Metering valves cut lubricant consumption
by 25 per cent on linear guidance systems

By incorporating special lubricant metering discs on its range of linear recirculating roller bearings and guideway assemblies, Schaeffler has reduced lubricant consumption by more than 25 per cent compared to conventional designs.

A range of linear recirculating roller bearings and guidance systems are now available with special lubricant metering valves, which provide precise doses of lubricant to the linear guides, reducing lubricant consumption by more than 25 per cent compared to standard designs, reducing maintenance and servicing costs and preserving resources for the customer.

Schaeffler's RUE-E range of roller monorail guidance systems can now be fitted with special lubricant metering valves to ensure that the lubricant is precisely metered under all operating conditions, regardless of the guide's mounting position. This is made possible because of several key design factors.

First, Schaeffler uses a patented injection moulding technology to produce the saddle plate, which, combined with the various connection options for relubrication at the front, rear and side of the carriage end, and the special design of the end pieces - the lubricant is directed precisely at the rolling elements. This not only minimises relubrication quantities, but also improves the reliability of the guide and is kinder to the environment.

John Loonam, Linear Product Specialist at Schaeffler UK comments: "Basically, the O rings in a standard linear guidance system are replaced with the SMDS metering valves. A paper seal is placed between the end plate and the lubrication duct, which prevents leakage of the lubricant from the ends, resulting in a reduction of more than 25 per cent in lubricant consumption compared to standard designs. Only one valve per side and rolling element loop is required and one lubrication connector per carriage."

Several years ago, Schaeffler's Linear Technology specialists developed a relubrication and sealing component kit that contained a metering system for minimising lubricant quantities and various sealing elements. These provided optimal sealing of the lubricant duct for the standard INA-branded roller monorail guidance systems.

The latest SMDS integrated metering valve option offers high reliability with only one lubrication hole per carriage, independent of the roller monorail guidance system's mounting position and operating conditions.

With conventional roller monorail guidance systems, the relubrication duct between the lubrication hole on the linear guide and the rolling elements can become empty, depending on the mounting position and operating conditions. This means more lubricant is required during relubrication to ensure reliable operation and because it takes the lubricant longer to reach its desired destination. With centralised lubrication systems, only one specific dose is provided per impulse, which can be a problem. This can lead to the lubricant arriving late in the rolling elements or, at worst, lubricant starvation. This problem is exacerbated when the guide is mounted at an angle of 90 degrees, often resulting in insufficient supply of lubricant to the upper rolling element rows. In extreme cases, this can cause damage to the rolling elements and raceway, leading to the complete failure of the linear system.

The new SMDS metering valves replace the standard O-ring seals. These prevent the lubricant duct from running dry, avoid inadequate lubrication or over metering, and allow precise relubrication with very small, precise quantities. The linear guides have only one valve per side and function irrespective of mounting position.

For further information on Schaeffler's RUE-E SMDS range of linear recirculating roller bearing and guideway assemblies, e-mail: info.uk@schaeffler.com  or view website: www.schaeffler.co.uk    Refer to page 79

Split bearings slash maintenance costs on bucket wheel excavators

By replacing a standard spherical roller bearing on the drive shaft of a bucket wheel excavator with a new split spherical roller bearing from the Schaeffler Group, Pilbara Iron is now saving 27,500 euros each time a bearing is replaced.

Repair and overhaul of components on large high capital cost plant and machinery soaks up valuable time and resources, often resulting in costly production downtime, while the machine is offline being repaired. Harsh operating environments can also mean more regular maintenance being required on certain types of machinery.

Split spherical roller bearings are particularly useful when several solid spherical roller bearings are being used to support a complex drive shaft, or where the bearing needs replacing but is located in a tight space on a machine, so access is restricted.

Pilbara Iron, a member of the Rio Tinto Group, operates mining, rail and port facilities. The company operates two shipping terminals in Dampier, Australia. Each terminal is equipped with train unloaders, iron ore storage and blending facilities, and shiploaders.

A bearing on the main drive of a bucket wheel excavator at Dampier had to be replaced recently. The bearing, an FAG standard spherical roller bearing from Schaeffler, was difficult to access and required that the transmission shaft be dismounted first. This meant that replacing the bearing was a lengthy, labour-intensive process. Pilbara Iron estimates that it loses 72 hours of production downtime each time this type of bearing needs replacing.

Following a recommendation from Schaeffler Australia, Pilbara Iron decided to replace the standard spherical roller bearings with FAG split spherical roller bearings. These bearings have a diameter of 620mm and weigh 210kg. Due to their split design, the bearings can be mounted into the existing housing without having to remove the transmission shaft.

When the new bearings were actually fitted to the main drive on the bucket wheel excavator, production losses were cut by 50 per cent, while maintenance labour costs were also significantly reduced.

Although the cost of purchasing a split spherical roller bearing is several times higher than a conventional version, the potential for cost savings over the life of the bearing is enormous.

At Pilbara Iron, the cost benefit amounted to 27,500 euros for each bearing replacement. The company also benefits from long term savings in maintenance costs, since the split spherical roller bearings enable faster and simple bearing replacement.

With split spherical roller bearings, the inner ring, outer ring and cage assembly are split. A cylindrical bore provides direct mounting onto the shaft. These bearings typically offer high thrust load capability and dynamically compensate for any misalignment.

With the FAG range of split spherical roller bearings from Schaeffler UK, the outside diameter, outer ring width and shaft seat diameter are identical to the dimensions of the standard spherical roller bearings range. This means customers can easily replace solid bearings with split versions with an adapter sleeve.

Mounting of split bearings normally leads to a reduction of machinery downtime and maintenance costs, particularly in those industries where the value of capital equipment is normally high, including mining, quarrying and mineral processing. In many cases, split bearings can also reduce the cost of new designs, because the bearings simplify the assembly process and mounting procedure.

As well as bucket wheel excavators, split spherical roller bearings can also be found on winch drums, screw conveyors, mixers and stirrers, mills, crushers, rotary kilns, fans and blowers, drive and line shafts, which all require regular maintenance, repair and overhaul.

For further information on FAG Industrial Services, view website: www.fis-services.com    Refer to page 79