Description

As part of Boston’s “Big Dig” project, SPEC commissioned the ventilation fan control system for the northbound Liberty Tunnel, monitoring traffic and life safety conditions.  The northbound tunnel was opened on schedule in 2002, the southbound was opened on schedule in 2004.

SPEC provided detailed design with hardware provided by Square D / Modicon to meet the project specifications from Jacobs / Sverdrup Engineering who provided the schematic design. SPEC also developed the PLC code in compliance with IEC – 1131.1 to create reusable function blocks . This approach reduced the amount of software development time and made the Factory Acceptance and Site Acceptance Testing predictable and manageable.

The control system monitors traffic and life safety conditions and adjusts the amount of supply air to meet specific real time conditions within the tunnel network, via VFD’s. Monitoring of fan bearing temperature and vibration insure that each system is maintained in good working order. SPEC developed the Operator Interface Screens shown below using Intellution FIX HMI Package.
Typical Centrifugal Exhaust Fan HMI Screen.

Typical Jet Fan HMI Screen

The Jet Fans used in this project are strategically placed within the Tunnel System to quickly evacuate Smoke and Carbon Monoxide should a critical level be reached. All systems report to the Operations Control Center so that Exhaust and Jet Fan speeds can be optimally tuned to match traffic flow conditions.