Post-earthquake remedial work

Citation

(2000), "Post-earthquake remedial work", Anti-Corrosion Methods and Materials, Vol. 47 No. 6. https://doi.org/10.1108/acmm.2000.12847fab.006

Post-earthquake remedial work

Post-earthquake remedial work

Keywords BAC Corrosion Control, Pipelines

Only months after completing its contract with Thames Water to design, install and commission the corrosion protection system for the 140km pipeline transporting water from the Yuvacik dam and water treatment works to Izmit and Istanbul, BAC Corrosion Control engineers found themselves back in Turkey surveying the system for damage after the tragic Izmit earthquake in August last year.

The 2.2-metre diameter steel pipeline, constructed under Turkey's first build, operate and transfer contract, follows the Sea of Marmara northern coastline from Izmit towards Istanbul, feeds 24 reservoirs and has six pumping stations. The BAC impressed current cathodic protection (ICCP) system is based on silicon iron anodes in conventional horizontal coke breeze backfilled groundbeds, of which there are nine along the pipe's route. The pipeline has been laid virtually at sea level and at one point is fully encased in concrete and constitutes the local sea defences. BAC also provided the corrosion protection systems for other structures within the project including sections of the smaller diameter ductile iron feed mains.

BAC had been working with Thames Water, the main Izmit Su AS international joint venture partner, on the Izmit Domestic and Industrial Water Supply Project since 1996. It was therefore natural that, when a post-earthquake pipeline audit was needed, the company was called in by Thames Water, to survey not only the ICCP system but also the pipeline itself, particularly where it could not be seen. Apart from a major defect where the fault line crossed the pipeline (Plate 2), there was no really serious damage. BAC is currently undertaking the necessary minor remedial work to the ICCP system using some of Turkish labour it employed when the system was being constructed.

Plate 2 BAC digs into remedial work following post-earthquake pipeline audit for Thames Water in Turkey

Impressed current cathodic protection systems employ inert (non-galvanic) anodes with an external source of DC power to impress a current from anode to cathode (pipe) through the soil. Voltages are applied to overcome soil resistance to give a spread of protection of up to 50km or more for well-wrapped pipe under cross-country conditions.

Anodes are commonly used in groups buried in a low resistance backfill called a groundbed. ICCP systems are considered to be the most efficient cathodic protection systems for long distance cross-country lines. ICCP systems used on pipeline installations, such as this in Turkey, have monitoring stations at regular intervals along their length, which can be linked into a telemetry scheme allowing pipe condition to be checked from a central monitoring station.

Further details are available from BAC Corrosion Control Ltd. Tel: +44 (0) 1952 290321; Fax: +44 (0) 1952 290325; E-mail: bac@bacgroup.com Denmark: Tel: +45 70 26 89 00.