There was a problem at Wessex Water, a regional water and sewage treatment company in the southwest of England. 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 partially treated water from some other point in the treatment process. The water content plus the increase in temperature on the probe was producing a food-rich and warm place for the propagation of algae. This affected the thermal dispersion from the probe to the point where the probes no longer detected flow. Removal from the pipeline would traditionally involve the isolation and draining of the wash-water lines.
Trant Construction, who undertake Civil Mechanical and Electrical projects for major UK and overseas water companies were called in. They identified that a non-intrusive, cost-effective and simple to operate sensor that would not be subject to fouling was required. Various alternatives were considered until Dave Rich of Trant Construction 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 pipe-work.
The DFS-II is designed for “dirty” liquids. The sensing is non-invasive, working by injecting high frequency sound through the pipe wall into the flowing liquid. Acoustic pulses are continuously reflected back to the sensor and the DFS-II measures a frequency shift to calculate flow velocity. It controls flow without any drop in pressure, no sensor fouling and minimal maintenance. Installation takes just a few minutes because there is no need to cut into pipes resulting in a major saving in time and plant outage.
The trial was successful and Wessex Water are now using the Micronics flow switches for most applications, including not only wash-water but pump discharge monitoring where some non-return valves had proved to be unreliable.
Dave Rich is pleased with his choice. “I would definitely recommend the use of the DFS-II. The objective in this particular project was to eliminate algae in a cost-effective, timely manner. Micronics DFS-II fulfilled this objective as well as offering considerable other benefits.”
Voor meer informatie over dit project of de Micronics aanbod oproep Micronics op + 44 (0) 1628 810456, of bezoek www.micronicsflowmeters.com.