How we designed and implemented a synchronised hydraulic bridge control system for Sisk
Bridges are unforgiving systems: public safety, tight schedules, heavy machinery and complex procedures. TAD’s blend of control engineering, robust documentation and manufacture allowed Sisk to deploy a solution that meets those realities – precise synchronisation, layered safety, and practical serviceability. Our approach was collaborative throughout, aligning with the bridge engineers to ensure the finished system meets specification and operates with confidence.
If you’re responsible for movable infrastructure – or any installation where synchronised hydraulics and public reliability are non-negotiable – we can help. Speak to us about safe control strategies, distributed cabinet architectures and commissioning support that keep people moving and ships on schedule.
Sisk commissioned TAD to design, document and manufacture a control system to raise and lower the pedestrian bridge serving London’s Leamouth Peninsula. The bridge is the main access route between the local train station and the peninsula; any unreliability would immediately inconvenience residents. At the same time, the crossing must be lifted safely and efficiently to allow large vessels to pass. The system, therefore, needed to combine public reliability with marine traffic coordination, while meeting stringent safety expectations.
We engineered a control architecture that drives four two-stage hydraulic rams in lockstep, maintaining positional coherence throughout the raise and lower cycles. The strategy blends real-time feedback, tolerance windows and controlled ramp profiles to prevent drift and shock loads, resulting in predictable, repeatable movement.
The solution spans four large control cabinets deployed across two plant rooms (north and south). This distribution shortens cable runs, improves service access and provides clear physical segregation, while the control logic maintains a unified state machine for the whole structure.
The system continuously monitors safety interlocks and performs real-time error checking across control components. Fault conditions trigger alarms and safe states, preventing inadvertent motion. Operationally, a dual-operator protocol – one controller on each side – adds supervised confirmation for critical steps, reinforcing mechanical and software interlocks with human oversight.
In addition to system design, TAD produced full documentation and manufacturing for the control cabinets, ensuring consistency from drawings to build to commissioning. This tightly coupled approach reduces ambiguity during installation and supports long-term maintenance.
Movable bridges pose a familiar but demanding coordination problem: heavy structures, multiple hydraulic actuators, and a public environment that tolerates very little downtime or drama. At Leamouth, the control system had to synchronise four, two-stage hydraulic rams, keep motion smooth under variable loading, and constantly verify that interlocks and subsystems were healthy. With control cabinets split across two separate plant rooms on the north and south sides, we needed a distributed design that behaved as a single, deterministic system. Operationally, procedures had to be robust enough for daily use but flexible enough to respond to shipping schedules – two operators, one per side, would provide an additional layer of safety and coordination.
The Leamouth Bridge control system now delivers smooth, reliable operation in both directions, supporting the daily rhythm of residents while enabling timely openings for large vessels. Continuous diagnostics and interlock monitoring reduce unexpected stoppages and help engineers resolve issues swiftly, while the dual-operator procedure gives local stakeholders confidence that every movement is checked and coordinated. The distributed cabinet design eases servicing and future upgrades, and the overall system behaviour is calm and predictable – exactly what a public-facing movable bridge requires