Towering over almost every coal mining pit in Australia is a goliath of mining equipment – the walking dragline excavator. They are one of the primary excavating machines used in open-cut operations throughout the Bowen Basin in Queensland and the Hunter region in NSW.
Open-cut mining is one of the most common methods of coal resource extraction in Australia and is carried out when the coal is close enough to the surface for the overburden to be economically removed by a dragline instead of using underground mining techniques.
According to Rod Baker, Motion Australia’s Business Development Manager for Mining in Queensland, a lot of engineering thought goes into the design improvement of draglines to optimise their performance in harsh operating conditions. Some of these machines are up to 50 years of age and can be kept into service due to modern day engineering and technology improvements.
“These are some of the largest mobile mining machines on the planet. While some heavy machinery like this will run on a track and roller system, draglines ‘walk’ and have a large-capacity bucket which is driven by wire ropes and electric motors. It drags back the earth to expose the coal, making it easier for miners to come in and extract it.”
Each of these draglines house numerous gearboxes and motors, he explains, the total number of which will depend on the machine’s overall size. This machinery is categorised into four main motion types – hoist, drag, swing, and propel. Spherical roller, cylindrical roller and tapered roller bearings are extensively used throughout the draglines.
The majority of bearings supplied for dragline applications come from Schaeffler’s FAG X-Life range, says Rod, which have had performance enhanced features added to the bearings to increase bearing life and increase machine availability by reducing the frequency of bearing replacement. Improvements are made to roller raceway finishes as well as to the length and diameter of rollers to achieve a greater dynamic and static capacity.
“Using generic products, a lot of dragline operators were changing their bearings around every five years,” he points out. “This would require major shutdowns and subsequent loss in production time. In conjunction with improved gearing quality and design, many dragline operators also opted to go for the enhanced Schaeffler bearings as well, so they could extend their maintenance shutdowns to seven, or in some cases beyond.”
When it comes to mining, environmental factors like dust, heat, water contamination and poor lube conditions shorten bearing life. Dragline gearbox bearings also have an extra challenge caused by the forward and reverse application in a dragline. The rollers in the bearings are subject to acceleration and deceleration which can cause skidding of the rollers as the shaft encounters change of direction. A unique Durotect black oxide coating is applied to the rollers and raceways to limit this skidding and extend bearing life. The black oxide coating also reduce fretting corrosion of the bearing mating surfaces on the shaft and in the housing bore.
“To date customers using this bearing technology in their draglines are happy to report a lower rate of bearing usage.” Rod says. “This is an impressive improvement and the reason why Motion and Schaeffler has garnered such a strong reputation amongst dragline operators. For many, it’s the gold standard bearing option across their entire dragline fleet.”
In his role within the mining sector, Rod is actively involved with many of Motion Australia’s customers, collaborating with them to seek out new opportunities for improving machine uptime. Whether it’s through improvements to offering the latest superior product or assisting with improving maintenance practices, he says it’s all about bridging the knowledge gap and helping the customer make informed decisions.
He also works alongside Schaeffler to implement online condition monitoring, which he says is a crucial aspect to keeping a complex piece of equipment – such as a dragline – moving.
“It’s something we’d like to do more within the industry, because where it has been implemented, the results are outstanding. Even the slightest anomaly concerning vibration, temperature, or sound can flag immediately in a digital system and end up saving huge amounts on breakdown costs, not to mention what can be saved in production downtime.”
Schaeffler’s ProCheck Online monitoring hardware is a compact and highly modular condition monitoring solution, designed for continuous, decentralised machine assessment. The system has the capability to incorporate a central dashboard which integrates wireless sensors as well as lubricators. The system’s presets can be easily configured to suit application specifics, but what really makes it stand out, enthuses Rod, is its versatility for mining and other industries.
“On a dragline, it can be situated on a gearbox to monitor the performance of parts, but these sensors are also applicable on motors, vacuum and fluid pumps, ventilators, fans, spindles and machine tools. Schaeffler is a world-leader in Industry 4.0 concepts, and Motion Australia’s close partner in the dragline and shovel market.”
The X-Life difference
Schaeffler’s FAG bearings are designed for ultra-high performance and the endurance required to operate in Australia’s harshest environments. The X-Life seal of quality ensures three key benefits: greater endurance, higher load capacity, and impressive flexibility.
These characteristics ensure longer intervals between required maintenance shutdowns, and significantly increased plant availability.