WET News

32 WET NEWS MARCH 2014 Different industries can experience different problems in monitoring water flow. For Centrica, the volume of water used at its Killingholme power station is key, while Wessex Water had to overcome algae issues. The challenge: Volume and algae flow issues P ower stations are heavily regulated and one key measurement is the vol- ume of water being used at any one time. This includes river water for cooling and normal water for steam generation. Excessive use incurs consid- erable fines. Centrica Energy, part of the British Gas Group, owns and runs Killingholme Power Station in North Lin- colnshire which is a combined gas turbine (CCGT) power sta- tion that began operation in 1994. It can send out more 3,000GWh of energy annually INSIGHT FLOW & LEVEL MANAGEMENT Top: The Ultraflow 3000 has been a solution for Centrica to measure the volumetric flow rate that enters the storage tank Below: The DFS-ll Doppler Flow Switch is designed for "dirty" liquids. The sensing is non-inva- sive, working by injecting high frequency sound through the pipe wall into the flowing liquid when the station is running at full load. At present the station runs a two-shiŠ system, which means they switch on and off twice a day allowing a competitive sta- tion with low losses. The station uses fresh water which is then conditioned for steam generation. Two hundred gallons of water can be used daily, through a 4" pipe from a mains water system. A flow meter is required to measure the volumetric flow rate that enters the storage tank; normal flow rate can be near 100m 3 per hour. The original meter broke down in 2011, and was found to be obsolete. Temperature Last year, Wessex Water experi- enced a problem where the flow sensors being used for confirmation of wash-water flow to plant and equipment were found to be growing algae. The thermal dispersion flow switch and the wash-water in the systems used either final effluent from the plant or par- tially treated water from some other point in the treatment pro- cess. The company discovered that the water content plus the increase in temperature on the probe was producing a food-rich and warm place for the propaga- tion of algae. This affected the thermal disper- sion from the probe to the point where the probes no longer detected flow. Removal from the pipeline would traditionally involve the isolation and drain- ing of the wash-water lines. n Two very different solutions were required, with Micronics selecting the Ultraflow 3000 and DFS-ll Doppler Flow Switch as its flow meters of choice. A solution: Clamp-on metering J on Dixon, Centrica's Con- trol Instrument technician determined that to avoid costly and disruptive downtime in the plant the replacement flow meter would have to be easy to fix without any need to break into the system. He compared suppliers and found that the Micronics Ultra- flow 3000 offered the best value for money and its operation has proved exceptional. It uses non-invasive ultra- sonic sound transmission and detects liquid flow velocity inside closed pipes; it is simple to operate and gives accurate measurements. Dixon explains: "When ultrasound is transmit- ted between the transducers, the speed at which the sound travels through the liquid is accelerated slightly by the veloc- ity of the liquid through the pipe. When ultrasound is trans- mitted in the opposite direc- tion, the flow of the liquid causes the transmitted sound to decelerate. The subsequent time differ- ence is directly proportional to the flow velocity in the pipe." There are considerable opportu- nities to use Ultraflow through- out Centrica's network and in similar applications in other industries, including in the Building Services, Energy Man- agement, Power Generation, Chemical, Pharmaceutical, Pet- rochemical and Food industries, where all that is required is to set up the product and calibrate it. It renders the use of mechan- ical meters unnecessary and is an excellent alternative to cut- ting pipes. It offers simple, low cost flow measurement from outside the pipe meaning that there is no interruption to process and no downtime whilst the flow meter units are installed. Wash-water flow Micronics Clamp-on Flow Switches provided a cost effective solution to eliminate the algae growth problem on flow monitoring of wash-water flow at Wessex Water Trant Construction identi- fied that a non-intrusive, cost- effective and simple to operate sensor that would not be sub- ject to fouling was required. It discovered the Micronics DFS-ll Doppler Flow Switch and agreed with the client to trial one unit for pipelines ranging from 32mm to 300mm, dependant on the velocity of flow through the pipework. The DFS-II is designed for "dirty" liquids. The sensing is non-inva- sive, working by injecting high frequency sound through the pipe wall into the flowing liquid. Acoustic pulses are continu- ously reflected back to the sensor and the DFS-II measures a fre- quency shiŠ to calculate flow velocity. It controls flow without any drop in pressure, no sensor fouling and minimal maintenance. The trial was suc- cessful and Wessex Water is now using the Micronics flow switches for most applications, including not only wash- water but pump dis- charge monitoring where some non-return valves had proved to be unreliable. n The kit: Pipe Sensor Nivus , www.nivus.com The Nivus Pipe Sensor was designed specifically to provide highly accurate flow measurement for potable water mains. Using a standard BSP fitting and gate valve, live tapping the pipe under pressure means fully operational sensors can be installed in hours. Using sensors set in a diagonal or V Emergency replacement service Z-Tech, www.z-tech.co.uk Z-Tech and Siemens can restore water flow meter telemetry within 12 hours and are offering a nationwide 24hr emergency replacement service. Water network, zonal, leakage and maintenance engineers all suffer when meters go wrong, said Z-Tech, and the innovative offer from the two companies ensures meter downtime becomes a thing of the past. Over the past ten years Z-Tech has replaced thousands of flowmeters in the water industry, shape measurement path, the Nivus ultrasonic transit time, or 'time of flight' measurement technique delivers accuracy comparable with the EMF. The NivuSONIC measurement principle is based on detecting the transit time of ultrasonic signals between two sensors. Simply the transit time in the flow direction is shorter than it is against the flow. Working closely with Severn Trent on a large scale project to use this technology for 900 proposed Mag Meter replacements across the drinking water network for 2015 developing a one-stop shop approach from enabling to reinstatement. Teaming up with Siemens ensures offers unrivalled availability of meters and fittings, said Z-Tech. Dale Snow, from Siemens, said: "We are delighted that we are the first to sparked an independent evaluation of the equipment at TUV NEL, the National Test facility in Glasgow. Proven results are now forging a partnership between Nivus, Morrisons and the water utility for a roll-out programme. offer this level of service; it comes from a long standing relationship with Z-Tech." Michael Swinhoe, Z-Tech's managing director, added: "This offer is designed to make life easier for the water industry."

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