Rudi Coetzee, Engineering Foreman, Modikwa

“The MTU Series 900s are relatively new engines, es-pecially in the South African market. They have been operating in Sandvik vehicles on Modikwa for two and a half years. In this time, they have outperformed oth-ers in their class.”

MTU engines power machines at Modikwa Platinum Mine on South Africa’s rich mineral reef

Underground mining demands extreme performance for extreme periods, both for miner and machine. In a 24/7 operation, durability and efficiency are the building blocks to profitability. At Modikwa Platinum Mine, one of South Africa’s leading platinum mines, you will find some machines which perform Herculean feats in places that they have very little right to be in. Up to 800m underground in the mine, drill rigs and load haul dumpers powered by MTU Series 900 engines, add significantly to Modikwa’s profitability through their performance, durability and efficiency. In terms of performance it means minimal downtime, fuel efficiency and low emissions.

Modikwa is located in South Africa‘s Limpopo Province, situated less than 120km from the world famous Kruger National Park. The region is rich in platinum reserves. Modikwa is a joint venture between African Rainbow Minerals and Anglo Platinum and forms part of the Bushveld Igneous Complex, spanning an area of 14,278ha. The Mine has been in operation since 2003 and plays a crucial socio-economic role with South Africa being the world’s largest producer of plati-num. It has 5,000 employees in total and contri-butes significant wealth to the country’s gross domestic product (GDP).

The mine is made up of two shafts, North and South; and is a 240,000t per month platinum production facility. Employing a hybrid mining technique where mechanised methods are used

for the main developments and the narrow, 60cm reef is conventionally stoped using a down-dip method. While excavation of the ore is done by conventional means, the mine employs trackless mining vehicles, which entails the use of tyre-dri-ven or mobile machinery underground as oppo-sed to using tracks as was prevalent in the past. This offers greater flexibility of the fleet as it is not constrained to one area or one level of the mine and machinery can move to and from pro-duction points much faster.

Machines with MTU Series 900 engines With its 6m long boom reaching to the face, drill rigs pierce the solid earth, punching holes appro-ximately 5cm wide; just enough to house and make way for the explosives. If the drill rig goes down, production slows. And in an operation that

Mining

Who: Modikwa Platinum Mine

What: MTU Series 900 engines for drill rigs and load haul dumpers to perform in the harshest conditions, at peak performance rates

Why: MTU Series 900 engines‘ ability to perform optimally with low fuel consumption, minimal downtime and with built-in automated features to enhance component forecasting

Where: Limpopo Province, South Africa

Africa South Africa

loses on average R10 million for each day that production stops, reliability and peak perfor-mance are non-negotiables. It is one of the only machines at Modikwa that stays underground, even as blasting takes place.

The three drill rigs on North and South shaft stay underground for a full week, being re-fuelled underground from containers delivered to it, when required. One drill rig is driven by a MTU type 4R 904 engine. Looking at the distances this machine has to drive underground — a one-way distance from decline to the face of up to 4.5km — the most impressive feature is the power

the engine delivers: rated power of 129kW at 2,200rpm. Rudi Coetzee, engineering foreman at Modikwa and responsible for all machinery on the North shaft, confirms this, “The MTU Series 900s are relatively new engines, especially in the South African market. They have been operating in Sandvik vehicles at Modikwa for two and a-half years. In this time, they have outperformed others in their class.” Sandvik South Africa has a performance service contract with Anglo Plati-num to service the machinery. This includes dump trucks and load haul dumpers (LHD) as well as drill rigs and roof bolters deployed under-ground, in the development of the mine.

Once the drill rig has finished its work, the face is charged up with explosives, and then blasted. After blasting, the LHD loads ore which is put into a dump truck and moved from the face to the conveyer belt. The conveyer belt takes the ore out to the plant. One of the dump truck ap-plications is powered by a MTU type 6R 926 C72 engine with rated power of 240kW at 2,200rpm. Being one of the smaller dump trucks on the mine, it more than makes up for its size in wor-kload. For this reason it is crucial that it remains working; for maximum periods, at maximum output. This is certainly evident at Modikwa, as Coetzee explains, “The MTU type 926 engine is performing at an excellent rate of approximately 210 to 240 hours of running time per month. The standard time is usually between 110 and 180 hours, which is also good. Certainly a great en-dorsement at an operation that, on average, ge-nerates up to R1 million an hour on these units.

Conditions above ground and underground for the enginesWith high temperatures and a healthy annual rainfall, the lush, subtropical conditions on the surface mask the harshness of the underground

environment. In this part of Limpopo the tempe-rature in summer is up to 42°C while in winter it plummets to an average of -2°C. During the rainy season, the area is known to receive in excess of 200mm of rain in a 24 hour period. Furthermore, 21 mines in operation in the area and another 16 planned for development, attests to the fact that it is one of the highest concentrations of light-ning strikes in South Africa. Everything that hap-pens underground is intense. Heavy machines manoeuvre through tight spaces. It is abrasive and combative. The sound is deafening, tempe-ratures reach in to the mid 40s°C — sustained by the heat that the hard-working engines pro-duce. Dust plays its part in challenging engine performance and in the newly developed areas it is flooding that is the major issue. Water mani-fests from underground due to seepage and a high water table.

Additionally, the drilling process produces water. It is not uncommon for an MTU service techni-cian to be working knee deep in water, while servicing a vehicle underground. “It is important that the MTU Series 900 engines operate no matter what conditions are experienced under-ground,” explains Coetzee. “The biggest challen-ge is the vast temperature range and the potential problems related to this.” Because the mine forms a closed loop system, cold ventilated air has to be physically pushed through the mine from the surface. Furthermore, burning as little fuel as possible and the after effect of releasing carbon monoxide, which needs to be pushed out of the mine by a fan is fundamental. “These chal-lenges are considered when selecting machinery and equipment to work underground,” says the engineering foreman.

Fuel consumption — low and efficientAutomated features on the MTU Series 900 en-

One drill rig is driven by a MTU type 4R 904 engine with rated power of 129 kW at 2,200 rpm.

The drill rig, with its long arms, punches holes into development ends where explosives are inserted and the face is blasted, opening up the ends for further production at Modikwa.

www.mtu-online.com July 2012

MTU Friedrichshafen GmbHA Rolls-Royce Power Systems Company

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MTU is a brand of Rolls-Royce Power Systems AG. MTU high-speed engines and propulsion systems provide power for marine, rail, power generation, oil and gas, agriculture, mining, construction and industrial, and defense applications. The portfolio is comprised of diesel engines with up to 10,000 kilowatts (kW) power output, gas engines up to 2,150 kW and gas turbines up to 35,320 kW. MTU also offers customized electronic monitoring and control systems for its engines and propulsion systems.

gines are what excite Coetzee the most, that is, the ability to have the engines think for them-selves underground. Asked what features they thought most significant in fuel efficiency, Coet-zee quickly states, “As the engines have the capability of decelerating themselves, this auto-matically results in improved fuel consumption. Additionally, if the correct amount of oil is not put into the engine, it just will not start.” Coet-zee sees the great benefit in the automated id-ling component. The engine can be set for a ten minute period of idling, for example, while wai-ting for the ore to generate. It depowers itself, cutting down the engine, using less diesel and pushing out less exhaust gas. “The less gas and heat they emit, the cooler the mine underground. Moreover, the low consumption rate keeps the cost per ton of material moved low at Modikwa, and that is crucial,” says Coetzee.

MTU automation systemThe engine control module (ECM) on both MTU type 904 and 926 engines enables the precise interaction between key engine systems. With the ability to extract and analyse crucial informa-tion, gathered from the engine over an extended period, engine lifecycle, engine performance, mine operating efficiency and a host of other areas are dramatically improved. The system prevents further deterioration that could result in major costs and quicker loss of the engine. It also improves planning, making sure that it does not impact the mining or production staff while making it easy to determine the service needed, resulting in a decrease of downtime for the ope-ration at Modikwa. Long-term stability of the engine functions to ensure that MTU engines remain as economical, clean and powerful over

their entire service lives as they are when new. This enables the system to compare the readings obtained from the sensors with the target set-tings for optimum engine performance.

This ensures that the engine is stable in terms of fuel consumption, emissions and performance over the entire lifespan, since the engine manage-ment system ensures that compensation is made for any changes resulting from wear and tear and environmental conditions. Thomas Phiri, Sandvik Contracts Manager, sees the benefits from a service point of view, “The ECM assists with fore-casting. We can predict when the engine is going to need maintenance, as well as indicating the services required, components to change, as well as new components needed in order to extend the life of the engine. From the history of operati-on on the machine my team sit down and plan what work needs to be done on the engine.” The-re is also a powerful protective element that en-sures the engine is not mistreated. The protection is provided in the form of sensors which indicate coolant temperature and engine temperature. If the temperature increases in an irregular manner, the ECM will raise an alarm, and if ignored the engine will de-rate to limp mode (reduced power), saving it from getting destroyed or harmed.

After sales serviceMTU works on a service exchange basis, estima-ting a down time of between eight and 24 hours for replacing an engine. If not planned correctly, the machine can stand for up to two weeks wai-ting for parts, at great costs. This is one of the reasons Coetzee is passionate about service and the impact good after sales service has on ma-king his job easier. “The single most important

criteria for selecting an engine or a machine group is after sales service. We must know from the company that we are dealing with that they are willing and able to help us 24/7, because we run all the time. We don’t stop for Christmas or New Year’s, it’s a 365 day production line. MTU was one of the few companies that could stand behind us and make people available for those times.”

Currently MTU is permanently on-site, with one representative per shaft, every day, Monday to Friday. This involves checking and maintaining the machines, downloading information and providing parts. Moreover, the MTU representa-tives are also on 24 hour stand-by. Phiri can therefore focus more time on other parts of his job, asserting that, “Because the MTU service technician is on-site to give us advice on the engine before major problems arise, it gives us an advantage. Having an arrangement with MTU assists Sandvik in minimising engine downtime and the cost of the machine. Furthermore, MTU transfers skills and knowledge to Sandvik ser-vice technicians and mine vehicle operators and artisans. From Sandvik’s perspective, this helps in keeping our client happy.”

When an engine goes down while underground at Modikwa, MTU is called and the problem must be rectified within a specified period. “Our target is always two hours in which that machine must be up and running,” says Phiri. Previously MTU technicians were called out from Johannesburg, 360km away. A localised MTU service point was set up in the little town of Burgersfort, 20km from the mine, improving their service and strengthening their commitment to Sandvik.

Thomas Phiri, Sandvik Contracts Manager

“Because the MTU service technician is on-site to give us advice on the engine before major problems arise, it gives us an advantage. Having an arrange-ment with MTU assists Sandvik in minimising engine downtime and the cost of the machine.”

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