How the latest high-performance components are helping mines and quarries improve productivity by reducing the time spent on machine maintenance
Despite the best efforts of plant and production engineers, many mines and quarries continue to operate far below their maximum potential capacity. For example, quarry and mine operators often run larger vehicle fleets than is necessary in the expectation that at least one vehicle will always be out of service for repair and maintenance, due to the aggressive nature of the working environment and conditions.
Furthermore, maintenance continues to represent a significant proportion of the overall operating costs in the mining and quarrying sector. In fact, the statistics are somewhat staggering, with market research indicating that the cost of machine maintenance in the sector can range from 20 per cent to a colossal 50 per cent of total costs – the highest ratio of all the manufacturing and heavy industries.
However, in these uncertain times, where the industry is faced with what looks set to be long-term uncertainty in the market price and demand for products, it is likely that this approach to operation will no longer be commercially viable. This fact, coupled with the rise in operating costs, means that mining and quarrying organisations are now increasingly looking to contain and reduce costs in order to sustain profitability, primarily through improvements in machine performance, reliability and efficiency.
In many instances, the key to achieving these goals lies not just in the performance of large systems such as engines and gearboxes, but also in the smaller components, including bearings and seals; for if these essential but frequently overlooked components fail to function then overall system failure and vehicle downtime is inevitable. Indeed, by paying attention to these vital parts, operators of mining and quarrying plant can realise significant cuts in operating and maintenance costs, while maximising equipment performance and life in service.
Having recognised this, component manufacturers are developing a new generation of parts specifically for use in the mining and quarrying industries that are virtually maintenance free and offer a far longer operating life under a wider range of demanding environmental conditions. The introduction of these dedicated technologies means that plant and maintenance engineers can now implement a range of devices that will help them to reduce maintenance costs, while improving machine reliability and overall plant productivity. Just as importantly, these new products can make considerable contributions to both health and safety, and environmental protection.
As these technologies cut the overall maintenance and repair demands they also eliminate the hazards that accompany them. This is particularly pertinent in the light of recent findings which indicated that 32 per cent of all mineworker injuries occur during machine maintenance and repair operations. Correspondingly, the increased safety means that the lost productivity and inflated health and insurance costs that come as a result of accidents can also be minimised.
For instance, oil injection mounting and dismounting tools enable engineers to safely mount and dismount bearings, couplings and other mechanical components without hammers, bars and torches, thereby reducing the risk of injuries that can come with the use of such tools. Laser alignment tools, on the other hand, help make motor and drive alignments safer due to the fact that engineers are no longer required to take manual measurements, eliminating the need for close contact with moving machinery.
As far as carbon footprints go, this new generation of components has been designed with environmental pressures in mind, helping mining and quarrying operations overcome the rising energy and waste disposal costs, while complying with the stringent government environmental standards.
Suitable for use on conveyors, crushers and screens, self-aligning bearings accommodate the axial thermal expansion and movements in bearings and housing arrangements commonly found in mining and quarrying equipment, thus achieving more consistent, reliable and efficient operating performance.
For example, a new bearing system from SKF has been designed to incorporate an SKF Explorer spherical roller bearing in the locating position and a CARB toroidal roller bearing in the non-locating position. The CARB bearing is a self-aligning radial bearing with an inner ring that moves independently of the outer ring, similar to a cylindrical roller bearing.
This construction allows the system to accommodate shaft elongation within the bearing without inducing internal axial loads, resulting in considerably less friction and lower operating temperatures. In addition, it operates with reduced vibration and noise levels and enables safer, more efficient designs. Ultimately, this leads to extended relubrication intervals and extended bearing service life.
In addition, as the radial clearance of the bearing is small and does not change during its operating life, it does not affect the long-term accuracy or repeatability of high-performance equipment. The CARB bearings are also packed with high-performance grease and sealed for life, allowing significant savings to be made in both the time and money spent on maintenance and repair.
Similarly, the latest high-performance seals are perhaps more effective than ever at providing protection against the intrinsically harsh operating environments of mining and quarrying applications, preventing system contamination resulting from the ingress of particulate matter and moisture. Furthermore, a correctly specified seal provides low levels of friction, retains the lubricant and essentially extends bearing service life.
Performance in harsh environments
There is a wide assortment of seals available on the market today, manufactured in various materials and designed to withstand both high and low operating temperatures, as well as resisting different chemicals. These include radial shaft seals, piston seals, mechanical seals and v-ring seals that offer exceptional reliability, minimal maintenance requirements and low maintenance costs. In addition, the SKF SPEEDI-SLEEVE has been designed to repair seal worn shafts, can be easily mounted onto worn shafts and provides an excellent matching surface for the seal.
Likewise, large diameter seals, such as the HDSF2 seals from SKF, feature a PTFE excluder lip, which is integrated within the body of the seal, to protect bearings from the ingress of abrasive dust and particles in a wide range of mining and quarrying applications. This enables the typical operating life of bearings in horizontal grinding mills, coal pulverisers and vertical rolling mills to be more than doubled, helping operators to improve productivity while reducing repair and maintenance costs.
While it is essential for the right components to be specified for an application, the correct installation and alignment of these parts is critical in order to realise the benefits of extended machinery operating life and improved plant reliability. Indeed, misaligned shafts are estimated to be responsible for up to half of all the costs related to rotating machinery breakdowns. However, to overcome this problem a new generation of laser shaft and belt alignment tools have been developed to offer quicker and more accurate results than traditional methods.
As an example, SKF’s shaft alignment TMEA series of instruments are easy to set up and use and allow for a simple three-stage process of measuring, aligning and documenting. They consist of two self-contained units, mounted opposite each other on the two shafts to be checked. Laser beams are transmitted from one to the other, with a handheld LCD display unit showing the actual alignment status. As adjustments are made, normally by inserting shims under the machinery feet, the display counts down to zero, indicating the correct alignment. The system also allows for documentation to be produced recording a machine’s condition over its working life and providing maintenance engineers with an essential tool for extending operating life still further.
To further ensure the optimum performance of mining and quarrying equipment over extended service lives, condition monitoring and predictive maintenance can also be used. One such system is SKF’s Copperhead programme which enables early detection of imbalances, mechanical looseness, bearing faults or high temperatures. This allows remedial action to be taken before performance is degraded, and so eliminating downtime. Furthermore, a range of handheld analysers are available for simple analysis and reporting.
Above all, what is needed is a combination of high-performance components and a preventative approach to maintenance if mining and quarry companies are to maximise output at the lowest possible cost. By adopting these technologies, reliability and uptime can be optimised, health and safety improved and environmental impact minimised, leading to increased plant productivity and, ultimately, better returns and profitability.
For further information, visit the website at www.skf.co.uk.