Diverting Heathrow’s rivers

Rotork IQ intelligent electric valve actuators are being used in a 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 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 “Twin Rivers Diversion” project will be completed by 14 May 2004.

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