Client – Rio Tinto
Consultant – Infracorr Consulting
Contractor – Duratec Australia Pty Ltd
Date – July 2011
Dampier Salt Dolphins are located at Dampier North Western Australia, 1533 kilometres north of Perth in the heart of the Pilbara. Dampier is the world’s largest exporter of high-quality salt.
Mooring dolphins are used to facilitate the docking of large ships offshore to secure for loading purposes.
The Dampier Salt Dolphins are an integral asset to facilitate loading requirement and berthing facilities. The structures are prone to some of the worst conditions in the world, this includes tidal, humidity and a cyclone prone area within a marine environment. The concrete structures are suffering from steel reinforcement corrosion due to exposure to high concentrations of chloride and moisture at elevated temperatures.
Concrete spalling and exposed corroded reinforcement was observed in the initial condition assessment. Infracorr Consulting was appointed by the client to perform a diagnostic assessment of the concrete elements for the purpose of rehabilitating each dolphin.
The dolphin repair project included: hydro-demolition of concrete; reinstatement with gunite; removal and replacement of the fenders; installation of a hybrid CP system for the protection of the concrete reinforcement and pile wrapping.
The Duoguard Hybrid Anode corrosion control treatment was chosen in preference to an impressed current system. A permanent power source was not an option for the remote site due to the cost. Both the Hybrid and galvanic systems were considered, however due to the environment and condition of the structure the Hybrid Cathodic treatments was evaluated as the most cost-effective option.
Access to Dolphin works site was via heavy works barge and tethered vessels to complete corrosion control contract works by Duratec Australia.
The Duoguard hybrid cathodic protection system was installed to ensure similar performance equivalent to traditional ICCP systems however with lower installation and ongoing costs. The hybrid system was chosen as the most practical corrosion treatment system, only loose or delaminated concrete was removed. A permanent power source wasn’t available or an option therefore this was an attractive benefit to suit the Hybrid system.
Monitoring has been designed to allow regular and cost-effective remote monitoring of the systems performance from anywhere where there is Internet access.
Monitoring thus far indicates that the Hybrid system is protecting the reinforcement as the design had intended.