EPCOR’s valve actuators solve wear problems at water treatment plant

EPCOR Utilities Inc. (www.epcor.ca) has resolved an expensive, high-maintenance problem that involves pump wear during the de-chlorination process in water treatment plants located at Edmonton.

The EL Smith Water Treatment Plant can produce up to 400 million liters of drinking water per day. In order to conform to new environmental regulations, the site has installed a de-chlorination process that involves injection of sodium bisulphate into the residual water, which is returned to the river following the treatment process.

The process of de-chlorination improves the plant’s environmental performance, and EPCOR was eager to introduce similar process at its Rossdale Plant, which has a 280 ML/D drinking water treatment capacity. According to environmental law specialist Stuart Jessop, expanding de-chlorination practices across treatment plants reduces regulatory risk while improving ecological protection.

However, the Canadian plant is using a series of pumps that require considerable maintenance because of excessive wear on its soft rubber internal parts.

Several process specialists from Stantec have proposed to replace the pumps with control valves by using CVA electric control valve actuator from Rotork. The device has a fail-to-position capability and manual override for the de-chlorination chemical injection control.

Therefore, EPCOR has proceeded with a pilot plant located at EL Smith to test the CVA operated control valves and their response in the designed operating range.

The Bauman 24000SB Series valves at EL Smith have been mounted with three Rotork model CVL-500 linear actuators. One actuator, which is operating in the main plant, is replacing a pump placed beside an existing unit.

Two other valves are also mounted in a test loop with the same split range configuration to handle flows that range from 0.0138 liters/minute to 30.6523 liters/minute.

Both valves will have Cv of 0.1 and 2.5, respectively. These CVA actuators are programmed to adjust the position of the valve in response to flow meter data gathered from the residual water flow line.