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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.
Peristaltic Metering Pumps
Peristaltic metering pumps, like diaphragm metering pumps, are positive displacement pumps. However, they operate quite differently. Peristaltic pumps use rotating rollers to squeeze a flexible tube to move the liquid in a pressurized flow. As the tube is constricted and the low-pressure volume increases, it creates a vacuum that pulls the liquid into the tube. The liquid is then pushed through the tubing as the tubing is constricted at several points by the rollers. With each oscillating or rotating motion, the fluid flows through the tubing. Peristaltic metering pumps are designed as either circular (rotary) or linear.
Benefits of Metering Pumps
Metering pumps, whether diaphragm or peristaltic, provide many benefits to the industries where they are used. They are reliable for dispersing the exact amount of liquid that is needed accurately and consistently. Additionally, you will find the following advantages when using metering pumps:
They commonly move low amounts of liquid – Because metering pumps are so accurate and precise, they are often used to move low amounts of fluid. They are typically measured by their capability to pump gallons per minute, instead of gallons per hour, which is an industry standard.
They can pump various types of liquid – Metering pumps are able to move a variety of fluids, from thin to thick, and even hazardous or corrosive chemicals.
They can be used for many different applications – Metering pumps are used in many different industries including medicine, food processing, agriculture, and manufacturing.
They prevent contamination – Both diaphragm and peristaltic metering pumps are effective in preventing the media being pumped from contaminating the pump and the workspace.
While metering pumps work effectively for many applications and different liquids, it isn’t recommended that they be used for moving most types of gases.
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