28 May 2010
The Control Techniques software was fitted to a replacement Commander SK AC drive and is claimed to have cut callouts from ‘ragging’ - the fouling of the pump’s impeller - from a weekly occurrence to just once since it was installed six months ago.Ragging is a long-standing nuisance that eats up thousands of hours of maintenance time in sewage pumping stations and wastewater treatment plants worldwide. At the Kelly’s Bay pumping station, two variable speed drives control main and standby pumps. “The pumping station would run for a couple of weeks and then we’d get three or four call-outs in a week,” explains Fingal County Council’s mechanical supervisor Jim McGuiness. “So, when it was time to replace one of the existing 15kW AC drives, Control Techniques’ Drive Centre in Newbridge suggested that we had IPC Lite software loaded. It has worked extremely well, before the software we switched between the two pumps weekly to spread the load from a maintenance point of view. However since August we have just run the one pump with the IPC Lite software and monitored its performance by telemetry, maintenance costs have dramatically reduced.”Call-outs for blockages to Kelly’s Bay, a distance of some 11 miles, took a team of two an average of two hours each time, a significant maintenance burden and one that has now been virtually removed. The pump now runs continuously, with flow rates varying between 20 and 70 cu.m/hr with IPC Lite providing early warnings of ragging and initiating cleaning routines when required.IPC Lite is an in-drive solution to ragging that provides an early ‘predictive’ detection of a problem as well as initiating a client-defined cleansing cycle. It measures on-board active current unlike other systems that measure the motor’s nominal current – a measurement that can give an error of 30-40 per cent on the real torque figure. Control Techniques’ system measures real torque every millisecond. As soon as IPC Lite sees a change in the active current profile, remedial action is taken to remove the potential blockage. In the event of a blockage, the cleaning routine is initiated. The cleaning routine is user configurable via parameters and, in addition, a manual cleanse can be triggered by staff if required. To prevent repeated cleaning in the event of a major blockage, IPC Lite has detection of successive cleansings (in this case five times) and lock-out and alarm to indicate a fault. “We are very pleased with the IPC system and it has completely proved itself since its installation,” said Fingal County Council’s senior electrical and mechanical engineer, John Williams. “After checking our telemetry data over 12 months, it is clear that it has significantly reduced our maintenance costs. We are now looking at fitting IPC to the second riser and other problematic pumping stations are also under consideration. It is clearly cost-effective and is a low cost solution compared with costly macerators.”
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