Document1 2/9/08 4:45 pm Page 1 DRIVES AND CONTROLS DRIVING FORCE Siemens fitted the first Bucyrus 8750 with the new drive system for use in Shuenhua Group’s Zhungeer mine,120 km south of Hohhot, the capital of the Nei Monggol Province (Inner Mongolia) With today’s high energy costs, it is especially important to choose the right equipment to drive and control mining machines – John Chadwick considers some of the latest technology offerings U ntil now, draglines all over the world were equipped with geared drive systems motors only. But now Siemens and Bucyrus have jointly developed a gearless AC drive system – Simine DRAG. One of the first such systems is in China’s Zhungeer coal mine, but draglines already in use can also be retrofitted. The drive systems with a performance of 9.7 MW are used for the hoist and drag motions. By eliminating the gears, maintenance and operating costs are reduced in comparison to conventional drives. The extended service intervals reduce maintenance and increase the excavator’s availability. Gearless AC drive systems also offer up to 20% more efficiency and use less energy, thus reducing operating costs. Simine DRAG combines reliable electronics and controls proven in thousands of Siemenspowered locomotives and mining shovels, with gearless ring motors that have been in reliable service in grinding mills, mine hoists, chain excavators and conveyors for more than 25 years. Siemens combined these proven, reliable components into this new, revolutionary dragline drive system. The dragline’s ring motors are fitted with nine winding systems. The ring motors were delivered in two halves and had to be assembled on-site. The assembly was especially difficult as 90% of the work had to be done outdoors. The roof was added later and all hoisting jobs had to be carried out by mobile crane. Bad weather conditions and coal dust from the mine nearby further impaired the work. Sandstorms occurred almost every day and heavy winds made assembling the poles difficult. “Testing was done sometimes under extreme conditions. Aside from some starting problems, the unit has proven to be very successful. A top result for a new technology!” explains project director Ralf Lechtenfeld. AC IGBT inverters supplied and installed by Siemens Energy & Automation in Atlanta control the drives. The excavator has been in operation since December 2007. To achieve high uptime and short MTTR (Mean Time To Repair), Siemens offers what it claims is “the most advanced and user-friendly maintenance computer in the industry. It shows the mine electrician where the problem is, and which part is needed to fix it. The dragline system also seamlessly integrates with Siras and Midas. Siras remote diagnostics uses Internet technology to keep the factory on the machine.” Siemens and Bucyrus service technicians and other experts can log on from around the world and can do the same work as the electrician on board the dragline, with the exception of tightening a screw. Midas harvests a wealth of data during normal operation and makes it available for productivity analysis and optimisation. Turning to electric shovels, Boris Rathmann of ABB Automation explains the latest in shovel drives from ABB. “Since 1999, the Center of Excellence Open Pit Mining of ABB Automation Cottbus has steadily expanded its position in the market for discontinuous open SEPTEMBER 2008 International Mining 91 Document1 2/9/08 4:47 pm Page 1 DRIVES AND CONTROLS P&H Mining Equipment, a global leader in the manufacture of electric mining shovels, is the most important partner for the supply of ABB Drives for Mining. P&H uses AC drive Technology for the 4100 Boss shovel in an oil sand mine and was able to increase the productivity (payload) with highest availability pit technology. ABB has delivered completely new drive systems for 15 electric rope shovels and two draglines. The experience from this successful project forms a solid base for further expansion in this market segment.” Adverse conditions for open pit machines, such as dust, extreme temperature fluctuations, heavy shock and vibration loads require a special design for state-of-the-art power electronics. The new ABB frequency converter ACS800 had to prove its worthiness. Based on vibration measurements from various open pit mining machines and subsequent simulation calculations, the control system was tried and tested for its suitability under these strenuous conditions. The results were used to mechanically reinforce the design of the converter switchgear. Concluding test lab examinations proved that ABB Drives for mining meet the high demands of open pit mining in terms of shock and vibration resistance. The excellent communication between the ABB companies in Germany, Brazil and Israel yielded extremely short installation and commissioning times at consistently high quality. The follow-up order for a second excavator in the same Brazilian mine proves the high customer satisfaction. During ongoing projects e.g. in Israel, the ABB drive system’s electrical concept could be further enhanced. Unlike the previously used system, a new regenerative supply unit (AFE Active Front End) recirculates power to the mains generated by the drives during shovel 92 International Mining SEPTEMBER 2008 operation. Only three months after commissioning, this new concept could save 23% of the energy expenditure – significantly more than initially expected. Dietmar Simke of the same company notes that “in spite of more and more common use of variable frequency controlled drives in open pits, drives with slip-ring motors still represent a broadly used technical solution. ABB Automation [and predecessor companies] has integrated more than 2,000 slip-ring motor drives for overburden conveyor bridges, bucket wheel excavators, bucket chain excavators, spreaders and belt conveyors from 1970 until now.” ABB Automation took up the well known idea of using power electronic components to control the starting process of slip-ring motors in order to achieve better control and reliability of drive systems with slip-ring motors currently in use or to be built in the future. The starter consists of a six-pulse rectifier with downstream pulse-width controlled single resistor chopper. A rotor resistor selectively and continuously influences the torque generated by the motor. As in circuits with liquid starters or staged resistor starters, the motor current which can be measured easily, will be used to control motor torque. Depending on the drive system requirements simple or more complicated starting procedures can be applied. In detail that may be: ■ Motor-start with constant or defined changing motor torque, independent from load torque ■ Time scheduled motor-start, independent from load torque ■ Speed controlled motor-start with variable speed set point ■ Combination of these procedures and special starting procedures (heavy duty starting service) ■ The possibility of taking targeted influence to the torque generation in drive systems with DC injection breaking. In all cases one has to consider the limited control range to the minimal generated motor torque, caused by the dimensioning of the resistor. The driving forces for the development of an electronic starter included: ■ Improved possibility for well defined start up behaviour ■ Reduce maintenance by replacing the heavily wearing step contactors for staged resistors through an electronic circuit ■ Safe forecast of the availability of the starter resistor for further starting procedures by improving the temperature measurement of the single resistor. Moventas Santasalo supplies customized heavy duty mechanical drive solutions for mining and mineral applications as well as start-up and customer support services labeled Figure 1: Principle circuit of an ECOSS electronic compact starter for slip-ring rotor drives Document1 2/9/08 4:58 pm Page 1 DRIVES AND CONTROLS with the Santasalo trademark. The company specialises in the design and manufacture of large diameter multisegmented ring gears used to rotate large drums, kilns and mills. The company is the original equipment manufacturer for the multi-segmented ring gear concept for mineral industry applications. In addition to large Santasalo spur multisegmented ring gears, Moventas is now also able to offer helical multi-segmented ring gears. Moventas Santasalo says its “helical multi-segmented ring gears run smoothly and quietly, offering a refinement over spur gears in certain applications. Developed to meet individual needs, Moventas can deliver the best solution with helical or spur ring gears for both new installations and replacements.” The multiple segment design of Moventas ring gears enables higher precision machining with more accurate tooth geometry for diameters of 3 m and up, no upper limit exists. Pioneered by Santasalo, today part of the Moventas Group, multi-segmented ring gears have been designed and manufactured in Finland for over 30 years. With more than 500 operating worldwide, the design has proven durable and reliable. Moventas Santasalo’s multi-segmented ring gear consists of 10 to 20 segments bolted together to make immensely strong and precise large diameter gears. The length and number of segments depends on gear diameter and is optimised for each application. The result is a significant reduction in lead-times as well as easier and less costly transportation compared to single piece castings. Assembly is also simplified, with the compact segments being easier to lift and position. The ring gear and pinions are usually delivered with the main gear units including auxiliary drives and bedplates. Since Moventas can supply the complete package, straightforward and trouble-free installation is assured, leading to faster start-up and optimal running. Gear wear is minimised by using Austempered Ductile Iron (ADI) in gear castings. ADI has the high strength to weight ratio required together with high resistance to fatigue and wear for long ring gear life. Highly accurate production and assembly techniques minimise vibration and further enhance the long service life of the gear. Condition monitoring tools enable the performance of a drive to be followed either in real-time or as a part of regular inspections. Should damage to a gear occur, individual segments could be 94 International Mining SEPTEMBER 2008 Moventas Santasalo's multi-segmented ring gear replaced instead of changing the whole gear. This makes it possible to carry spare parts for critical applications if required. The reliable, trouble free operation of Santasalo multisegmented ring gear packages is supported throughout their life-cycle by a comprehensive range of services, with a strong focus on condition management and proactive maintenance. Bonfiglioli is custom-engineering new combination drives for materials handling and mining applications, which demand high levels of cost-efficient power from compact installations. One recent combination employs a Trasmital planetary drive coupled with Bonfiglioli’s new generation heavy duty HDO/HDP helical series to produce an apron feeder drive that offers the best features of each. Bonfiglioli’s modular Trasmital 300 multipurpose planetary drives – known for their torque density and compact dimensions – can be coupled with HDP Parallel Shaft and HDO Bevel Helical units in sizes up to 72,000 Nm to produce outstanding reliability and torque densities to record values, says Bonfiglioli Transmission (Australia)’s Managing Director Malcolm Lewis. “Such combinations produce powerful high torque drive combinations especially suitable for low speed applications. The power of such combinations will be further extended this year with two new HDO/HDP sizes to be released that will bring the torque capacity of the range up to an impressive 140,000 Nm,” he says. “The versatile HDO/HDP drives combine brilliantly with the 100% modular Trasmital 300 series of multipurpose planetary gearboxes, which is available in 14 basic sizes, with output torque up to 540,000 Nm and transmissible power up to 450 kW.” The Trasmital 300 series gearboxes - which can also be combined with Bonfiglioli’s C1, A and F helical gearboxes - are especially suitable for applications requiring high reduction ratios, high transmissible torque and high radial loads on output shafts. The Transmital 300/HDO combination gearmotor being used in an apron feeder application Document1 2/9/08 4:59 pm Page 1 DRIVES AND CONTROLS combination drives, tailored to customer requirements, feature excellent torque distribution across their entire ratio range of the HDO/HDP drives. Their gear ratios are laid out in close progression and the drives having a rugged capacity to cope with the shock and impact of intermittent loads. At AIMEX, Danfoss displayed its new VLT family of AC drives. The drives range in capacity from 0.18 kW to 1.2 MW and are highly efficient, with 98% of the power being transferred to the motor. Even this small percentage can mean significant heat loss on a large drive, but this is managed by transmitting 85% of the excess heat through the backchannel heat sink, removing it from the drive, panel and working environment. Feature of the VLT drives that minimise installation space include built-in DC coils for harmonic suppression (rather than external AC-coils), built-in RFI filters, and the optional placing of input fuses and the mains disconnect switch within the standard enclosures. Standard enclosures sizes are available with an IP21 (NEMA 1) or IP54 (NEMA 12) rating. Time savings in installation, commissioning and maintenance of the VLT drives are provided by an intuitive user interface using an award-winning control panel, a single drive type for the full power range, a modular design than allows fast installation of options, automatic tuning of PI controllers and virtually maintenance-free operation through robust design and efficient monitoring. Turbo couplings Voith says type TPKL turbo couplings “are extremely robust and provide high availability, which has contributed to increased production in many mines. References span the globe from Australia and South Africa to Spitzbergen and the USA. To meet special customer Weighing in at nearly 65,000 kg this girth gear set a new record at David Brown Gear Industries in South Africa. This was an order worth $1.3 million from F L Smidth Minerals for a project in Armenia. The single helical SAG mill girth gear which is cast in four pieces has 362 teeth, 0.75 DP, 863.6 mm face width, 12.4 m outside diameter and a 10.5 m diameter bore. It is manufactured from steel with a hardness range of 269/321 BHN and the gear teeth are cut to AGMA grade 10. David Brown is also supplying three mill Flotation Cell Drives Drum Drives Crusher Drives Agitator Drives Rolling Mill Drives Conveyor Drives Coiler Drives Drum Drives Power Player in Mining and Metallurgy Complete drive packages for worldwide projects throughout the industry Full service support KUMERA POWER TRANSMISSION GROUP Kumera Drives Oy, Finland Kumera Antriebstechnik GmbH, Austria Kumera AS, Norway Kumera Shanghai Representative Office, China 96 International Mining SEPTEMBER 2008 Document1 2/9/08 5:00 pm Page 1 requirements, Voith Turbo offers versions with reduced height and an external tank, to enable use on a wide range of foundations and base frames. Space and adaptability play a crucial role, particularly when it comes to retrofit solutions.” Voith’s TPKL family of fill controlled turbo couplings has a new addition, the new, alignment free version (TPKL-T). This is a response to demand from users. Since its introduction to the market in 1998, TPKL couplings have a proven history of performance and reliability. TPKL-T fill controlled turbo couplings are fed by an external oil supply system. The oil supply system is located near the drive assembly and uses several flexible hydraulic hoses for easy assembly and connection to the TPKL-T housing and oil cooler. This allows optimum placement of the oil supply system and associated electrical components. The result is good accessibility around the drive. The actual drive, made up of the motor, Voith TPKL-T turbo coupling and gearbox, is centrally supported by a standard torque-arm support below the drive. This means that not only the coupling, but also the entire drive can easily be attached to and detached from the drive pulley on site. The first 12 drives with this new ‘tunnel design’ are being installed in a mine in Pennsylvania, USA, which produces in excess of 10 Mt of coal. A follow-up contract for a further 32 Voith TPKL-T turbo couplings has already been agreed; the mine wants to use the tunnel design as standard on all new belt drives. Meanwhile, other mines have expressed interest in the benefits of the Voith TPKL-T and are considering this drive design for future conveying requirements. The successful basic TPKL turbo coupling was specially developed as a compact drive solution for belt conveyors and has been used on every continent since its launch. The TPKL series has been installed in over 250 drives with a power range up to 250 kW @ 1,500 rpm or up to 430 kW @ 1,800 rpm. In addition, over 150 drives are in operation with a power range of up to 500 kW @ 1,500 rpm or 860 kW @ 1,800 rpm. Since launch, the series has been supplemented to enable Voith turbo couplings featuring fill control technology to be used on belt conveyors with an individual drive power of 2,400 kW (1,200 rpm) or 4,700 kW (1,500 rpm). Baldor Electric, manufacturer of energy saving industrial electric motors, drives, power transmission products and generators, has introduced the new Dodge MagnaGear XTR. This extra tough reducer has been engineered to offer maximum reliability and superior performance in tough, high torque applications. The MagnaGear XTR is available with parallel shaft or right angle configurations and will initially offer torque capacities up to 104,000 Nm (920,000 lb-in). The modular design of the product allows for multiple mounting configurations and can be used with a variety of soft start mechanisms, making it ideal for a variety of conveying applications. Designed to meet or exceed AGMA and international standards, this heavy duty, cast iron product features gearing that is carburised, hardened, and precision ground. Tandem HBNR lip seals are standard for extra protection, all bearings exceed AGMA standards for L10 life, and all components are power matched for optimum performance at a lower installed cost. In sizes over 44,060 Nm (390,000 lb-in), the MagnaGear XTR features the proven Dodge planetary design, providing a compact, durable, light weight and economic solution for high torque applications. A complete line of engineered accessories are available including, internal lift-off style backstops, cooling systems, rigid couplings, torque arms, swing base mounts, tunnel housings and baseplates. Brevini’s Posiplan is a new range of ultra-compact planetary and bevel helical gearboxes for industrial applications. These new gear reducers, protected by a specific patent, feature a combination of planetary and helical/bevel gears that takes advantage of the strengths of each SEPTEMBER 2008 International Mining 97 Document1 2/9/08 5:00 pm Page 1 DRIVES AND CONTROLS Voith's TPKL family of fill controlled turbo couplings has a new addition - the alignment free version (TPKL-T) technology: compact size, reliability and easy maintenance. Designed primarily for shaft mounting, ultra-compact gearboxes optimise characteristics suitable for this type of application, which is extensively used in a wide variety of sectors. In mining this would be, for example, in washing systems, drying furnaces, certain crushers, belt conveyors, bucket conveyors and more. Proportional directional control valves by Brevini Hydraulics, with inlet flows of 140 and 240 litres/min are used for a wide range of applications such as drilling machines. All the components of the valves are exclusively designed by the company, which holds four internationally recognised patents. The new AquaMaKKs water cooled clutches and brakes from Wichita Clutch are air, hydraulic, 98 International Mining SEPTEMBER 2008 or spring set actuated, featuring copper wear plates optimised for heavy-duty continuous slip tension applications. AquaMaKKs™ consist of a series of alternating friction discs and water jackets. Torque is transmitted by applying axial force from the pneumatic, hydraulic, or spring set actuator. Copper wear plates provide excellent heat dissipation. Simplicity of design with fewer parts simplifies installation and maintainability, saving both time and money. Shim design makes it easy to maintain and adjust for wear. A unique patent pending water jacket design ensures high heat absorption and torque stability, allowing for greater heat dissipation over similar sized competitive units. Unique mounting pattern enables direct replacement to Wichita or competitors’ units, requiring no design changes for the customer. Ameridrives Couplings’ TorqueSentry is a torque limiting coupling. Its main purpose is to avoid catastrophic failure or destruction in the case of overload of the driveline, which can result in injuries or unexpected and expensive downtime of the entire system. The design offers several distinctive features that include immediate and precise point of release, adjustable release torque, selected release torque remains constant and is not susceptible to fatigue, back-lash free power transmission and minimal maintenance requirements. The principle of the TorqueSentry is very simple, but highly effective. A pair of tapered pressure rings is forced over a tapered sleeve by oil under pressure. The pressure ring is then locked in place by mechanical fuse pins. This Document1 2/9/08 5:02 pm Page 1 The new Dodge MagnaGear XTR produces a friction connection between a sleeve and a shaft. At overload, the coupling instantaneously releases the fuse pins and interrupts the drive. Avtron’s AV850 SMARTach II heavy mill duty modular magnetic encoders fit standard 216 mm FC-Face motors. Other models, from 115 to 318 mm are available to fit other motor sizes. The AV850 is designed to eliminate encoder failures. All AV850 electronics are fully encapsulated with no moving wearing parts. Avtron reports that AV850 sensors locate over four times “farther from the rotor than the competition; no more sensor/rotor grinding! The AV850’s high-power outputs have over 50 times more capacity. Miswiring an encoder is common – and it shouldn’t cost you time or money. The AV850 has full output short circuit and reverse voltage protection, plus surge protection.” AV850 SMARTach II sensors digitally selftune the outputs to eliminate drive trips caused by poor encoder signals. AV850 sensors feature great diagnostics. If the encoder signal is not ideal, the alarm output and LED inform the machine operator that the encoder should be checked, before a failure occurs! The AV850 even checks the rotor position before running starts. Stopping overheating WEG has developed an innovative solution to the problems of overheating in AC induction motors at slow running speeds under frequency converter/variable speed drive control. Termed Optimal Flux™ Technology (OFT), the WEG solution eliminates the cost and size penalties of some manufacturers and maintains the reliability and life of the motor by limiting any temperature rise at low speeds. Using the OFT solution for variable frequency drives allows WEG to team its standard off-theshelf Totally Enclosed Fan Cooled (TEFC) NEMA Premium Efficiency, NEMA High Efficiency and IEC Premium Efficiency EFF1 induction motors as an option with the CFW-09 and CFW-11 drives. This enables the motors to run at least 11% cooler over the entire speed range than traditional constant flux strategies offered by other manufacturers. Typical applications include positive displacement pumps, compressors and conveyors. Sebastião Lauro Nau, WEG Motors R&D Manager commented: “Typically each 10°C reduction in operating temperature doubles the life of an induction motor, so WEG can offer a three-year extended warranty, with less maintenance costs and down time. Use of standard motors and spares also reduces the cost of spares and enables the motor to be used in a wider number of applications on a site.” With all these benefits, the WEG NEMA Premium / Optimal Flux CFW-09 Variable Frequency Converter combination costs around 10% less than competing inverter class drive solutions, while lasting longer and saving space. Variable speed converter drives were developed in the 1990s and enabled the reliable, low maintenance TEFC AC induction motor to replace DC motors in applications where speed variation was required to match application and improve energy efficiency over constant motor speed operation. However, the problems of overheating arise stop wasting money! Vacon variable speed AC drives are a perfect companion to control your AC motors. They improve process control and save energy. Vacon Liquid-Cooled AC drives reduce the operating and maintenance costs of your plant. See www.vacon.com for more information. www.vacon.com SEPTEMBER 2008 International Mining 99 Document2 2/9/08 1:27 pm Page 1 DRIVES AND CONTROLS Testing hydraulic motors at Hägglunds Drives' new, large hydraulic laboratory Hydraulic research when TEFC induction motors are operated at slow speeds but are still required to provide a constant torque for industrial applications such as compressors and conveyor belts. As the motor speed decreases, the ventilation provided by the shaft mounted cooling fan also decreases because the fan speed is reduced. Manufacturers offered different solutions to the problem, which increased the cost, increased the motor dimensions, increased the nominal power output or reduced the efficiency and increased the energy consumption; frequently a combination of these penalties occurred. The solutions included external fan installations for forced ventilation and overpowered/oversized motors to reduce the temperature rise effects. Sebastião Nau continued: “There are three major types of loss which contribute to temperature rise in TEFC induction motors under variable speed constant torque conditions. These may be summarised as the iron losses (hysteresis and eddy current), Joule effect losses from the flow of current in the stator and rotor bars and the mechanical losses from the friction of rotation of the fan itself.” If the temperature rise exceeds the motor’s insulation thermal class, the motor had to be derated or it would fail. A 10°C rise in motor operating temperature halves an induction motor’s useful service life. WEG’s patented innovations in insulation coating technology – WISE - were employed to enhance insulation service lifetime, but the problem has, up to very recently, proved difficult to solve to maintain motor efficiency. The physical law governing induction (Faraday/ Lenz law) dictates that the magnetic flux in a motor is directly proportional to the ratio of electromotive force (V) applied to the motor and the frequency (f) of the source of the electromotive power. By reducing the 100 International Mining SEPTEMBER 2008 frequency to reduce motor speed and reducing the current to keep the flux constant (V/f ratio), this was an effective and simple way of maintaining constant torque. Many motor manufacturers adopted this control strategy. WEG technologists found that the conventional control strategy had overlooked an important variable. This variable is that, at each operating speed, there is an Optimal Flux™, which minimises the motor losses while keeping the torque constant. By calculating the Optimal Flux for every operating speed, and programming the frequency converter to change the flux to the Optimal Flux at every speed point, the motor losses were minimised over the entire operating speed range. WEG’s theoretical modelling of the benefits of OFT was confirmed by actual trials covering NEMA High Efficiency, NEMA Premium Efficiency and IEC Premium Efficiency EFF1 motors from 3.7kW to 110kW; the match between the modelling and actual performance under carefully monitored conditions was close. Sebastião Nau concluded: “A comprehensive performance trial was set up against four major competitors using 3 kW, four-pole 1,800 rpm motors, over a 1000:1 speed operating range. This, in its turn, clearly showed that WEG’s Optimal Flux Technology strategy for WEG NEMA Premium Efficiency, NEMA High Efficiency and IEC Premium Efficiency EFF1 motors and motor/CFW-09 drive combination ran significantly cooler than its competitors. Optimal Flux technology is also a feature of WEG’s newly launched CFW11 frequency inverter series. In implementing this OFT control strategy for its highest efficiency TEFC AC induction motors, WEG offers users high reliability and a long, low cost life. One of the world’s largest hydraulic laboratories is now up and running at Hägglunds Drives’ head office in Mellansel. It covers 1,500 m2 and has a total installed hydraulic power capacity of 5.5 MW in its 11 test cells. “To assure the consistent high quality of our products, we need access to a modern laboratory where we can test all our hydraulic motors, accessories and complete systems at an early stage,” explains laboratory manager Anders Westerlund. “This investment is an important part of our continuous development for better and improved products and drive systems. Our vision is to improve the productivity for our customers by using the performance in our hydraulic drive systems, and with this extension of the hydraulic laboratory we will be able to improve the performance even further." says CEO Per Nordgren. Hägglunds Drives has just been sold to the German company Bosch Rexroth. “Together with Bosch Rexroth we will be able to further develop our focus on offering complete hydraulic drive systems in several of our existing segments. We will also be able to offer our deliveries of complete hydraulic drive systems to new interesting segments as renewable energy production. Combined with Bosch Rexroth’s strong position on specific markets where we’re not represented today we will have a good position for continued strong growth, says Nordgren. Sensor support Hansford Sensors has launched a new range of ATEX and IEC Ex certified, intrinsically safe vibration sensors with 4-20 mA outputs, ideal for direct use with PLC, BMS or other 4-20 mA input modules. The low cost HS-420I and HS422I sensors are designed for use in online vibration monitoring applications where the environment contains inflammable gases, fumes, chemicals, powders, dust etc. The new models will allow maintenance engineers to monitor vibration levels of pumps, fans, compressors, motors, conveyors, drill rigs and all types of rotating machinery, which are in a potentially explosive working environment. The new HS-420I series of sensors are sealed to a minimum of IP67 and can be used in both Group I (Mining) and Group II (Petrochemical) applications. With their construction in stainless steel and ability to withstand tough operating conditions, the sensors offer reliability, optimum performance and long service. IM Document2 2/9/08 1:28 pm Page 1 DRIVES AND CONTROLS Condition monitoring Shaun Skilton* explains how a proactive approach to condition monitoring can considerably reduce the cost of oils and lubricants T he old saying about “oiling the wheels of industry” has always had something of a double-edged meaning to it. When used by people from the political or economic arenas, it all too often implies that injections of cash can solve almost any problem. Those involved in the actual oiling of industry’s wheels and machinery, however, know better. Maintenance engineers in mining and processing, are accustomed to having to operate under increasing pressure to keep equipment operational. They accept their role is more about saving money than spending it, and limited budgets have to be used as cost-efficiently as possible to help control overall running costs. One area where more efficient maintenance procedures can pay dividends in maintaining in optimum condition the hydraulic oils and lubricants that help keep a mine’s machinery and equipment in full working order. It has been estimated that across industry over 85% of hydraulic system failures can be directly attributed to contamination of the hydraulic fluid. Oil lubricants in rotating machinery can also degrade as a consequence of contamination with particles and moisture. Although the aggressive environments found in mining might be a contributory factor in oil contamination, the problems of moisture ingress via faulty seals and gaskets, and contamination with metallic particles from rotating surfaces and bearing wear, have been common across industry for years. As these problems build up gradually, they inevitably increase operating costs as loss of lubrication leads to higher levels of wear in bearings and shafts, with increased power and fuel consumption. Water ingress into oil can result in bacterial and fungal growth that affects its properties and produces damaging acid corrosion and oxidation of bearing surfaces and rubber seals. The earliest solution to these long-term problems used to be simple reactive maintenance; when contaminant build-up brought the system to a grinding halt, the oil was changed and, inevitably, repairs were carried out on the equipment. Anathema to today’s maintenance engineers, this crude and expensive approach was soon replaced by proactive maintenance, in which oils and lubricants would be changed on a more or less rigidly controlled schedule of programmed maintenance. While this methodology is better at minimising equipment downtime, it can prove wasteful if contamination has not yet reached damaging levels. And replacement with new oils and disposal of the old by approved contractors is an increasingly costly option. Rather than replace oils and lubricants, current thinking now revolves around predictive maintenance, with the goal of extending an oil’s operating life by use of relatively low cost condition monitoring equipment, allied to a more practical approach to the replacement of filter elements. Unlike the expensive systems needed to monitor the performance of capital equipment such as high-speed generators and compressors, with their accelerometers and vibration analysis tools, oil condition monitoring involves simply the detection of particles and moisture. These are tasks that can be performed quickly and accurately, with a range of instruments suitable for either off-line testing or fully integrated into the oil lines to give a continuous indication of the oil’s condition. Solid particle detection by instruments such as Parker’s LaserCM and the new IcountPD generally involves a laser-based operation in which a beam of light is passed through the oil. As particles pass the photo diode sampling point, the reduction in light intensity transmitted, which is proportional to the particle size, is measured and recorded. Data can then be downloaded into trend analysis software that enables quite subtle deteriorating changes in a fluid’s condition to be picked up and acted upon before any abnormal wear becomes a problem. Although they can be connected dynamically in-line, instruments like the LaserCM and Parker’s H2Oil water-in-oil monitor are essentially portable instruments complete with handheld data capture and LCD display units. With test cycle times as little as two minutes, these lend themselves to predictive maintenance programs. The IcountPD particle detector, on the other hand, is designed to be integrated into the oil lines as a permanent, intelligent device that gives a continuous indication of the oil’s condition. Another laser diode based instrument, this small, low cost unit can be built into equipment by OEMs, or easily retrofitted in the same way as other in-line instruments. Immediate display of oil condition is via a simple LED readout giving a continuous indication of particle and moisture content, with early warning indicators for Low, Medium or High contamination levels. The moisture sensor, with a reporting range between 5% and 100% saturation, is an option that can be included in the initial specification. The particle display parameters conform to the ISO 4406:1999 method for coding the level of contamination of hydraulic fluids by solid particles. In addition to its integral display unit, the IcountPD features full communications capability with RS232, 0-5V and 4-20mA AND CANBUS J1939 outputs, opening up the possibility of remote, even off-site, condition monitoring of oil and hydraulic systems. Solid particle detection by instruments such as Parker's new IcountPD generally involves a laser-based operation in which a beam of light is passed through the oil Compared with the proactive maintenance approach of testing oils according to a preordained schedule, these instruments all perform a predictive role by identifying a potential problem, that is, the presence of particle contamination or moisture in oil, before it has the chance to become a major problem, requiring either complete oil changes or, at worse, repairing damaged equipment. Identified early enough, contamination can be removed by filtration. This assumes, of course, that the equipment’s filter units are themselves efficiently maintained. All too often, filter elements fall foul of the scheduled maintenance approach; changed at fixed time intervals, with little consideration being given to the likely fall off in their efficiency with prolonged use. A partially blocked filter may still remove some contamination, but it will be at the expense of reduced oil circulation, increased pumping costs and a continuing build-up of contamination. Once contamination is detected in an oil line by a condition monitoring system, the first thing to look at therefore is the condition of the filter units. After all, replacing a filter element is a far cheaper option then having to replace a machine’s entire oil or hydraulic fluid inventory. IM *Condition Monitoring Product Sales Manager for Parker Hannifin. SEPTEMBER 2008 International Mining 101