Skilmatic actuators provide 'dry bedding' solution

Rotork Skilmatic valve actuators provide solution to 'dry bedding' at water treatment plants.

When Rotork Gears' company Exeeco were asked by United Utilities to solve a 'dry bedding' sand filter problem at water treatment works serving the north west of England, they were able to submit an ideal solution using Rotork Skilmatic actuators.

The problem was recognised after several power failures had led to 'dry bedding' in filter beds, caused by delayed closing of outlet valves, jeopardising the quality of the water reaching the reservoirs. It was decided that the process needed to detect a power failure in order to put the treatment plant inlet and outlet valves on 'standby' until the back-up generators cut in.

On some of the pumping stations an uninterrupted power supply (UPS) was the obvious solution, but this was deemed to be too costly and require too much maintenance to be seen as the universal solution. However, these drawbacks could be overcome using Rotork Skilmatic fail-safe electric actuators.

The Skilmatic actuator is a totally self-contained fail-safe electro-hydraulic design capable of continuous modulation duty and fail-safe action on loss of signal or power supply.

On power failure the Skilmatic actuator is programmed to automatically go into standby mode for a predetermined time, after which, if the back-up generator has not started, it prevents the filter from running dry by closing the outlet valve be means of its integral spring return mechanism. This successful solution saves the expense of installing separate pneumatic systems or back-up batteries.

Carl Tetlow, United Utilities Project Engineer explained: "We approached Exeeco as our actuation specialists to design a specific solution for this problem. Their specialist knowledge of actuators and applications provided us with an excellent technical and economical solution that addressed all our concerns. We were delighted with the support we received throughout the contract and would have no hesitation in considering this product to extend the scope to other treatment plants in the North West."

Exeeco Sales Director Ian Elliott adds: "We were pleased with our solution to this project as it has avoided the customer incurring the large expense of installing UPS or battery back-up systems, which were the customary fail-safe systems until we devised our simple but effective alternative."