Common Uses For Metering Pumps

How Metering Pumps Work and Some of Their Common Uses

Most people will be fairly familiar with the day-to-day use of pumping equipment. It is used to supply the water to our homes and offices and, in the case of high-rise buildings, additional units are used to ensure that the water pressure is sufficient even for those housed on the top floor. On a commercial scale, it is used to carry crude oil from wells to distant refineries, while the chemical industry makes widespread use of such equipment to perform their various processes. However, somewhat less widely recognised is the role played by metering pumps which, nevertheless, are important to several aspects of our daily lives.

As their name implies, the action of these devices is not just the transport of fluids along a pipeline, but also the measurement of the fluid transported. More precisely, they are designed to deliver a precise quantity of a fluid within a given period of time. While they can be used to transport water, it is for the delivery of precise quantities of various chemical solutions that metering pumps are most often required. So, how do they work? Also known as a dosing or proportioning pump, the device is designed to draw liquid into a chamber with a known volume and, once filled, discharge the pre-measured contents of that chamber, usually into a tank or a pipeline that contains the fluid that needs to be “dosed”. The units are powered by an electric motor or compressed air and the flow rate of these metering pumps is managed by an automatic controller. These devices can take various forms, the most common of which rely on the principle of positive displacement and employ a mechanically, electromagnetically, or hydraulically operated diaphragm. The extent to which the diaphragm is displaced will determine the volume of liquid that is drawn and subsequently expelled with each stroke when using this type of device. Peristaltic, rotary-vane, plunger, and piston-operated metering pumps are among the alternatives

A common example of the dosing process in action is one from which most of us benefit, although probably without being aware of the details. The process involves the addition of precisely measured amounts of chlorine or chlorine compounds to our drinking water to ensure it remains sterile throughout its journey to the taps of consumers. This form of dosing is routinely undertaken at municipal water-treatment plants where a similar technique is often used to improve the separation of fine solids under gravity. In this case, the metering pumps are used to add measured amounts of chemical coagulants or flocculants which cause the finer, suspended solids to form dense aggregates. In addition, because most of the water treatments work best at a pH of 7, these units are also used to add the quantities of acid or alkali required to achieve neutrality.

Many industries rely on the use of boilers to perform various tasks and, to ensure that they continue to function efficiently and remain serviceable, they must be kept free of limescale. This is best achieved by adding suitable anti-scaling agents to the process water. Once again, the solution is to employ a metering pump to ensure adding the required amount for the volume of water to be treated. Anti-corrosion agents are often introduced into a system in this fashion to protect steam turbines and other machinery that might be at risk. Although it may not be a business that most people would immediately associate with pumping equipment, one of the biggest users of dosing technology is the processed-food industry. What better way for a manufacturer to ensure that your favourite brand of tomato sauce or pureed fruit dessert contains precisely the right blend of ingredients than to delegate control of the proportioning process to metering pumps?

When selecting the right equipment for a given dosing task, there are a number of criteria that must be considered. These include the flow rate, which can range from just a few millilitres per hour to more than 70 ℓ per minute, the total head or pressure, which might be anything from 10 to 30 000 psi, and the horsepower. For expert help with that decision, the guarantee of a world-class product and impeccable after-sales service, many of South Africa’s leading users of pumping equipment choose to rely on Prochem Chemical Pump Manufacturers to supply, install, and support their metering pumps.

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