Preserve and enhance historic rivers at Heathrow


Preserve and enhance historic rivers at Heathrow

Rotork IQ valve actuators are being used in an ecologically important "Twin Rivers Diversion" project associated with the construction of the new Terminal 5 (T5) at London Heathrow Airport.

Twenty-three actuators operate stainless steel penstocks manufactured by H. Fontaine Ltd to control the flows within new open channels, built to divert the courses of two of London's historical rivers around the western perimeter of the 260ha Heathrow T5 site.

David Palmer of Black & Veatch Consulting and Rivers Team Leader at T5 owners BAA plc explains: "BAA opted to divert the Longford and Duke of Northumberland's Rivers around the western perimeters of the airport rather than bury the existing courses in culverts beneath the proposed development. The new diverted channels have been designed with significant ecological enhancements in order to maximise the environmental values of the rivers."

At the head of each channel, off-take structures incorporating seven 1.5 metre wide penstocks are operated automatically by Rotork IQ25 actuators in response to analogue signals from adjacent ultrasonic level sensors installed in the river beds. The actuators are fitted with Rotork Folomatic proportional controllers and CPT current position transmitters to enable progressive penstock movement and position signalling to commence when the "bank full" trigger level is approached downstream of the off-take structures. The actuators continue to shut the penstocks until the water level is stabilised, ensuring that the rivers are kept full but the banks are not breached. A telemetry link from each installation transmits information on penstock status, positions and upstream/downstream water levels to a central control room at Heathrow Airport.

The Fontaine penstocks feature fully enclosed operating mechanisms with bevel gearboxes, enabling the Rotork actuators to be installed in ergonomically convenient positions. This facilitates access to the actuators during installation, inspection and maintenance and removes any requirement for high level walkways or temporary scaffolding.

The "Twin Rivers Diversion" project was started in November 2002 and will be completed by 14th May 2004