Design, Supply & Installation of an Impressed Current Cathodic Protection System for Driven H-Piles in Hong Kong

Date:January 2017
Capability:   Cathodic Protection
cathodic protection

Recently, Aegion completed a project for the design, supply, installation and commission of an impressed current cathodic protection (ICCP) system for over 240 nos. of driven H-piles. During the upgrading project for a government sewage treatment works, it was determined that one of the treatment tanks near seawater uses a deep foundation, which is supported by 242 pieces of large driven H-piles. These 12-inch square H-piles, roughly 150 lbs/ft universal bearing piles, are an average length of about 150 feet and are spaced between 6.5 and 16 feet from each other. To achieve a facility design life of 100 years and prevent the undue corrosion of the steel piles, an ICCP system was adopted to provide a cost-effective solution.

In the design stage, special considerations were taken in light of several specific project constraints:

  • Increased current requirement due to large total surface area of the piles and assumption of bare surface exposed to corrosive environment
  • Congestion of piles
  • Adjacent metallic objects near the H-piles that may be affected by stray current
  • Allowance for maintenance and replacement

After considering the factors above, an open-hole deep anode groundbed was adopted with an MMO anode placed in 32 holes at the same depth as the piles. The holes were distributed inside the pile caps to achieve a more even current distribution and terminated on the top of the tank structure to facilitate future inspection and/or replacement of anodes, if required. The whole ICCP system was powered by a total of seven transformer rectifiers. To mitigate the current interference to adjacent objects, stray current mitigation measures using bonding cables were adopted. Finally, performance of the ICCP system was monitored through silver/silver chloride and zinc reference electrodes installed at representative locations.

The ICCP system for the piles was commissioned in late 2015. The commissioning criteria was consistent with internationally recognizable standards, including EN13174:2001 and NACE SP0169-2007, with results showing the ICCP system performing satisfactorily.

Aegion Corporation

17988 Edison Avenue

St. Louis, MO 63005