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08.11.2022

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.







Pressure and back pressure


High pressures are no problem in metering systems as long as there is something to counter them. ProMinent hydraulic diaphragm metering pumps therefore use a hydraulic fluid to create back pressure. The benefits this brings to the diaphragms become evident very quickly.


The industries in which ProMinent’s hydraulics technology is used:




Oil/gas production (onshore/offshore)




Refineries




Chemical / petrochemical industry




Pharmaceuticals & cosmetics




Food production




Packaging industry (bottling pumps)




What you can expect


The pumps run. They do this well and for a long time. Your hydraulic control is very precise and requires only minimal maintenance. The diaphragms are durable and provide consistently accurate metering. The technology also offers a very high standard of safety: there is a pressure relief valve in the hydraulic end as protection against overload. The multi-layer diaphragms are equipped with a diaphragm rupture warning system as standard. So you can be sure that the feed chemicals cannot mix with the hydraulic oil.







Pump Guide


The choice of pumps is huge: 80 industries, 100,000 products and infinite applications. To make it easy to find your ideal metering pump, ProMinent designed the Pump Guide. In just a few clicks you will find a selection of suitable models.


Here’s how it works


First enter the pump capacity and back pressure. The Pump Guide will then show you all the metering pumps that match your criteria. You can choose between list view and detail view. The database contains all solenoid metering pumps, motor-driven metering pumps, process metering pumps and peristaltic pumps from ProMinent. They are divided into more than 30 different product ranges.


Exactly the right pump


Narrow down your search by clicking on different selection criteria. Do you have a specific industry, operating mode, medium or viscosity in mind? Or maybe you need a pump for zones at risk of explosion? The Pump Guide will take you to the pump you need in just a few clicks.


Small-scale reverse osmosis plants that can produce less than 50 m 3 /d are vital for small communities in villages located in remote areas. The design parameters of such plants involve low flow rate and high-pressure feed. For such operating conditions, reciprocating pumps are more favorable than centrifugal pumps because the efficiency of centrifugal pumps in such conditions is reduced extensively. Recently, reciprocating pumps with energy recovery are presented by several pump companies for desalination applications. The concept of energy recovery in these pumps is quite similar to that used in pressure exchangers. In these pumps, the pressurized brine is directed to the back of the pumping pistons which reduces the pumping motor required power. This work presents a numerical simulation and experimental analysis for such pumps. The numerical simulation includes a computational fluid dynamics transient analysis for the used pump. The analysis is presented using both two-dimensional and three-dimensional models. The effects of the operational and design parameters on the performance of the pump and its volumetric efficiency are investigated. The results show that increasing the valve spring stiffness increases the volumetric efficiency. It also shows that increasing the outlet pressure and piston speed reduces the volumetric efficiency. The most striking result to emerge from the data is that reducing the valve spring stiffness below a specific value results in large reduction on the volumetric efficiency. Results of high-pressure reciprocating pump’s testing at different operating conditions are evaluated. The results of the presented numerical simulation were compared with the experimental results at several operating conditions, and the deviation was less than 10%.



What is a pneumatic diaphragm pump? An air operated double diaphragm pump is a pneumatic pump that uses a patented air valve that directs compressed air between two sides of the pump, back and forth. It can operate on regular compressed air, clean dry air, nitrogen, or even natural gas.

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