Tonatiúh Jiménez
SEL Manager Bulk Material Handling
Bosch Rexroth

Advantages of Hydraulic Power in Motor Applications

Mon, 10/21/2013 - 17:35

Crushers, grinders, screens, conveyor belts, belt feeders and apron feeders all need motors and drives to perform their task and ensure the proper and timely processing and transportation of minerals. The drivers and motors used in these machines must combine low speed and high torque. Up until a few years ago, the motors used for mineral transportation and processing equipment presented a series of problems. For example, when a mine purchases a crusher with a capacity of 300 t/hr and uses a traditional mechanically-powered motor of 30hp, the motor’s capacity doubles that of the crusher. This difference forces the crusher and also makes the motor highly prone to jamming. In cases like this, the use of reducers or frequency inverters is counter-productive, since these components reduce both speed and torque. The most common solution is to increase the size of the motor to 60hp. This increase reduces the revolutions per minute (rpm) and delivers the torque of a 30hp motor with a lower speed. But when there is a problem – such as bulk material jamming – the motor must be used to its full power of 60hp, which leads to frequent breakdowns.

Tonatiuh Jiménez, SEL Manager Bulk Material Handling at Rexroth Mexico, mentions that the solution to torque and power specification needs in the mining industry is not the acquisition of oversized motors. “What is needed in the mining industry is normal-sized motors with adjustable speed that can be regulated hydraulically, through a pump instead of a mechanical frequency controller.” In 2011, Bosch Rexroth fully acquired Swedish drive manufacturer Hägglunds, the only company that offers adjustable power solutions to the mining industry through hydraulic motors. As a result of this acquisition, Bosch Rexroth has now expanded its product portfolio and is capable of offering integrated solutions to the mining sector.

Bosch Rexroth’s hydraulic motors provide a level of flexibility unseen in powered mechanical equipment. “If the client, for some reason, requires 100hp instead of 30hp, we can attach another powering unit to our modular hydraulic equipment. This scalable quality allows us to add the number of units that are needed in each application,” Jiménez explains. The physics and operational principles behind hydraulic powering solutions pose great advantages to mining companies using hydraulic motors. Firstly, even if the drive is in a standby mode, it maintains its torque. Secondly, if a problem or risk factor presents itself during operation – such as a jam in a crusher – the motor’s speed can be modified without any secondary effects. “With a hydraulic motor, it is possible to combine a speed of 0 and a maximum level of torque power. The electric motor can work at 1,800rpm,” Jiménez details. Thirdly, the risk of permanent failure in a hydraulic motor amounts to zero. Even in case of breakdowns, hydraulic motors can still function, albeit with hampered efficiency.

Bosch Rexroth provides motors of all sizes and capacities to the mining industry. The company has already installed a 1,600hp motor in a Zacatecan mine and it provides over 8,000KW for another Mexican mining client. In addition, Bosch Rexroth’s modular hydraulic motors and drives reduce energy consumption in mines. “This is something that our clients greatly appreciate,” Jiménez notes. “For example, if you have three hydraulic machines and you need 3,000KW to power a conveyor, it is possible to combine three hydraulic motors and 10 modular units with 300KW in order to obtain the required energy. If at a later stage you only need 900KW, you can stop seven units and thus save 2,100KW. This is our concept of energy efficiency: you pay for what you use and not for what you have.” If one considers the years’ worth of operation in a mine, the resulting energy savings can amount to millions of dollars. Another way in which Bosch Rexroth can help miners reduce energy costs is through the installation of efficiently powered conveyors to recover material from pits and tunnels. The company has built one such conveyor at a mine in Zacatecas. This belt is 1,600m long, and it eliminated the need to purchase 70 heavy load trucks at a mine site in Zacatecas.

Furthermore, Bosch Rexroth abides by an integrated service philosophy. The company considers the mining industry one of its priorities. Its strive for quality begins in Mellansel, Sweden, where all of Bosch Rexroth’s motors are manufactured. Afterwards, Bosch Rexroth visits mines and demonstrates the performance of the equipment in the field. The company assists clients in the selection process of the best-fitting equipment for each need, installs the product, puts it in operation, and handles all the replacements part and maintenance required. “We do not have distributors. We directly manage the sale of our products and the integrated services we provide, such as long-term maintenance in mines through PMAs,” Jiménez states. Bosch Rexroth also possesses specialized monitoring equipment and technology that allows the company to receive detailed information on product performance and therefore prevent wear in the machinery. The company can determine equipment lifespan and prevent any breakdowns.

By introducing hydraulic motors to innovative mining applications, Bosch Rexroth has enabled mining companies to adapt their power supply to their needs in a particular process and production stage. “With our hydraulic motors, our clients will always be able to meet their production goals by programming and adjusting their motors and drives,”says Jiménez. “Bosch is a global group that comprises 50 companies, and its solutions have been developed for more than 50 years,” he states. Bosch Rexroth Mexico, part of Bosch’s industrial division, is focusing on furthering the quality and efficiency of its solutions towards the mining industry. The company has adapted its business strategy to the industry’s needs and will continue to foster innovation in the sector and support mining operations throughout Mexico with integrated solutions and services.