The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region
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52 | ASIA Miner | Volume 13 • Issue 1 | 2016 Product News THE overland conveyor system at El Abra mine frst went into opera tion in June 1996. It is part of an exceptional project, the centerpiece of which is the CV-103 system, which incorporates a PHOENOCORD St 6800 steel cord conveyor belt 20,000 metres in length and 1600 mm in width. After 19 years of continuous service and 900 million tonnes of conveyed copper ore, the belt was fnally replaced. Its excep tional service life was made possible not least by the PHOENOTEC pro tection system and the special wear and abrasion resistant carrying and running side covers of the belt. Freeport-McMoran's and Codelco's El Abra mine is in northern Chile at an elevation of 4000 metres. Its porphyry copper deposits with sulphide and oxide mineralization deliver 8500 t/h of ag- gressive copper ore. After primary crushing, pieces have edges measuring as much as 300mm. They are taken to the ore stock- pile 9600 metres away by conveyor, traveling at about 6 m/s and covering an altitude difference of -510 metres. Because the belt conveys the ore downhill, its four 1800kW rotor motor drives gen- erate about 6000kW of electricity an hour, which is later used to process the ore. The brake discs measure 2500mm in diameter and are capable of halting the entire belt within 80 seconds in an emergency. The trough angle of the upper run is 40 degrees. A longer service life Produced in Germany, the PHOENOCORD St 6800 was designed for a ser vice life of at least 17 years. Realizing this ambitious goal involved a number of special measures: • A special notch and abrasion resistant rubber compound was devel oped for the belt covers, which also offers a high elonga- tion at break and high tensile strength. • The covers of the belt's carrying and running sides were equipped with PHOENOTEC synthetic single-cord transverse rein forcement – an additional wear protection system that dou- bles the belt's resistance to impact damage and ripping. The 1600mm-wide belt has 82 steel cords integrated into it. These measure 12.4 mm in diameter and give it a minimum break- ing strength of 6800 N/mm. The cover is 14mm thick on the carrying side and 10mm on the running side, bringing overall belt thickness to 36.4m m. Eleven years after going into operation and having conveyed 500 million tonnes of ore, the belt was found in 2007 to have lost no more than 2.7mm of thick ness to abrasion wear and just 1.4mm on average . After 19 years of continuous operation a section of belt was cut out and examined in detail and t he results are outstanding as seen in the graph. Given the belt's extremely rough, heavy, sharp-edged cargo and extreme climatic conditions in which it operates, a service life of 19 years is exceptional. Extreme conditions The belts were installed 19 years ago and operate in extremely challenging conditions: • At 3900 metres altitude, in air pressure of 600 hPa (compared with 1000 hPa at sea level). • In sandstorms with wind speeds of up to 150 km/h. • In an earthquake zone 2. • In daily temperature variations of 20 degrees C. To meet the tough demands of this project – ie producing splic- es with a service life which matches that of the belt and fatigue strength of 50% according to DIN 22110 standard – a robust, air-conditioned hall was set up. The splices, which measure al- most 6 metres in length, were produced in a four- step layout. Work was carried out in strict accordance with regulations and supported by state-of-the-art machinery and fresh splicing ma- terials. The result was a belt that ran perfectly from the word go. Test of endurance In late 1996 there was a major incident at the site in which two front-loaders pressed in on the system's tunnel causing it to col- lapse. This abruptly brought the belt to a standstill and the huge forces caused it to tear just behind the point of impact. The tear, however, was in the belt rather than one of the splices, as might have been ex pected. To ascertain that the incident had not caused further damage, a section of belt, including a splice, was cut from the most severely affected area and sent to Germany for testing. Exami nations revealed that in every parameter measured, it was still as good as new. The Institute for Transport and Automation Technology at the Uni- versity of Hannover tested the splice to DIN 22110 standard. This meant the fatigue strength of the trial belt, manufactured in factory con ditions in 1995, had successfully been reproduced by the splicing team in Chile. This outstanding result proved not only that the incident had had no impact on the belt, but also that the belt had been spliced with the same care and success in Chile as the frst test version. Incidentally, the replacement for the damaged section of belt Conveyor a star at El Abra By Bernd Küsel, executive vice president, Phoenix Conveyor Belt Sys tems GmbH The impressive overland conveyor system at the El Abra mine in Chile.