Improved reliability and safety at the water treatment plant, thanks to Rotork's EH actuators

Rotork's innovative EH electro-hydraulic range of heavy-duty valve actuators has proved to be a success in water and waste treatment plants.

A recent upgrade project at the Hap Cremean water treatment plant, serving the City of Columbus in Ohio, USA, is a good example. Here, the installation of EH actuators has prevented the re-occurrence of a potentially serious contamination problem caused by hydraulic oil spillage.

The Hap Cremean plant provides an average 70 million gallons of water per day, utilising six high service pumps, each with a 20 million gallon a day capacity to deliver the water. Each pump is fitted with a 30-inch ball valve that must be closed in the event of a pump failure to prevent the water from back-flowing into the treatment works. These valves were originally equipped with linear hydraulic cylinders and quarter-turn linkages, all six of which were powered by a central hydraulic power unit located some distance from the valves on a lower floor level.

A leak from the hydraulic circuit resulted in fifty gallons of the one thousand gallon oil system escaping and flooding the surrounding floor space. Apart from the obvious mess and inconvenience, the oil also presented a potentially serious risk of contamination to the water treatment plant. Not wishing to be faced with this problem again, the plant's operators decided to replace the entire existing hydraulic system and chose Rotork EH actuators for the upgrade.

Unlike conventional hydraulic actuators, the EH is a stand-alone design comprising a fully enclosed power unit containing an electric motor, hydraulic pump and reservoir. Combining the speed and accuracy of hydraulic positioning with the convenience of electrical operation, the EH also provides the benefits of simplified remote control and indication associated with electrical actuators. A specific feature of the integral controls is the ability to adjust the speed of valve travel to precisely meet important operating criteria (for example, maximum speed without inducing water-hammer), without resorting to conventional hydraulic flow control valves.

The EH actuator also eliminates the on-going operating and maintenance costs associated with traditional central hydraulic power units. As an added benefit at Hap Cremean, because each actuator requires only a few gallons of hydraulic oil, it was economically feasible to use a food grade variant which presents no risk of contamination in the unlikely event of a leak.