Dartford Road Tunnel and Bridge

Tunnel Monitoring and Control

• AIS are responsible for the design and development of a monitoring and control system that includes over 5000 input and output devices covering ventilation, lighting, fire systems, power distribution, emergency generation, pumping stations and weather forecasts.

• The system is based on a distributed PLC network with the SCADA software based on the latest web technology with user access via web browsers.

Life Safety System Design

• As part of the 'risk reduction measures' required under the new Road Tunnel safety regulations, Le Crossing are designing and installing a fire mist system in order to protect against fires in the tunnel.
• The design of the Fire Suppression and other life safety systems is being led by Jacobs with AIS and others providing specialist consultancy for fire identification and location, the control system design and the overall integration within the control desk.

Ventilation Control Upgrade – SIL2

• The first phase of the Life Safety Systems development is an upgrade to the ventilation control system to the safety system standard BS EN 61508, Safety Integrity Level (SIL) 2. The upgrade is based on dual Siemens FH400 PLCs for each tunnel with distributed I/O in the ventilation buildings.

• The Siemens PLC is approved up to 61508 SIL level 3 and AIS have used this as the basis for the overall SIL approval which is based on a life cycle approach to the development with verification and validation of the design at each stage.

• In normal operation the ventilation system provides pollution control and purging functions. In the event of a fire the ventilation responds to a set of pre-determined plans involving the jet fans, main and extract fans. Ventilation is initiated either automatically via the heat detection cable or manually by the controller. For reliability, the user interface for each tunnel uses a dedicated HMI terminal. In accordance with safety system development practices, the HMI has been prototyped, demonstrated and discussed with the controllers to ensure that it is simple and effective. An example from the HMI terminal is shown below, please click on the image for a larger view:

Heathrow - Terminal 5

• Balfour Beatty Rail contracted AIS to design and provide a technical specification for the tunnel ventilation control system for the rail tunnel linking the main terminal T5A to the satellite terminals T5B & C

• The specification included for a safety system design to meet SIL level 2 (BS EN 61508)

• Siemens led a small consortium with AIS and won the implementation project – which used Siemens Safety PLC and distributed I/O. The system controls twelve ventilation fans via variable speed drives and an extensive network of dampers to provide tunnel ventilation during normal operation and in the event of a fire. The system has over 2000 I/O signals distributed in twenty separate locations across the plant.

An example user interface screen from the dedicated HMI development.

The Track Transit System used to transport passengers to the satellite terminals.

Mersey Tunnels

Tunnel Pollution Monitoring

• MerseyTravel contracted AIS for the design and development of a pollution monitoring and SCADA system.

• The system includes fourteen sensors in the two Mersey Tunnels that monitor levels of CO, NO, Visibility and from NO derive NO2. The data from these is sent back to a Siemens PLC that feeds information into the existing SCADA system as well as a new overview mimic for both tunnels (See screenshot below).

• The system involved a phased installation and transition from the existing sensors to the new sensors and from the existing SCADA system to the new SCADA system.

Itchen Toll Bridge

• There are more than six million vehicle crossings on the Itchen Toll Bridge in Southampton each year. The bridge is owned and run by Southampton City Council, which uses the tolls as an instrument to regulate traffic flow in the city centre.

• In the late 1990s, SCC needed to replace its obsolete toll collecting hardware and software, as it was not millennium-compliant. It chose a custom system designed by AIS. This system was installed in November 1999 and has been operating successfully ever since.

• Tolls are collected at only one end of the bridge, where the road widens to a toll plaza with five lanes and four toll booths.