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RT1 Linkspan Control System Upgrade

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Modernising a critical port asset to improve safety, reliability and long-term supportability

The RT1 passenger and vehicle linkspans at King George Dock form a critical interface between shore and vessel, enabling safe and continuous loading and unloading operations in a dynamic tidal environment. The linkspans rely on the coordinated performance of hydraulic, mechanical, electrical and control systems to maintain safe operating angles as vessel draft, loading conditions and tide levels change.

The original control system, installed in the early 1990s, was based on a single legacy PLC platform controlling both linkspans. While functional, the system had become obsolete, increasingly difficult to maintain, and limited in terms of diagnostics, resilience and compliance with modern standards.

Associated British Ports identified the need to replace the system with a modern, maintainable and safety-compliant control solution while retaining the established operational philosophy familiar to operators. FAIRFIELDS were appointed to deliver the upgrade, providing a long-term platform suited to the operational and safety demands of a busy port environment.

Scope of Works

The project involved a comprehensive upgrade of the linkspan control, safety and electrical systems, integrated with the existing hydraulic and mechanical equipment.

Key elements of the scope included:

  • Replacement of the legacy control system with modern Siemens PLC and safety architecture
  • Upgrade of motor control centres and control panels
  • Delivery of the MCC as a containerised solution
  • Integration of safety functions designed to ISO 13849 (machinery safety)
  • Installation of new instrumentation, including redundant inclinometers and wind monitoring
  • Development of new HMI interfaces for operation, maintenance and fault diagnostics
  • Provision of local and remote alarm annunciation and fault call-out
  • Segmented industrial communications network with cybersecurity zoning
  • Cybersecurity risk assessment aligned with IEC 62443
  • Factory Acceptance Testing (FAT), Site Acceptance Testing (SAT) and commissioning
  • Operator training, documentation and full system handover

The upgrade was designed as a functional like-for-like replacement while significantly enhancing safety, diagnostics, resilience and maintainability.

Key Challenges

The RT1 linkspans are safety-critical machines operating in a variable marine environment. The control system must safely manage linkspan level and inclination while preventing unsafe sequencing of climbing pins and hydraulic movements.

A key challenge was delivering a modern machinery safety system compliant with ISO 13849 while integrating with existing hydraulic and mechanical systems of varying age and legacy design.

Operational continuity was also critical. The works were delivered with minimal disruption to port operations through careful planning, staged changeover and proven fallback arrangements.

In parallel, increasing cybersecurity expectations required the control system to incorporate secure communications and network segmentation aligned with IEC 62443.

Delivery Approach

FAIRFIELDS adopted a structured end-to-end delivery approach covering design, build, testing, installation and commissioning.

Early project stages included development of the Functional Design Specification, supported by machinery safety assessment to ISO 13849 and a cybersecurity risk assessment aligned with IEC 62443.

A modern control architecture using Siemens S7-1500 PLCs and distributed I/O was developed, separating passenger and vehicle linkspan functions while maintaining coordinated control and safety interlocks.

The Form 4A Type 2 MCC was manufactured, assembled and factory-tested offsite within a 20ft container, creating a self-contained control and power solution. This containerised approach reduced on-site installation time, simplified commissioning and minimised disruption to port operations.

Offsite Factory Acceptance Testing of panels and software reduced risk prior to installation. Site commissioning was delivered in phases, with integrated testing across hydraulic, electrical and control systems prior to handover.

Outcome

The RT1 linkspan upgrade has delivered a robust, modern and compliant control system, significantly improving safety, reliability and long-term supportability.

The upgraded machinery safety system designed to ISO 13849 provides clearly defined and validated safety functions, improving protection for operators, vessels and infrastructure. Enhanced diagnostics and alarm handling deliver improved operational visibility and faster fault response.

Cybersecurity measures aligned with IEC 62443 improve system resilience and provide a secure foundation for future enhancements. The project provides Associated British Ports with a maintainable, future-proof control platform for a critical operational asset, while demonstrating FAIRFIELDS’ capability to deliver complex upgrades to safety‑critical maritime infrastructure.