Metallurgical Coke and Calcined Petroleum Coke
NACE RP-05-72 stated “conductive backfill should be used to lower the total resistance of the ground bed, to improve current distribution, to prolong anode life and to provide a permeable medium for migration of gases…
Resistivity, Particle size, specific weight and chemical analysis are factors to be considered for backfill. Metallurgical coke and calcined petroleum coke are the two types used in cathodic protection.
Metallurgical Coke of high quality that gives optimum performance at a low cost is available in various size ranges.
| Fixed Carbon | ۸۶ – ۸۹ % |
| Moisture | ۰٫۶ – ۱٫۰ % |
| Ash | ۱۰ -۱۲ % |
| Volatiles | ۱٫۴ – ۱٫۸ % |
| Grading: 0-1mm; 1-5 mm; 2-7 mm; 3-10 mm | |
| Resistivity: 50 Ohm.cm | |
| Bulk density: approx. 700 kg/m3 | |
Calcined Petroleum Coke has been developed to meet all basic requirements for earth contact backfill. The carbon content, very high in calcined coke assures a low consumption rate of the backfill material and therefore a longer system life.
The low Resistivity of calcined coke and the small particle size allow the best possible contact between the anode and the surrounding soil.
Other advantages are, high specific gravity, round particle shape with high compression strength, wide range of particle sizes, various grades for loose and vibration fill and for pumping in deepwell application with enhanced wetting and lubricating properties.
| Fixed Carbon | ۹۸ – ۹۹ % |
| Moisture | ۰٫۱ – ۰٫۵ % |
| Ash | ۰٫۱ – ۰٫۸ % |
| Volatiles | ۰٫۶ – ۰٫۸ % |
| Grading: ۰٫۱ mm up to 5 mm | |
| Resistivity: 10 Ohm.cm | |
| Bulk density: approx. 800-900 kg/m3 | |
Handling
Conventional handling of impressed current backfills can be both time consuming and tiring for the installation operator. Deep well ground beds often require hundreds of sacks of backfill to be man handled into mixing tanks. Similarly shallow beds may require that the backfill is manually handled and spread along the ground bed trench.