Advanced-design bearings from SKF can improve reliabilityFor any operation that relies on industrial vehicles, maximizing the reliability of those vehicles and keeping them operating as productively as possible – is vital to long-term success. In a lumber yard, for instance, forklift trucks and other vehicles must be ready at all times to fulfill the orders of a commercial contractor or a homeowner tackling a major renovation. In a warehouse, those same vehicles must be prepared to keep products or materials moving through the handling process quickly and efficiently. No matter what the specific material handling application, a reliable forklift truck lies at the heart of high productivity and an efficient process.

   While many factors influence a forklift truck’s reliability, one of the most critical is the quality and dependability of its bearings. Bearings can be found virtually throughout a typical forklift truck making their way into components such as the wheels, gearbox, mast and electric motor (in electric-powered vehicles).

   Bearings are important components that can affect the speed of an organization’s processes, its efficiency and even its profitability, says Dave Martin, application engineer for SKF USA. SKF is the worldwide leader in bearing technology and innovation, offering a complete line of bearing products and related services through staff professionals in 130 countries.

   Most operations that rely on forklift trucks are likely to have multiple vehicles. But, as Martin points out, today’s highly competitive marketplace and a strong emphasis on productivity typically force companies to place all of their available vehicles into full-time service. As a result, even a brief episode of downtime can turn into a considerable financial and operational burden -one that can severely impact an organization’s long-term profitability and even its ability to compete.

Reduced assembly solution
For companies that manufacture forklift trucks, the ability to minimize the number of components used is essential for several reasons. First, an increase in components automatically translates to additional steps in the manufacturing process which ultimately slows production and increases costs. Second, the need to use more components in the manufacturing process almost always results in a more mechanically complicated vehicle, which is particularly undesirable for most end user companies.

   “For organizations that use electric-powered vehicles, a heavier-weight truck poses many difficulties,”Martin explains. The forklift truck may require more frequent battery charges, as well as increased maintenance costs and downtime. Both scenarios will ultimately reduce the vehicle’s productivity.

   To enable forklift truck manufacturers to minimize the number of components required during assembly, SKF provides a unique, fully-integrated Hub Unit. This comprehensive wheel-end solution is designed to reduce assembly time and maintenance costs, and reduce the overall weight of the vehicle.

   The Hub Unit is essentially a bearing and seal that is integrated into a housing to create a complete wheel assembly. As a single component, it can be mounted quickly to the axle, requiring no adjustments. This approach does more than just save time; it also reduces the chance of improper mounting or assembly errors that can necessitate expensive maintenance or repair activities down the road.

   SKF Hub Units also minimize costs through their sealed design. Like the Mast Guide and Chain Guide bearings, SKF Hub Units are lubricated and permanently sealed during the manufacturing process. As a result, they require no additional lubrication during their operating lives. SKF offers two types of Hub Units: a double row-style ball bearing appropriate for lighter-weight trucks with capacities up to 2 ½ tons, and a roller bearing design that is ideal for heavy-duty applications.
‘Intelligent’ sensor bearings

   Bearings have also played an important role in the continual evolution of forklift truck technology, enabling manufacturers to improve vehicle performance while keeping manufacturing costs in line. One development that has made this continued innovation possible is the sensor bearing a unique bearing assembly that was first developed by SKF.

   The introduction of sensor bearings to the marketplace grew out of SKF’s response to a particular need within the automotive industry. With the advent of the anti-lock braking system (ABS), the auto industry sought a wheel hub bearing that was ntelligent enough to sense changes in rotational speed. Such a bearing would allow the ABS to identify a potential hazardous operating condition in time to avoid a car accident.

   SKF engineers used this same technology to develop the industry’s first sensor bearings intelligent components that can detect angular variations of the inner and outer rings of the bearing, by generating digital pulses at regular intervals. These pulses provide information about the bearing’s angular position, the direction of rotation, and the speed or acceleration of the rotating shaft. The size of the sensor will dictate the number of pulses generated per bearing revolution which, in turn, impacts the degree of accuracy to which the sensor can pinpoint direction and speed.

   “By providing vital operational information without human intervention, the sensor can provide the signal needed to monitor and control the performance of associated components, Martin explains.

   One forklift truck application in which sensor bearings prove vital is the steering system. Over time, electronic steering systems will begin to replace their mechanical and hydraulic counterparts for a variety of reasons including the opportunity to reduce the vehicle’s weight and keep manufacturing costs in check. This type of electronic steering system – often referred to as steer by wire relies heavily on the capabilities of sensor bearings.

   “When the forklift truck operator turns the steering wheel, the sensor bearing ‘senses’ how far the driver has turned the steering wheel and in which direction,” Martin says. The bearing sends a series of signals to a control unit, which in turns tells the truck wheels how far to turn and in which direction.”

   Sensor bearings also can facilitate automatic positioning of the forklift truck mast an especially helpful function for operations that run around the clock, relying on different operators for different shifts. A sensor bearing can be mounted on the mast, so that it can monitor the mast’s location as it travels up or down. To ensure that the mast “stops” at the correct heights for different shelves or other storage devices, many organizations will pre-program the sensor to recognize those specific heights automatically.

   “This approach takes much of the guesswork out of the process of adjusting the mast, Martin says. It ensures that the forklift truck reaches its desired height as efficiently as possible, no matter who is operating the vehicle.”

   One of the most vital roles of a bearing in any forklift truck application is to facilitate the smooth and continued operation of the truck’s various moving components. Perhaps the most visible application that requires such ease of movement is the forklift truck mast. Here, bearing technology plays a part in enabling the mast and forks to be moved as needed, without difficulty or delay.

Smoother operation
SKF manufactures two types of bearings that can smooth operation of those moving parts. A line of Mast Guide Bearings performs the function of facilitating the mast’s ability to telescope up or down. A line of Chain Guide Bearings enables the forks to be easily raised or lowered to the desired height. In both applications, the ability to accommodate varying loads is essential, according to Martin.

   “The type and weight of the load may vary by application, but in most instances a forklift truck must be able to accommodate both heavy loads and shock loads,” Martin says. Products like the SKF Mast Guide Bearings and Chain Guide Bearings are designed to handle both types of loads effectively.

   The design features of the Mast Guide and Chain Guide bearings reflect their purpose and the environments in which they operate. For instance, both have outer rings specifically designed to absorb impact, which can result from a collision or other unexpected event. The thick outer ring of both bearing styles also enables rotation, which is crucial to these applications.

   Both Mast Guide and Chain Guide bearings offer two options for the inside ball configuration providing the flexibility to select a configuration best suited to the load demands of a given vehicle. Light-duty forklift trucks will typically require only a single row of rolling balls, while trucks placed into heavier duty service will require a double row, angular contact ball bearing design. Both designs are available in a variety of bore diameter sizes, from 30m to 60m.

   Another valuable feature is the fact that both Mast Guide and Chain Guide bearings are delivered fully sealed. Given the conditions under which these bearings operate, Martin says the sealed bearing design is almost mandatory.

   “SKF’s industry research shows that lubrication-related problems cause more than half of all premature bearing failures, he says. Bearings can be under- or over-lubricated, or the wrong type of grease can be selected, or the lubricant can become contaminated over time. Any of those scenarios can cause a bearing to break down long before the end of its useful life.

   To minimize lubrication-related problems, SKF delivers its Mast Guide and Chain Guide bearings as sealed bearings -which means they are lubricated once at the time of manufacture, then sealed for life. This approach ensures that the bearing receives the proper type and amount of lubricant at all times, while helping to ward off contaminants.

   When you eliminate the need to routinely lubricate a bearing, the guesswork often used in lubrication, and the risk of lubricant contamination, you greatly reduce the associated maintenance costs, Martin points out.

Keeping it all together
While the design and production of bearings certainly play a vital role in the end product’s quality and reliability, SKF recognizes that the key to prolonged bearing life lies in a fully integrated approach that takes all critical factors into consideration. This approach is formalized in an SKF program called TFO: Trouble-Free OperationT Program.

   TFO focuses on the four key factors that influence a bearing’s service life: product quality, installation, maintenance and environment. Through TFO, SKF goes far beyond simply providing bearing products to offer a full line of accessories and services that help increase machine uptime and reduce operating costs. Among the many accessories available, SKF offers a comprehensive line of bearing seals, lubricants and lubricating tools that help customers to overcome the challenges of some of the harshest operating environments.

   Another key component of the TFO program is the concept of preventive maintenance affording companies the opportunity to minimize the chance of a costly and disruptive bearing failure. As a critical first step in the preventive maintenance line of defense, SKF provides condition monitoring equipment and services that help companies keep tabs on bearing operating condition. Through vibration monitoring hardware and software, lubricant analysis laboratory services, and a comprehensive roster of training programs, SKF provides the tools needed to spot and avert impending bearing problems before they strike.

   The combination of innovative products and the proactive approach of SKF’s TFO program provides a powerful solution for the industrial vehicle industry,” Martin sums up. Together, these products and services can help forklift truck manufacturers and end user companies to ensure the reliability of their vehicles maximizing their productivity and ultimately boosting the bottom line.”