How Does a Metering Pump Work?

Metering pumps, also called dosing pumps, are pumps that are designed to dispense specific amounts of fluid and measured flow control. They use expanding and contracting chambers to move the liquids. Metering pumps also have a high level of accuracy over time and can pump a wide range of liquids including corrosives, acids, and bases, as well as slurries and viscous liquids. They are used in various industries like manufacturing, agriculture, and medicine. There are a variety of types of metering pumps that work in different ways. For the purposes of this post, we’ll look at diaphragm and peristaltic metering pumps.

How Diaphragm and Peristaltic Metering Pumps Work

Both types of metering pumps – diaphragm pumps and peristaltic – are very useful and will typically provide many years of reliable, efficient operation.

Diaphragm Metering Pumps

Diaphragm pumps are positive displacement pumps that move liquids using a reciprocating diaphragm. They are found to be very reliable because they don’t have internal parts that rub together, creating friction and leading to wear and tear. Additionally, because they don’t require seals or lubrication in the pump head, there isn’t a chance of oil vapor contamination or leakage of the media being pumped.

Simple diaphragm pumps have a diaphragm, two valves, a displacement chamber, and a driving mechanism. The diaphragm is a flexible membrane that vibrates to create suction to move fluid in and out of the pumping chamber. It is located between the side of the displacement chamber and an attached flange. The two valves are usually flapper valves or spring-loaded ball valves that are made of the same material as the diaphragm. They operate by admitting the liquid in and out of the chamber. The driving mechanism is what activates the diaphragm into operation. There are a number of different driving mechanisms that diaphragm pumps may use. The two most common are air operated and motor driven.

Air operated diaphragm metering pumps use compressed air to drive a double diaphragm (two diaphragms) alternatively. A shuttle valve alternates the air flow between the two diaphragms. The flow of the media that is being pumped is adjusted by how much air pressure is supplied to the pump.

Motor driven diaphragm metering pumps uses the rotary motion of a motor, which is converted to a reciprocating movement via a cam mechanism, to cause a displacement in the volume of the liquid, transferring it at a consistent rate.