It pays to make the right choice

Buying the wrong flowmeter can prove to be a costly mistake. James Roper of Durapipe UK presents a guide to the most appropriate - and efficient - types of application.

MONITORING FLOW is integral to the majority of water and waste treatment applications, but choosing the most appropriate product to complete the task can be a difficult process.

With the vast array of different options available on the market, it is important that specifiers and contractors consider the needs of the application carefully - all too often companies are sold over-engineered products, meaning a costly outlay for the end user.

With a view to aiding specification, Durapipe UK has put together the following guide, detailing the main types of flowmeters that are available and the ideal applications for each, to ensure that the most cost effective and efficient product is installed.

Variable area flowmeter
This is the simplest form of flowmeter and should be used when only a basic level of information is required. The flow rate is indicated by the position of the top of the float against the scale on the tube; the flow speed is displayed, but if exact levels of accuracy are required other technology may be more appropriate.

To work correctly, the flow sensor must be mounted with the flow tube axis vertical and the media flowing upwards.

A Variable Area Flowmeter is ideal for use within a system that purely needs to maintain a flow rather than measure it, such as a caustic wash that needs to be continuously circulated around a system.

Paddle wheel flowmeter
The digital paddlewheel technology provides a greater level of accuracy and calibration so that the flow can be controlled to a higher degree. The mechanical process is simple but effective; the flow of the fluid moves the wheel and this speed is converted into the flow rate.

Providing a highly accurate reading, the sensor can measure flow from 0.15m/s.
This type of flowmeter is ideal for use with clean solutions and fluids; if it is inserted into dirty water or solids, the wheel may become contaminated and will not move freely, meaning that the readings will become inaccurate before the meter completely fails.

Insertion magmeter flowmeter
The Insertion Magmeter is a highly accurate flowmeter that is suitable to measure flow rate in both metal and thermoplastic pipelines. This technology puts an electro-magnetic charge onto the particles in the solution, which measures the speed of flow.

This sensor cannot be used with ultra-pure water as it needs the ions found in contaminated substances to carry the charge so it is ideal for use in dirty solutions, slurries and solids. The product has no moving parts so cannot disrupt the flow, ensuring a precise reading is generated.

Flow monitor and transmitter
In addition to the range of flowmeters available, flow monitors and transmitters are available to convert the signal from the flowmeters into a display indication and a 4-20mA signal for long distance transmission.

Simple calibration menus allow a customised setup of all measuring parameters and the state-of-the-art electric design ensures stable signal and long-term reliability.

This product is ideal when remote access to the flowrate readings is required; this is typical in larger treatment plants that operate multiple processes and demand instant access to system performance data.

It is crucial to select the most appropriate product for specific flow monitoring applications in order to maintain an efficient yet cost effective operation. In addition, it is also important to consider the pipework system into which it is being installed, and the other equipment with which it will need to work, such as valves and batch control or chemical dosing technology.

If all of these products can be specified from a single manufacturer, end users can be confident that a fully matched system will be installed, increasing the system performance.

James Roper is industrial brand manager at Durapipe UK. T: 01543 279909

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