Rotork CVA actuator introduced to solve dosing pump wear problem at water treatment plants
Rotork’s innovative CVA electric control valve actuator has been introduced to solve a problem involving pump wear and resultant maintenance expense in the de-chlorination process at water treatment plants at Edmonton in Canada.
The E.L. Smith Water Treatment Plant is operated by EPCOR Utilities Inc. and produces up to 400 ML/D (million litres per day) of drinking water. To meet provincial 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 plant at E.L. Smith 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 the Rotork CVA, a precision electric actuator with manual override and fail-to-position capability, for the de-chlorination chemical injection control. EPCOR has therefore proceeded with a pilot plant at E.L. 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 E.L. Smith for the pilot project. One is replacing a pump sitting beside an existing unit and is operating in the main plant. The other two 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.