Reliability fears for buried meters
It is much cheaper to bury electromagnetic flowmeters than install them in meter pits. But if things go wrong costs go up, and some water companies are experiencing more problems than they anticipated.
A reputation for reliability and low maintenance has led water companies to use electromagnetic flowmeters in large numbers. To reduce installation costs, some utilities have opted to bury meters rather than house them in meter pits, but the new practice may not be quite the cost-effective option hoped for.
South West Water currently avoids burying electromagnetic flowmeters, but has done so in the past. Five per cent of its flowmeters are buried, and the company said these had suffered reliability problems. North West Water was non committal about whether burial affected flowmeter reliability, but the company applied strict criteria when assessing how a flowmeter should be installed. A meter would only be buried when there is: “no requirement to access the primary element for maintenance, testing or adjustment .” The company will not bury meters in main roads or other situations where replacement would be “difficult or costly”. At Anglian Water, 60% of electromagnetic flowmeters are buried, with no reliability problems reported. Severn Trent meanwhile, is just embarking on a buried meter trial hence only a very small proportion of its meters are installed without pits. The trial has yet to yield any data.
Utilities have been concerned enough about buried meter problems to raise the issue with WRc. A spokesperson said WRc had received: “enquiries from water companies to look into the cost effectiveness of the practice,” the long term reliability and effectiveness of which was described as “unproven”. The spokesperson added: “One company [Thames Water] has buried an awful lot of them and recently stood up in a seminar and said they had to dig up more of them than expected.” Thames Water failed to respond to our questions, but WRc’s research into the matter will be completed by March 2001.
ABB Kent-Taylor supplies electromagnetic flowmeters to both North West Water and South West Water. Brian Franklin, the company¹s mass meter business manager, said ABB had been burying its meters for a long time and advised customers that burying should not be a problem. He added that in the last six years the company had buried many thousands of meters with a “very low” failure rate. The savings, he said, had been “massive”. Mr Franklin intimated that any drop in meter reliability was due to the quality of installation, not the fact it was buried: “If you do bury you need to be sure, before you backfill, that the cabling is okay. In the instances where there have been problems, this has not always been the case.”
Other sources also appeared to indicate that it is the cabling, and more importantly, quality of installation which can cause problems. South West Water said most of its problems stemmed from cable faults, particularly connections. North West Water said the main factor influencing the reliability of a buried meter was: “water ingress into the meter or more generally the cable through joints or damage”. The company also stressed the measures it now takes to minimise the risks of cable damage on the meters it buries: “The required length of cable is delivered ready potted from the manufacturer, with no intermediate joints. Any spare cable is coiled up and not cut.”
Clearly, there are great savings to made by burying electromagnetic flowmeters, providing installation is undertaken with care. Fail to do the job properly, and there is a risk of creating a false economy.
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