New mines, customers and technologies require speedy support, broader distribution networks and higher education
As conveyors get longer, process equipment gets larger and duty cycles are stretched to meet production demands, the driving force behind many of these items—typically, workhorse mechanical gearboxes and speed reducers—will be expected to handle bigger loads and higher temperatures along with all of the other physical stresses experienced by rotating equipment. This means that not only will industry vendors need to ensure their sales and parts-supply networks can meet rising demand for purchase, repair and replacement services, but also that their customers are kept aware of new mechanical-drive technologies and the maintenance needed to keep the machines running. As discussed later in this article, even a factor as seemingly straightforward as gearbox lubricant selection may involve a series of decisions that could affect machine efficiency and service life.
Apart from the general information typically presented in a company’s sales literature and Web site pages, a number of leading gear-unit suppliers offer various levels of both online and classroom-type training in product familiarity, application selection and advanced technical instruction. Emerson Industrial Automation’s Power Transmission Solutions business unit, for one, is active in this sector, offering a range of training courses for customer personnel that includes interactive online training, as well as 3- to 4-day regional distributor schools and master schools for advanced training. For more general information, the company recently released a new product app for the iPhone or iPad that allows users to browse digital versions of Power Transmission Solutions’ catalogs and interact with the content.
Meanwhile, several of the industry’s major gear-unit suppliers recently announced the establishment of new facilities to support customers in what may have been regarded as under-served and/or rapidly growing regional markets.
In late April, for example, Hansen Industrial Transmissions NV (HIT), which was acquired by Sumitomo Heavy Industries (SHI) in March 2011, announced that its European assembly center in Antwerp will integrate engineering, production, assembly, sales and service of SHI’s Paramax industrial gearboxes for the Europe, Middle East and Africa (EMEA) regions.
The announcement is another milestone in the global integration of Hansen into SHI—a process that is still ongoing in most parts of the world, but has now been finalized to serve the EMEA market, according to the company, which noted the new facilities will provide a clearer product strategy for the EMEA region, offering customers a more useful selection of choices to serve both high- and low-torque applications from HIT’s P4 and SHI’s Paramax gear unit lines, with capacities ranging from 3 to 1,100 kNm, all available from a single source.
Sumitomo noted its Paramax 9000 series parallel and right angle drives are built on almost seven decades of experience in power transmission engineering. The Paramax 9000 series parallel and right angle drives are available in 26 standard housing sizes, with torque ratings up to 4.9 million in.-lb. The line’s universal housings accommodate horizontal, vertical and upright installations, and a modular design concept allows direct motor mount for right-angle units. According to the company, a new fan and shroud design delivers up to 87% increased thermal capacity, cooler operation and greater efficiency.
In addition, the Paramax 9000 Series BOSS conveyor drives are specifically designed to meet the needs of the materials handling industry, with key features that include 10 housing sizes, with universal design that accommodates flippable horizontal applications for greater mounting versatility. The BOSS conveyor drives have a cast iron housing designed to minimize deflection under load, while oil bath lubrication allows for a full range of operating speeds without the need for pressurized lubrication systems.
All BOSS conveyor drive sizes feature split gear cases, and anti-dust air breathers and taconite seals are available items. Other options include internal backstop, hollow shaft—with shrink disc or keyed, oil drain valve and oil level gauge, immersion oil heater, split fan shroud, oil coolers, ductile iron or fabricated steel housings and an auxiliary inching drive designed to handle full-load capacity.
Expanding in Australasia
Recently, another major mining industry supplier, SEW-Eurodrive, reported that it expects to slash gear-unit turnaround times with the launch of its Australian-assembled Mining Drive, following the acquisition of a new Industrial Gears (IG) facility in Melbourne, Australia.
The Mining Drive features bevel-helical technologies and is suitable for motor power up to 1,500 kW. Assembled with a purpose-designed thermal housing, SEW-Eurodrive claims the Mining Drive is set to make a significant reduction to energy usage in heavy industry through the lessening of thermal losses. The local-assembled Mining Drive line will include eight sizes, up to a torque limit of 175,000 Nm.
SEW-Eurodrive National Industrial Gears Product Manager, Ian Tribe, said the Australian-assembled Mining Drive—now available in that regional market—features a modular design and is assembled from a range of standard components. “The modularity of the Mining Drive allows for shortened delivery times, as units are assembled from stock parts. Unlike gear units manufactured overseas, the Australian-assembled Mining Drive can be supplied in just a few weeks, allowing users to streamline their project timelines.”
Along with the purpose-designed, cast-iron housing, the Mining Drive incorporates several internal energy-reducing features selected specifically for each application, depending on the operating conditions. “These features result in less heat to be dissipated by the housing, and housing is designed with larger dimensions and extensive ribbing on both sides and underneath in order to dissipate the heat that is generated more effectively,” Tribe said.
U.K.-based gear-unit builder David Brown recently announced the official opening of a new industrial gearbox service center in Indonesia, offering strip, assembly and test facilities. The company said the new facility, located in East Java, has the capability to service, repair, upgrade and provide strategic maintenance for its mining customers as well as others in various industrial sectors.
The opening of the Indonesian facility is part of the company’s stated global strategy to provide industrial gearbox service and support to its customers throughout the world. Since early 2011, David Brown has opened new service centers in Southeast Asia, the Middle East and in South America, and has plans to open additional service facilities in strategic locations in North America, South America and India, as well as another facility in Africa. It also recently acquired UniGear, a major North American industrial gear manufacturer.
New Service Capability Matches New Drive Technology
As reported last year in the April issue of E&MJ, Rexnord opened a 29,000-ft2 gearbox repair and remanufacturing facility in Salt Lake City, Utah, USA, to serve mines and other customers in the western U.S.
According to Rexnord, the Salt Lake City operation has the capability to handle up to 50,000-lb (22,680-kg) gearboxes, can provide complete gearbox rebuilds as well as reverse engineering and custom unit service and can repair or rebuild gearboxes of all makes and brands. Other Rexnord gearbox repair and replacement facilities in the U.S. are located in Milwaukee, Wisconsin, and New Orleans, Louisiana.
Rexnord introduced its newest gearbox product line, the Falk V-Class, in 2011, offering a number of advanced design innovations that include a horizontally split housing, with its shape and features designed through the use of Computational Fluid Dynamics (CFD) to enhance the drive’s thermal dissipation qualities. Cooling fins on the housing help to reduce oil temperature, and proprietary oil feed passages in the housing improve lubrication and provide additional cooling capability. An oil sampling port is built into the housing to allow quick checking of oil condition. The V-Class drives also have no-leak seals with oil drainbacks and a purgeable grease chamber.
New design elements improve the line’s torque capacity, including 25° pressure-angle gear teeth; case-hardened, ground gears; optimized bevel and helical tooth forms that ensure full contact under load; proprietary peened gear teeth; gear sets up to AGMA Class 12; and a heavy-duty ductile iron housing that withstands shock loads. Features that improve installation, serviceability and replacement characteristics include removable, adjustable feet that allow drop-in replacement for current product lines, and can adapt for replacement of competitor drives and different shaft centerline heights. Base-mounted units can be repaired in place, and the split housing allows easy disassembly/assembly for maintenance of bearings and gearing.
More recently, Rexnord unveiled an inching drive option for the Falk V-Class gear drive, as an optional package that will enable that product line to offer reliable, full-load inching operation to allow slow-speed operation of equipment for inspection and maintenance purposes. It can also be run continuously to prevent freeze-up of components in harsh environments and cold weather during idle periods.
The inching drive utilizes a Falk Ultramite gear drive that is integrally mounted to the main gear drive unit, coupled via an overrunning clutch. This allows the inching drive to be automatically disengaged when the main motor is operating.
Looking at Lubrication
An emphasis on thermal protection—and even more attention to lubrication reliability, efficiency and flexibility—is apparent in just about every product announcement issued by the major gearbox suppliers. Failure to maintain constant and proper lubrication of heavily loaded components can result in performance degradation ranging from reduced overall efficiency to catastrophic failure.
What kinds of internal activity are gearbox lubricants subjected to, and why is it so important to use the right type of lubricant? Todd R. Bobak, chief research and development engineer at Sumitomo Machinery Corp. of America, described the principal issues in a recent white paper.1
For internal gearing, the use of the appropriate lubricant is crucial to obtaining maximum service life and reliability of the gearbox, according to Bobak. The function of the lubricant is two-fold: first, it provides a thin film between the internal rotating components as well as the gear teeth in mesh, thereby preventing direct metal-to-metal contact; and second, it provides a medium in which heat—developed through normal unit operation—is dissipated.
The type of lubrication used in a gearbox plays a role in the overall efficiency of the unit, he noted. As the internal gearing moves through the lubricant, the lubricant is continuously displaced by the action of the gears striking it. This is typically known as churning loss since power that could otherwise be used for the application is absorbed (or required) by this action of the gearing striking, pumping or moving the lubricant. For example, a gearbox lubricated with grease would be less efficient than if it were to be lubricated with oil. Intuitively, this makes sense because grease is typically thicker than oil and it requires a greater amount of power to move the gearing through it.
Another avenue for loss in efficiency specifically related to gearing and lubricant is what is known as windage loss. As the gearing rotates through the lubricant, and then out of the sump, a certain amount of lubricant adheres to the surface of the gear itself. Since the gear is rotating, centrifugal forces cast the lubricant adhering to the gearing into the enclosed atmosphere of the speed reducer casing. This action may serve to create a lubrication “mist” through which the gearing must pass. In essence, this mist is another barrier for the gear to pass through thereby requiring (or diverting) power which otherwise could have been utilized as usable output torque.
To quantify the effects of lubricants on speed reducer efficiency, testing has been conducted by Sumitomo on a planetary gearbox of a given size and reduction ratio (4:1). This efficiency testing was conducted twice: once with the gearbox lubricated with a grease of NLGI Grade 2 (a moderately soft grease with the approximate consistency of peanut butter) and again with a grease of NLGI Grade 00 (a semi-fluid grease with the consistency of applesauce). Other than the lubricant, no other components within the test units were changed. Post-test results revealed that the speed reducer lubricated with the NLGI 00 grease had an efficiency of 92.1% whereas the same unit lubricated with the NLGI 2 grease was 90.9% efficient.
That is not to say that oil lubrication for a gearbox is distinctly preferred over grease, explained Bobak. Grease has the advantage in that it may provide for universal mounting of the gearbox (i.e., output shaft vertical up or vertical down); its replenishment/replacement interval may be longer than a comparably sized oil lubricated unit; and grease is less likely to leak through the shaft seals of the unit.
Finding the Right Product
As explained in E&MJ’s sister publication Coal Age (See “Matching Lubricants with the Mine’s Needs, p. 52, April 2012), what most miners know is that a machine cannot be adequately lubricated unless the maintenance crew understands the equipment and the environment in which it operates. That’s a position with which Bel-Ray Lubricants identifies; it has been actively involved in mining for 45 years and has studied each piece of equipment and the environment in which it operates before developing a lubricant for the application, explained Don Howard, Bel-Ray’s R&D manager.
Bel-Ray believes lubricants should be developed specifically for mining applications. One of the ways it is showing its level of commitment is through its Total Lube Partnership (TLP) program. “We analyze components and centralize lubricating systems,” Howard said. “We look at performance and consumption rates. The object is to maintain the optimum level of lubricant consumption that provides the right amount of lubrication economically. We look at root failure analysis. The TLP is our effort to become totally involved in the lubrication aspects of our customer’s machinery.”
While unexpected catastrophic failures are rare in the mining business, bearing and gears do eventually wear out. “When a failure does occur, we will send a team of people out to the site,” Howard said. “Most of the time we are looking at gear or bearing failures and we have people who are very familiar with root cause failure analysis of gear systems and the different modes of wear. We can usually get a good idea of how and why a component failed, the mode of failure, and submit a complete report to the mine with our findings and recommend corrective actions.” Bel-Ray will also send independent experts into situations where the customer wants an independent verification.
Over the next several years, Howard believes the industry will use more synthetic products for gear oils and open gear lubricants. Increased use of synthetics will come about as miners begin to understand the benefits of these products. “They will soon realize that you pay more, but they can be used twice or three times as long because they are highly filterable and extremely stable,” Howard said.
Once the mines grasp this concept, they will realize the true benefits of synthetics, he explained.
1 Bobak, Todd R., How Green is Your Gearbox?, White paper, Sumitomo Drive Technologies, http://www.smcyclo.com/modules.php?name=Pages&sp_id=275.