TRURO TIDAL GATE

Flood defense hydraulic system designed to DIN19704

Main Contractor:
Kier

End User:
The Environment Agency

Overview

Truro Tidal Gate is a strategically important asset that plays a critical role in managing flood risk and protecting 45 homes and 140 businesses in the commercial centre of Truro.

The gate provides protection from tides of a certain magnitude during periods of high river and surface water flow. Having not benefited from major capital maintenance, testing identified that elements of the existing system had become worn, obsolete and reached the end of their serviceable life.

The project to install the new tidal gates began in 2023, with IMH brought in to design, manufacture, install and commission the tidal gate hydraulic system required as part of the wider flood defence upgrade.

The Truro Flood Defence Upgrade

A key location on the Truro River was selected to allow the project to take place during low tide, removing the requirement to close the gates during the work.

Contingencies were put in place in the unlikely event that the gates needed to be operated during the project. This would have involved installing temporary flood barriers, known as stop logs, at the gate structure.

The contingency measures were ultimately not required and, during the 16,000 hours worked on the project, no serious incidents were recorded.

Having previously worked with the Environment Agency on numerous flood gate projects, IMH was able to bring its hydraulic engineering experience to the Truro project.

Designing the Tidal Gate Hydraulic System

Working closely with Kier Natural Resources, Nuclear & Networks, AtkinsRéalis and Centregreat Engineering, IMH engineered a hydraulic solution designed to operate using biodegradable hydraulic fluid.

The IMH team used specialist HydroSYM software to design the hydraulic system before producing the mechanical drawings using SolidWorks.

The system was designed in accordance with BS EN ISO 4413 – Hydraulic Fluid Power General Rules & Safety Requirements for Systems and their Components.

The resulting hydraulic flood gate system was designed to provide reliable normal operation alongside additional measures to allow the gates to continue operating in the event of an emergency.

Flood Gate Hydraulic Power Unit

The flood gate hydraulic power unit incorporates a 7.5kW electric motor-powered hydraulic pump for normal operation alongside a diesel engine-operated pump that can be used in the event of an electrical power failure.

The system can also be placed into a ‘float mode’, allowing the gates to be manually operated in an emergency.

The completed hydraulic system allows the gate to open in just 2 minutes 20 seconds and close in 1 minute 40 seconds, providing a fast response to rises or fluctuations in tidal flow.

All pipework Take-Over-Points (TOP) on the hydraulic power unit were configured to suit the specific site conditions and layout of the hydraulic equipment.

This prevented crossover of the pipelines during installation while also providing a cleaner pipework arrangement.

Each TOP was also equipped with an isolation valve that could be padlocked in both its fully open and fully closed positions.

Hydraulic Control and System Protection

The system pressure gauges incorporated into the HPU design were supplied with stainless steel casings and panel mounted.

To help prolong their working life, the gauges were glycerine filled and designed for a maximum pump pressure of 138 bar.

Each function is individually controlled by dual solenoid-operated directional control valves mounted directly to a manifold located on the tank lid.

To help prevent potential damage to the mechanical structure, each function also incorporates reduced pressure capability to limit the pressure applied to the extend side of the cylinder.

These features provide greater control over the operation of the tidal gate while helping protect the wider mechanical system.

Hydraulic Fluid Filtration and Environmental Protection

Environmental considerations formed an important part of the hydraulic system design.

To maintain the cleanliness and correct flow of hydraulic oil throughout the system, the fluid is filtered after leaving the pump and again before returning to the reservoir.

The wider project focused on responsible waste management and the reuse of materials. Fuchs PlantoHyd 32 was selected as the hydraulic fluid due to its environmental credentials and suitability for applications involving natural water sources.

The hydraulic power unit is also installed within a bunded frame, providing containment and an additional layer of environmental protection in the unlikely event of a leak or spill.

Project Outcome

IMH successfully designed, manufactured, installed and commissioned the hydraulic system forming part of the Truro Tidal Gate flood defence upgrade.

The completed solution combines electric and emergency diesel-powered operation with manual float functionality, hydraulic fluid filtration, environmental protection and a gate operating time of 2 minutes 20 seconds to open and 1 minute 40 seconds to close.

The wider project contributed more than £600,000 to the local economy and supported a range of social benefits.

The new tidal gates will provide flood protection to 185 homes and businesses in Truro for the next 30 years while helping minimise the environmental impact of the flood defence infrastructure.

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