Valves ease pump wear problems at water treatment plant
2 Aug 2010
Edmonton, Canada – Canadian company EPCOR Utilities Inc. has resolved a costly, high-maintenance problem involving pump wear in the de-chlorination process at a water treatment plants at Edmonton.
The EL Smith Water Treatment Plant is operated by and produces up to 400 million litres per day (ML/D) of drinking water. To meet new environmental regulations, the site has recently installed a de-chlorination process involving the injection of sodium bisulphite (NaHSO3) into residual water that is returned to the river after the treatment process.
The de-chlorination process improves the environmental performance of the plant and EPCOR was keen to introduce the same process at its nearby Rossdale Plant, which has a drinking water treatment capacity of approximately 280 ML/D.
However, the Canadian plant was utilising a series of pumps that were proving to require considerable maintenance due to excessive wear on the soft rubber internal parts.
Process specialists from water treatment experts Stantec proposed replacing the pumps with control valves using Rotork’s CVA electric control valve actuator – a device with manual override and fail-to-position capability, for the de-chlorination chemical injection control.
EPCOR has therefore proceeded with a pilot plant at EL Smith that will test the performance of CVA operated control valves and their response within the designed operating range.
Three Rotork model CVL-500 linear actuators have been mounted on Bauman 24000SB Series valves installed at EL Smith for the pilot project. One is replacing a pump sitting beside an existing unit and is operating in the main plant.
Two other valves are mounted in a test loop using a same split range configuration that will be used at Rossdale to handle flows ranging from 0.0138 litres/minute to 30.6523 litres/minute.
The valves will have a Cv of 0.1 and 2.5 respectively. The CVA actuators will be programmed to adjust valve position in response to flow meter data collected from the residual water flow line.
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