Modern Quarrying Q1 2019

its liners to about a year. “With our Barmac, we would previously change a rotor every week. We have since reduced it to twice a month. Techroq has since made some interesting improvements to this VSI crusher,” adds Mgxekwa. Safety excellence Safety and environmental care are non-negotiables at Eikenhof. Testimony to this are the recent high scores in both the Aspasa ISHE and About Face audits. In 2018, the oper- ation achieved a 93% ISHE audit, a significant improvement on the 87% achieved the previous year. Eikenhof also scored a remarkable 94% in its About Face environmental audit. Several interventions have made this possible and when we visited the site, Mgxekwa was very proud of the 700 LTI-free days on site. Several safety drills have improved the team’s safety awareness. Elsewhere, with safety in mind, the haul road design separates trucks going in different directions; one road is used by trucks going into the pit, and the other is used by loaded trucks going to tip. This forms part of the quarry’s compliance to the proximity detection system (PDS) legislation, which stipulates that operations have to do a risk assessment to determine their risk levels; if the risk is significant, they will have to install PDSs. As part of that process, Eikenhof is also currently conducting tests with two PDS suppliers for some areas where risk has been identified. As far as the environment is concerned, a major area of improvement has been around dust control on site. “We previously had some dust issues, which we have dealt with through the installation of a Dustcon dust control system. We also previously had an issue with vehicle oil spillage, which we have since rectified during 2018.” In conclusion, Mgxekwa reveals that the mine will soon expand westwards. When we visited the site, the team had gone seven benches deep, and the aim was to go four more benches deeper. “After that, the westwards mining expansion will start. The life of mine is a further 100 plus years,” concludes Mgxekwa. l

output of about 70 000 t of material on the ground per blast. Two Volvo 40 t excavators are deployed to load six Bell articulated haulers (3xB30D and 3xB25D units). Given that load and haul is one of the key cost drivers for any quarry operation, hauling distances from the pit to the crusher have been kept fairly short, with the furthest being 1,8 km (return trip). Meanwhile, haulers travel shorter distances when loaded, and a slightly longer distance when empty. This is a key factor in reducing fuel consumption. “When going to tip, the distance is about 600 m and 1,2 km when coming back to load,” explains Mgxekwa. The haulers tip directly into the primary Osborn 47x60 jaw crusher which is running at a gap of 120 mm. It is fed with run of mine material less than 600 mm. “From the jaw crusher we get 150 mm material which goes onto an intermediary stockpile (ISP). From the ISP, material is fed into a secondary 5 1/2 Simons cone crusher (Metso) running at a 38 mm gap,” explains Velapi Vilakazi, maintenance superintendent at Eikenhof. Fromhere, material is fed into a secondary Kawasaki (Cybas Cone) 1350Z crusher, before it goes into Barmac and Metso 48GD tertiary crushers. From the Barmac andMetso 48GD crushers, product will go into screen 3 and 4. The parallel screening process produces -5mm, 6,7mmand9,5mmsand. Any oversizematerial will go back to the Barmac and 48GD crushers. Both screen 5 and 7 produce 13,2mmstone. “If there is any further oversize material at screen 5, it is returned to the 48GD and Barmac tertiary crushers. Screen 6 produces 22 mm stone, and any bigger size at this screen becomes our 37 mm drainage material,” says Mgxekwa. As previously stated, the andersite rock wreaks havoc to both machinery and wearable components of the processing plant. The 5 1/2 Simons crusher has a liner change every three months and the Barmac rotor is changed twice a month. “We are very sceptical of changing our crusher liner suppliers. We trust Osborn, IMS Engineering and Metso in this regard,” explains Mgxekwa. The only crusher that doesn’t work very hard is the 48GD and it works

late last year, demand was at its peak, largely driven by asphalt and concrete producers. Much Asphalt is resident on site, while AfriSam’s readymix plant is also located on site. The two are the largest volume drivers for Eikenhof. “Of all our total sales, 35% go into our own readymix plant, which is located on site. Another 35% goes to road project- related customers such as JRA and Much Asphalt, while the rest goes to small customer groups such as lintel and tile manufacturers, as well as hardware suppliers,” says Mgxekwa. One of the key advantages of the type of material produced here is that it is used across several industries. This widens the quarry’s scope of supply. A key advantage of a wide customer base is that when one sector is down, another industry still drives demand. “The sales trend is favourable for us. Bear in mind that our business is affected by seasons – during winter, we see a reduction of sales to the road sector by 5-10%, while we see an upsurge in our sales to the readymix concrete sector during summer,” says Mgxekwa. Operational processes Several mining functions are out- sourced at Eikenhof, but contractor selection is thorough. Drilling and blasting is undertaken by renowned contractor, B&E (Basil Mining SA), while Alpha Plant is tasked with the load and haul function. An Atlas Copco T50 drill is deployed to drill in pit. Blasts are undertaken twice a month and are kept large with an

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QUARTER 1 - 2019 MODERN QUARRYING