Siemens helps secure safety of Heathrow T5
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BAA turned to Siemens and its tunnel-systems partner Applied Industrial Systems (AIS) when it needed a control system for the tunnel ventilation at Heathrow’s Terminal 5.
To ensure the safety of passengers and staff travelling on the train that links the main terminal (T5A) to the satellite terminal T5B, the system for ventilation and smoke control (in the event of fire) needed to meet safety standard BS EN 61508 Safety Integrity Level (SIL) 2.
The Siemens and AIS solution integrated a number of Siemens products with third-party equipment.
The core component is the Siemens S7-400FH dual fail safe and high reliability PLC, which is certified up to BS EN 61508 SIL level 3.
The Siemens PLC links via a dual network to dual I/O racks, controlling fans via variable-speed drives, and dampers via Rotork actuators.
The system also features an engineering PC that runs Siemens’ WinCC Scada software.
This PC controls and tests all the input and output devices on a regular basis to ensure they are functioning correctly.
It also reads the torque curves from each of the dampers to ensure they are in good condition and can operate when required.
The whole philosophy behind the system design and development was an active approach towards safety and the on-going safe operation of the system.
The Siemens S7-400 FH PLC will eventually be required to interface to a total of 2000 I/O points.
It can control the operation of the ventilation system from T5A to T5B and expand to cover the second satellite terminal, T5C, which is due to open in 2011.
The control system meets the requirements of BS EN 61508 Safety Integrity Level 2 and satisfied the requirements of Her Majesty’s Rail Inspectorate, which was necessary for BAA to run the train and use the tunnel for passenger movements.
The system will be able to expand to meet the needs of T5C in 2011 and further still, if necessary.
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