Intelligent valve actuators fitted at Gatwick

Rotork intelligent electric valve actuators and two-wire digital control systems are at the centre of a modernisation project on the aircraft refuelling infrastructure at London's Gatwick Airport

Rotork intelligent electric valve actuators and two-wire digital control systems are at the centre of a vital modernisation project on the aircraft refuelling infrastructure at London's Gatwick Airport.

The scheme is part of a strategy designed to increase the airport's annual passenger throughput to 40 million by 2008.

Last year 30 million passengers used Gatwick, served by more than 260,000 aircraft movements requiring 2.6 billion litres of Jet fuel.

The underground system that distributes this fuel has been recently extended to a new area of the airport and now serves 260 refuelling points on 110 parking stands in three separate areas on the 759 hectare Gatwick site.

The aircraft fuel distribution system is operated by Gatwick Airport Storage and Hydrant Company (GASHCO), a consortium of major oil companies.

GASHCO also owns and operates the airport tank farm facility and is managed by Shell UK Ltd.

With a total length of 14 kilometres, the underground system comprises pipework ranging in diameter from 600mm to 150mm, itself holding 1.8 million litres of fuel, supplied from three 12,000 cub.

metre storage tanks.

Refuelling operations, involving pumping fuel at flow rates of up to 54,000 litres per minute, are performed on a 24 hour basis, with activity normally peaking between early to late morning.

Following on from the extension project, the control system for the entire network is now being upgraded to introduce fully automatic, centralised monitoring and operation.

Rotork Retofit engineers, working to strict timescales and in close co-operation with the operators and other contractors to avoid any disruption to the normal operation of this crucial airport activity, have installed new actuators and upgraded the control circuits in those already installed.

New IQ intelligent actuators, with Rotork Pakscan 2 wire connectivity, have been installed on valves in the tank farm and apron areas to control the flow of fuel throughout the network.

The actuators also have the function of isolating specific pipeline sections in the event of any localised emergency, enabling the rest of the network to operate normally.

Rotork actuators already installed in the network have also been retrofitted with Rotork Pakscan cards to enable them to be linked into the new control system.

As with the Pakscan connectivity built into new actuators, the retrofitted cards are fitted inside the actuators' double-sealed watertight enclosures.

This is a particularly important consideration for those actuators installed in underground valve chambers on the apron areas.

Due to the high water table at Gatwick these chambers are vulnerable to excessive ingress of water, with the actuators operated in a continuously damp atmosphere.

However, Mike Ling, manager for Shell, confirms that the Rotork actuators continue to perform well in spite of the severe conditions in which they operate.

Rotork Pakscan enables the actuators to communicate valve positional, status and diagnostic data to the centralised control system by means of a 2-wire serial loop with dramatically reduced cabling costs.

For maximum security and operational flexibility the pipeline is divided into three separate Pakscan loops which are programmed from individual master stations in the central control room, sited by the tank farm.

The Pakscan monitoring, operating and interlocking functions are controlled by a Modicon Quantum PLC which is operated by the Fix Dynamics SCADA system that now supervises all fuel pipeline activities.

As an integral part of the SCADA function, the Rotork actuators are programmed with their ESD (emergency shut down) overrides activated to signal, record and immediately action failsafe valve closing sequences if an unauthorised event occurs.

In addition, an independent actuation control back-up is provided by Rotork's Pakvision PC-based software.

The dedicated Pakscan control and monitoring package can be operated in the control room if there is a problem with the SCADA system.

The new control system, which was designed and installed by control specialists Real Time Engineering, has built-in capacity to handle the further expansion and modernisation planned for future airport developments.

With the anticipated increase in Jet fuel demand, the built in capacity has provision for additional pumping capacity, the motorisation of the remaining hand operated valves in infrequently operated valve chambers on the airport aprons and the integration of other Rotork actuators situated in the tank farm.

The design and expansion of the airport fuel system and tank farm modernisation at Gatwick has been the responsibility of the Operations Projects team of Shell Aviation Limited, London.

Mike Ling summarises the importance of its successful completion: "This ambitious project has been skilfully carried out by all involved partners and will ensure that the airport refuelling systems meet with the anticipated increase in fuel demands at Gatwick well into the future.".

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