Flowmetering: The future
With climate change, carbon emissions and water scarcity increasingly on today's political agenda, the growing interest in leakage and revenue metering will drive demand for more sophisticated flowmetering, writes Tony Hoyle of ABB
The need to reduce leakage and energy expended on pumping water around the system is bringing the topic of flowmetering progressively into the regulators’ spotlight.
Operators are also becoming more aware of the options available, particularly for revenue metering and leakage monitoring. These options offer significant potential cost savings which can add to the bottom line, while helping to meet leakage reduction targets and improve network information.
Flowmetering in the water industry has been characterised by the use of traditional mechanical meters. Simple to operate and with a low price tag, these meters have long been seen as an attractive flowmetering option. But there are a number of things to remember about this type of equipment, all of which can lead to additional costs later down the line.
Firstly, it will only ever be truly accurate on the first day of installation. After that time, the meter’s accuracy will steadily deteriorate because of the inevitable wearing of the mechanical components. A loss of accuracy of a few percentage points may not appear that significant. But the potential loss of revenue that this under-registration represents is becoming of increasing interest as water companies look for ways to achieve more precise flow measurement and improve their profitability and levels of service.
The second thing to bear in mind is the meter’s total cost of ownership. This includes not just the cost of maintaining the meter, with its associated disruption as the meter is removed from the line, but also the cost of sending someone to manually collect information from several meters at a time.
The pressure being applied on water companies by Ofwat to more accurately identify and address leakages has already led some to employ new monitoring technologies. These feature additional capabilities, such as remote GSM-SMS communication, which enable leaks and other problems to be immediately traced and rectified.
Electronic flowmetering – the future?
Electronic flowmeters that work on the magnetic, ultrasonic and other principles, and incorporate electrical rather than mechanical sensing equipment, have been around in various guises for some time.
Yet, with the exception of the MagMeter, they have generally been slow to be adopted by the water industry. This has been due mainly to a comparatively higher purchase cost than mechanical metering equipment.
But, in most cases, payback on the installation of an electronic flowmeter could actually be achieved in a matter of days, as demonstrated by the following example.
Let’s assume we have a mechanical 152mm flowmeter, which is accurate to within ±2%. This flowmeter is installed in a line with an average flow rate of 25l/sec, which equates to an annual usage of 788,400m3. Assuming a cost just for water at £1/m3, over the course of one year, the inaccuracy of the meter would be losing the operator around £13,797 of revenue.
Now let’s assume we replace this meter with an ABB AquaMaster electromagnetic meter, which has an accuracy of ±0.5%. Based on the above flow conditions and water cost, the meter will pay for itself within just 23 days.
Nor is this the only area where an electronic meter can achieve savings. There are no mechanical moving parts that can be subjected to wear and which will need to be replaced. This not only ensures that the meter’s accuracy is constant throughout its service life, but eliminates the cost, time and disruption associated with removing the meter from the line for maintenance.
Developments in remote communications technology also mean it is now no longer necessary for staff to be deployed to read meters or check on their status. ABB’s AquaMaster flowmeter, for example, incorporates GSM-SMS communications technology, providing
operators with instant access to real-time data and also historical flow data logged by the meter. This technology has also made it possible to include a dial-out alarm, which warns the operators whenever a problem occurs.
Using portable in-situ equipment such as ABB’s CalMaster 2 verification tool, flowmeters buried underground or installed in underground chambers can now also be verified and tested from the surface, enabling easy and cost-effective performance checks without interrupting the continuity of water supply. This equipment can also be used to provide a diagnostic health check on the entire flowmeter system together with an early warning of any deterioration likely to lead to system failure.
Despite the cost benefits that electronic meters can bring, the water market in particular is still primarily dominated by their mechanical counterparts, and will probably continue to be so for many years to come.
What is becoming obvious, however, is the shift in emphasis among operators towards understanding the idea of cost of ownership, which takes into account all the costs incurred throughout the life of a flowmeter instead of just its purchase price.
One reason for this is the growing trend toward companies outsourcing responsibility for both supplying and running equipment to contractors, which must ensure they opt for the solutions offering best value for money over the long term.
Added to this is the capability of modern electronic flowmetering equipment to integrate with other equipment to provide operators with a wealth of information that was previously unavailable. When used with equipment such as data recorders and water quality monitoring devices such as turbidity monitors, flowmeters can be used to collect data that can be employed for uses such as improving water quality or optimising network performance.
To summarise, the water market is likely to see a steady rise in demand for electronic flowmetering, as users increasingly become aware of the benefits that these flowmeters can bring to the bottom line, in terms of reduced cost of ownership and the ability to identify areas where revenue is currently being lost. With in-situ verification, disputes over flowmeter measurements can be easily resolved without having to remove the flowmeter from line to be tested on factory calibration rigs.
Up to 700 AquaMaster electromagnetic flow meters from ABB are being installed as part of the transfer of responsibility for a significant part of the Ministry of Defence’s (MOD) water and wastewater assets to C2C Services, a consortium comprising Severn Trent Services and Costain.
The transfer of water services to C2C is part of Project Aquatrine, under which three contracts have been awarded to private sector partners. The C2C contract covers the North, East and South-east of England, and includes existing WwTWs, WTWs, pumping stations and, sewerage and water distribution systems on 1,500 MOD sites.
The C2C deal is the largest water and wastewater PFI project in Europe, valued at over £1B over its 25-year term. The MOD will pay C2C according to the amount of water it uses, so accurate metering is crucial. That’s where the AquaMaster meters come in.
According to C2C project manager Patrick Egan, the AquaMaster units were among the few meters that could match the MOD’s exacting specifications – in particular a requirement to maintain accuracy across a wide measurement range. “The meters are primarily being used as a mechanism for payment. That’s why they have to be so accurate,” he says. AquaMasters feature a measuring range of 1000:1 turndown ratio.
Another important factor in the decision to use AquaMaster meters is their ability to send daily reports via text messages. This ensures that flow data is readily accessible, making it easier for C2C to manage the network effectively. “The meters are identifying leaks and spotting trends. For example, if the water measured consumption on a site slowly rises over a month, something needs investigating. It could be legitimate increased activity or there could be a leakage problem that we need to address,” says Patrick Egan.
The project is currently halfway through, with the completion date set for
mid-2007. C2C is eventually looking to install between 600 and 700 AquaMaster meters on about 400 MOD sites. C2C also has plans to extend metering, monitoring and management services to a wider client base where water conservation and cost reduction is required.
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