Pneumatic automation solution for water pumping station

Much like the mainland UK, Guernsey has been greatly affected by the forces of nature this year. However, the use of a remotely controlled, pneumatically operated pumping station completed in 2013, has helped one area of the island to escape flooding. The pumping station is part of a network of facilities that forms Guernsey Water’s infrastructure for the catchment, storage and transfer of raw water for the production of the island’s drinking water.

Marais Stream pumping station was originally built in 1938 and required an upgrade to allow an increased volume of water to be collected and delivered to the nearby water treatment works with less going to waste. The whole infrastructure was changed apart from an old tank that remained. “There were two reasons for the upgrade, partly its age and partly because the area had, traditionally, suffered from a flooding problem,” explained Andy Benstead, water production manager at Guernsey Water. “The equipment is much bigger, more reliable, easier to control and we can now pump up to 1000 litres every second.”

Marais Stream collects the run-off water from the local area and this is fed via the three inlet penstocks through fine screens that remove debris that would damage the pumps in the pumping station. The water is then pumped either into the treatment works or, in the case of heavy rainfall can be diverted and discharged straight into the sea.

The pumping station is the first on the Island that could be considered ‘multifunctional’. It incorporates three vital elements. Firstly, raw water is caught and transferred into a reservoir for conversion into drinking water. Secondly, stream water is used to maintain the cleanliness of the screens at a new wastewater treatment centre. Finally, the new pumping station enables excess water to be pumped out to sea, which might otherwise overload the capacity of the Barker’s Quarry Reservoir and lead to localised flooding. 

“Festo supplied three pneumatically operated penstocks, driven by linear actuators, and located in the incoming channel, to isolate the flow,” explained Tony Gillard, business development manager at Festo. “DNC cylinders with rod clamps are used to control the raising and lowering of the penstocks. These distribute the incoming water into the storage basins. From the storage basins, the water is distributed to various parts of the site by butterfly valves operated by pneumatic quarter-turn actuators.”

The entire system is run by Festo’s CPX remotely operated control system. The site itself is unmanned, being controlled via a SCADA system from the Guernsey Water Offices five miles away. “The CPX platform is a complete automation solution that integrates a choice of pneumatic and electrical, analogue and digital I/O,” Gillard explains. “CPX systems configured for specific requirements are delivered pre-built, tested and ready for installation, enabling system integrators to meet tight deadlines and budgets. For additional flexibility, the CPX platform can operate as either a self-contained industrial PLC, or as a local unit on a fieldbus or industrial Ethernet-based distributed system. In addition, a wide choice of I/O and connector modules makes interfacing to process sensors and actuators easy.

“Remote operation is becoming more common and, with pneumatic control you have the functionality to remotely operate the system,” said Gillard.

Unusually for the water treatment sector is the selection of pneumatically controlled valves rather than electric. “On the mainland UK it is more usual to have electric actuators However, the advantages of pneumatics are beginning to sway the market,” said Gillard. “In most other applications, such as petro chemical and industrial applications, pneumatics are the preferred solution, but for some reason in water treatment and sewage plants electric actuation is still predominant for now.”

Pneumatic automation presents an extremely reliable alternative to electrical automation systems and reduces the costs of investment, installation and operation compared with conventional electrical installations.”

Guernsey Water has gone down the path of changing electric actuators to pneumatic and is reaping the benefits. Pneumatic control delivers energy saving, ease of installation, safety and reliability, because of less moving parts, as well as being faster to operate and easier to control.