Vol 7, No 3 (2016) > Metalurgy and Material Engineering >

Case Study for Upgrading the Design of Impressed Current Cathodic Protection for Tank Bottoms as an External Corrosion Control Method

Kemal Gibran, Andi Rustandi

 

Abstract: Engineering
design calculations for tank bottom sections, including direct
current requirements and voltage calculations, followed by additional
structures, such as electrical
grounding systems, have already been successfully implemented and
controlled in field conditions. Furthermore, the effect of soil
resistivity in layers, oxygen content and the pH value of the soil against the disproportionate IR-Drop voltage, including its effect on potential distribution, have been already successfully observed. Other influences, such as the depth and location of the anode groundbed
determination along with the establishment of impressed current cathodic
protection related to the main tools and equipment, such as external corrosion
control methods, have been defined as the most effective ways in order to control
potential distribution against the additional structures. Persuant to the verification results from the site located at Marangkayu, East Borneo, it has been determined that high soil resistivity could cause error readings in
accordance with the accumulation results of the true readings and the IR-Drop
voltage, since under real conditions, the tank structure would have received
less current flow from an anode compared to a lower result. Naturally, a low pH
value from the soil would decrease soil resistivity and enhance potential
distribution from the anodes to the tank structures. The results show that the cathodic protection required 10 additional
anodes, (each one is of a tubular mixed
metal oxide
) with a DC
supply at minimum
amperage of 154 Amps and a
minimum voltage supply of 32
Volts. During the research, it was identified that high soil resistivity above 3000
ohm-cm
would cause error readings. Naturally, acidic soil is in
the region of pH 5-7 value, which would
decrease soil resistivity and enhance the potential distribution from the anode to the tank structure.
Keywords: Aboveground storage tank; Engineering design; Impressed current cathodic protection; Potential mapping; Voltage drop

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References


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