Adjustment:
Pump flow rate is adjustable by varying stroke length, effective stroke length, or stroking speed.
Most metering pumps are
supplied with
a
micrometer screw adjustment similar to the one shown here. The micrometer can also be replaced by an elec-
tronic or
pneumatic actuator to adjust pump flow rate in response to process signal.
Liquid End:
The liquid end design and materi-als of construction are determined by the service conditions, and the nature of the fluid to be
handled.
Temperature, flow rate, fluid viscosity, cor-
rosiveness and other factors are considered.
Drive Mechanism Liquid End
Driver FlowAdjustment 1