CURRAGH MINE COAL TANK
Curragh Mine Coal Tank
CLIENT: Wesfarmers Curragh
The reinforcement corrosion and concrete spalling was due to the presence of chloride contamination in the walls of the Coal Thickener Tank at the Curragh Mine. Infracorr Consulting designed, specified & supervised major concrete repairs and the installation of a Hybrid Corrosion Prevention system to extend the life of the tank, the design enabling Wesfarmers to put the tank back into full service without major interruption to mine operations.
CHALLENGESThe design required the concrete repair works to be performed and sufficiently cured within a 2 week shutdown period, after which time the plant and equipment loadings would be reapplied to the walls and the tank put back into service.
As the extent of reinforcement corrosion was such that simple ‘patch’ repairs would not be sufficient to provide the 30 year life extension to the tank required by Wesfarmers, a cathodic protection system needed to be designed to achieve this aim.
The design required the concrete repairs to be performed as rapidly as possible. Hydro-demolition was chosen to remove all the delaminated concrete, and dry-process gunite application selected to backfill the repair areas.
The Hybrid system was considered by Infracorr to be the optimum solution for Wesfarmers, as:
• It eliminated the need for a permanent power supply.
• It significantly reduced the extent of permanent cabling and conduiting.
• It will minimise the ongoing maintenance costs.
In total, over 9000 individual anodes were installed at a spacing of 250-350mm, all while the tank was back in full service. A temporary power supply applied a 12 Volt DC current during the initial Impressed Current Phase of 7 days. Once the design criteria was achieved, the anodes were connected in Galvanic mode for the ongoing protection to the reinforcement.RESULTS
The hydro-demolition/dry-process gunite concrete backfill techniques were successful in completing the concrete repairs within the 2-week shutdown, thus allowing the tank to be put back in, service in accordance with Wesfarmers program.
The Hybrid system has been designed to allow regular and cost-effective remote monitoring of its performance from anywhere where there is Internet access. Monitoring thus far indicates that the Hybrid system is protecting the reinforcement as the design intended, i.e. it will provide a 30 year life extension to the tank.
The repair works were undertaken by Freyssinet Australia and Marine & Civil Maintenance joint venture. Supervision and commissioning was completed by Infracorr.