Sarah Mildred Long Bridge

In 2018-2019, Panatrol Automation & Controls played a pivotal role in the award-winning Sarah Mildred Long Bridge Replacement project, a landmark infrastructure endeavor connecting Portsmouth, New Hampshire, and Kittery, Maine. This $163-million vertical-lift bridge project not only modernized a critical transportation link but also set new standards in safety, innovation, and automation.  

Panatrol’s Role: Advanced Control System Integration

Panatrol was entrusted with designing and implementing the bridge’s sophisticated control systems. Their scope of work included:  

• Backup PLC System: Ensuring system redundancy and reliability.

• Fully HMI-Controlled Operations: Eliminating the need for manual pilot devices, enhancing operational efficiency.

• Redundant HMIs: Providing multiple human-machine interfaces on the operator console for seamless control.

• Tower Drive Lift Bridge Mechanism: Managing the vertical-lift operations of the bridge span.

• Skew Control System: Utilizing networked absolute encoders and Panatrol’s proprietary algorithm to maintain the 300-foot movable span within a ½-inch height differential from end to end.  

This meticulous attention to automation and control ensures that the bridge operates safely, and with unparalleled precision.

Engineering Excellence and Recognition

The Sarah Mildred Long Bridge project was recognized for its innovative engineering solutions:  

• Precast Concrete Segmental Towers: The bridge features the first-ever precast concrete segmental towers on a vertical-lift bridge in the U.S., enhancing durability and reducing maintenance necessary.

• Reduced Bridge Openings: With a vertical clearance of 56 feet in its resting position, the bridge requires 68% fewer openings, significantly improving traffic flow.

• Safety Milestone: The project was completed with over 600,000 safe work hours and zero lost-time injuries.  

These achievements earned the project multiple accolades, including ENR New England’s Project of the Year and the ACEC National Grand Award in 2019 .  

Panatrol Automation & Controls’ contribution to the Sarah Mildred Long Bridge Replacement exemplifies their commitment to delivering cutting-edge automation solutions in complex infrastructure projects. Their expertise ensured the bridge operates with exceptional precision, safety, and reliability, setting a new benchmark in bridge automation.

To see more of our projects, visit our Projects page.

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