Electric actuators with variable motor speed offer an effective solution for the automation of large penstocks, whether in sewage treatment plants, retention basins or flood protection systems.

A modernisation project at Thames Water's Beckton Sewage Treatment Works demonstrates the key benefits of this technology. The upgrade included replacing existing actuators with high-performance AUMA SAV variable speed actuators. The new actuators help to preserve the operability of 12 large penstocks by reducing mechanical stress, while also enabling reliable and efficient process control.

Built in 1864 in the east London borough of Newham and extending over 100 ha (250 acres), Beckton STW is one of the largest sewage treatment works in Europe, serving a large portion of London north of the River Thames.

AUMA SAV variable speed actuators enable reliable and efficient penstock operation at Thames Water’s Beckton Sewage Treatment Works in the greater London area.

This project required adopting a “sympathetic” approach to working with the existing penstocks. AUMA recommended replacing the old single speed actuators with new, variable speed actuators. Variable speed technology allows the actuator motor to run at the optimum speed at each moment of the penstock’s opening or closing process. This allows the heavy penstocks to be operated gently, with soft starts and stops, thus reducing mechanical shocks whilst still being able to operate at higher speeds over the long travel to reduce operation time. 

All the new SAV variable speed actuators are fitted with individual automatic greasing cartridges mounted on the thrust bases. On each penstock’s rising stem, a single grease cartridge lubricates both the bearings and the penstock stem. The greasing cartridges are set to provide a timed release that extends the service life of the entire system.

Actuator controls include standard parallel controls with 24 V DC commands and 4–20 mA signals for position feedback. In addition, the actuators were fitted with Profibus interfaces. Although these are currently unused, the actuators will require no hardware or software changes to upgrade to Profibus control in the future.

On project completion, all 12 penstocks were fully tested and deployed. Site operatives are now able to work more efficiently, while Beckton STW is set to meet the challenges of the future.

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Thanks to their adjustable motor speed, AUMA SAV variable speed actuators reduce mechanical stress on twelve penstocks at the coarse screen outlets, helping to prolong their service lives.