Measuring industrial water use: Meter matters

For companies to identify their water footprint and find ways to improve it requires a detailed understanding of their consumption. There are various ways to do this. One way is to deploy flowmeters to monitor individual processes and to measure and compare the difference between the incoming supply and the quantities discharged.

This information can be used in several ways. Where water is abstracted, for example, an accurate measurement will ensure that companies are within their prescribed limits and are being correctly charged for the water they use. Any discrepancy in the water balance may point to leaks, which can then be pinpointed and addressed.

Water metering can also play a key role in improving steam system efficiency. Measuring boiler feedwater and comparing it against the steam output of the boiler can help in assessing overall steam raising efficiency, which can then be used as the starting point for optimisation.

In addition, companies may use water meters to quantify waste water flows either for legislative purposes or for targeting wastage, which can also help to minimise water treatment costs.

As the data collected on water consumption will be the starting point for any efficiency improvements, it is important to use flowmeters offering the best long-term accuracy, repeatability and reliability. With space often at a premium, it is necessary to consider both the size of the meter and any requirements relating to pipe lengths and mounting arrangements. 

Finding a solution

With moving parts subject to wear and tear, mechanical meters can quickly suffer reduced accuracy, leading to under or over-registration of flows. The need for mechanical meters to be periodically tested, recalibrated and repaired also means they have to be removed, with the meter either being replaced with a temporary device or measurement being stopped until the meter is re-installed.

Ultrasonic flowmeters also suffer drawbacks. Transit time meters especially can struggle to handle flows with high levels of particulate matter, requiring a strainer to be fitted. Both transit time and Doppler meters can be affected by velocity profile distortions, requiring clear pipe runs of 10 to 40 upstream diameters, depending on the severity of the disturbance. The turndown of ultrasonic meters is also limited, within an ideal range of 20:1 to 40:1. They can be difficult to install and set up, especially where high accuracy is required.

Electromagnetic flowmeters offer enhanced accuracy and repeatability throughout their operational life, with uncertainty of ±1% reading or better. With no moving parts, they require minimal maintenance, and need no upstream strainers to filter sediment. A choice of flow primary linings, including ceramic options for abrasive flows, offers added protection against coating and high sediment flows.

These benefits are being augmented by ongoing developments in technology, both at sensor and transmitter level. 

ABB’s WaterMaster electromagnetic flowmeter, for example, features an octagonal bore sensor design that reduces its sensitivity to flow profile disturbances. The octagonal shape conditions the flow profile by flattening any distortions either upstream or downstream of the meter, enabling excellent in-situ performance even in non-ideal installation conditions. By minimising the upstream and downstream pipe lengths required from the point of installation, the octagonal sensor reduces the cost of fitting the meters into new pipelines.

Within the transmitter, the effects of signal noise are minimised by Digital Signal Processing technology which separates the real signal from application noise to provide high quality outputs, especially in harsh environments.

An added incentive to opt for electromagnetic flowmeters is the Government’s Water Technology List (WTL), scheme. Any business that purchases a water meter for monitoring water use can claim a 100% Enhanced Capital Allowance (ECA) on that purchase, allowing them to write off the cost of purchase and installation against their taxable profits in the first year of purchase.