In brief
A metering pump delivers a precisely adjustable volume of liquid per stroke or unit of time and is used to add chemicals and additives to processes accurately.
Contents
What is Metering pump?
Metering pumps are usually reciprocating positive displacement pumps. With each stroke, a piston or diaphragm draws in a defined volume and pushes it into the line via check valves. They are used in water treatment, chemicals, food and paper production, for example to add acids, alkalis, flocculants, biocides or dyes.
Diaphragm metering pumps separate the medium completely from the drive, while piston metering pumps achieve higher pressures. In terms of drive, a distinction is made between solenoid metering pumps for small volumes and motor-driven pumps for higher capacities. The dosing rate is set via stroke length and stroke frequency and can be controlled by analogue or pulse signals. Key parameters are capacity, back pressure, metering accuracy and the materials of the dosing head, valves and seals. Peristaltic and gear pumps are also used for metering.
Inaccurate dosing is often caused by worn or dirty valves, gas bubbles in the dosing head or a fatigued diaphragm. Crystallising media clog valves. Because dosing errors directly affect product quality or water treatment, metering pumps are considered critical in many processes. Redundant pumps or spare parts held in stock secure supply there.
In practice: maintenance and procurement
Spare parts require the pump type, dosing head size and material combination from the type designation. Keeping the diaphragm, valves and seals in stock as a spare part kit shortens downtime in the dosing process.
Synonyms and abbreviations: dosing pump · diaphragm metering pump · solenoid metering pump · chemical dosing pump · proportioning pump
Frequently asked questions
How is the delivery rate of a metering pump set?
The delivery rate results from the volume per stroke and the number of strokes per unit of time. Many metering pumps allow both to be set: the stroke length mechanically or electronically, the stroke frequency via the controller or an external signal. For accurate results, the actual volume should be calibrated against the real back pressure using a measuring cylinder.
What is the difference between a solenoid and a motor-driven metering pump?
In a solenoid metering pump, an electromagnet moves the diaphragm in pulses; it is compact and suitable for small volumes. Motor-driven metering pumps drive the diaphragm or piston via an electric motor and eccentric and achieve higher capacities and pressures. The choice depends on volume, back pressure and the required controllability.
What information is needed for metering pump spare parts?
Required are the pump type and full type designation, dosing head size, materials of the dosing head, valves and seals, and the connection design. For motor-driven metering pumps, the gear ratio and motor data are also needed. The serial number helps with older series. Materials should suit the medium, especially for acids and solvents.
Why is a metering pump dosing too little?
Common causes are dirty or worn suction and discharge valves, air or gas bubbles in the dosing head, a leaking suction line, a fatigued diaphragm or excessive back pressure. Outgassing media often require automatic venting. A systematic check of the suction side and valves resolves many cases.