Cathodic Protection Swanson Dock West
CLIENT: Freyssinet Australia for Port of Melbourne
The Cathodic Protection of Swanson Dock West remains one of the largest and most innovative Impressed Current CP Projects in Australia. The ICCP systems protect the Concrete Beam and the steel pile and sheet pile substructure running the length of the 1 km long wharf with a total design current of 3600 Amps.
The Swanson Dock West CP project incorporates three separate Impressed Current Cathodic Protection (ICCP) systems to protect the 30 year old structure, including :
• Concrete Transverse Beams
• Concrete Fender Beam Sections
• Water Anode CP to Steel Piles & Sheet Piles
These systems are briefly described below.
CONCRETE TRANSVERSE BEAMSThe transverse beams are approximately 14m long and 1m wide and are above the high water level except for the front 4m which is tidal. The beams required delamination and spalling repair prior to the CP installation. The ICCP system designed incorporated Titanium internal anodes (400mm long) installed in drilled holes from either side of the beam. The anode spacing varied subject to the reinforcement density and averaged 250mm. The design incorporated 2 vertical zones to allow for the tidal effects on the system. The design was trialed and tested on one beam prior to the final installation which included:
• 44 beams, 18,000 internal anodes
• 18 zone, 88 sub-zones
• 72 references
• 90 Amp design current
CONCRETE FENDER BEAM SECTIONS
A total of 30 x 3m long sections of the fender beam were strengthened to accommodate the new fender system and incorporate the ICCP system. With the fender sections above the high tide level, Titanium ribbon anodes were installed into the reconstructed sections with a dry spayed concrete overlay. The overall fender system included:
• 30 x 3.5m long reconstructed sections
• 1000m Titanium ribbon anode
• 6 zones, 30 sub-zones
• 30 references, 30 Amp
The water anode system to protect the bare steel piles, sheet piles and submerged concrete beams required a very large current of 3500 Amp based on 120mA /m² steel.
The innovative design was based on the first ever application of the “multiplier” CP technology where the Power to the water anodes was distributed at high voltage DC (300V) and converted to low voltage by a ‘multiplier’ placed near the cylinder Ti anodes. This allowed the distribution cables (up to 600m long) to be greatly reduced in section (2.5mm²) and resulted in massive power savings over the life of the system.
The water anode system included:
• 77 Ti Cylinder anodes, 77 Multipliers
• 39 Rack mounted Transformers
• 3500 Amp
• 85% efficient ($1m power saving over life)
The T/R’s for the systems are mounted in air conditioned buildings at each end of the wharf.