Minnesota Slip Bridge

Project Overview

Located along Duluth’s bustling waterfront, the Slip Bridge serves as both a critical pedestrian crossing and a passageway for boat traffic in the Minnesota Slip area of Lake Superior. Historically plagued by mechanical and control system failures, especially in high winds common to the region, the bridge was frequently stuck in either the up or down position, disrupting both marine navigation and pedestrian crossing.

In 2016, a comprehensive redesign was undertaken to address these chronic reliability issues. Panatrol Automation & Controls was trusted to rework the bridge’s outdated control systems and support its mechanical modernization.

Panatrol’s Role: Reliable Control for a Demanding Environment

Panatrol played a key role in ensuring the redesigned bridge operated with reliability, precision, and resilience. The upgraded system now supports up to 20 bridge openings and closings per day - without mechanical fault - even under wind gusts that previously would have disabled it.

Control System Modernization Highlights:

• Conversion to PLC-Based Control: Panatrol replaced the aging relay logic control system with a modern programmable logic controller (PLC) system, significantly improving automation, diagnostics, and long-term serviceability.

• Drive Integration and Precision Speed Control: Rather than replacing the Rockwell 700 series inverter drives, Panatrol enhanced their capabilities by installing Ethernet interface cards. This allowed precise motor speed control via the new PLC - moving from open-loop to a more refined, coordinated control strategy.

• Redundant Position Feedback: Redundant inclinometers were installed on each bascule leaf to provide real-time feedback on bridge position, ensuring safety and reliability through continuous monitoring.

• Legacy Cable Preservation: Much of the existing electrical cabling - especially within the underwater duct system - was preserved to reduce cost, limit installation risks, and maintain environmental compliance.

Mechanical Redesign Synergy

Panatrol’s control upgrade worked hand-in-hand with major mechanical system improvements, including:

• Dual redundant motors per leaf

• A common parallel shaft speed reducer

• Floating shaft assemblies

• Rack beams, pinions, and carriage assemblies

Together, these updates dramatically improved the bridge’s ability to perform consistent, smooth operations in demanding conditions.

Project Impact

With Panatrol’s expertise in modernizing industrial and infrastructure control systems, the Duluth Slip Bridge has transformed from a high-maintenance liability into a dependable public asset. The bridge now functions under conditions that once caused regular failure - supporting maritime activity and enhancing pedestrian accessibility in Duluth’s vibrant waterfront district.

Explore more control system services from Panatrol at https://www.panatrol.com/services/hmi-scada-design

‍