Providing a boost to bearing life

The new FAG SNS plummer block housing from Schaeffler has been completely redesigned, providing many technical advantages to users, including more even load distribution on the bearings, resulting in an extended operating life. Schaeffler has further optimised the design, resulting in a housing that is not only more cost effective to manufacture, but easier to mount and dismount. Manufactured from high quality, spheroidal graphite cast iron as standard, the housing ensures a high level of robustness and operational reliability. Other benefits include improved lubrication and condition monitoring of the bearings, as well as increased application flexibility and a significant reduction in overall cost of ownership.

Also, due to the introduction of new, industry-standard mounting arrangements and dimensions, the housing can be installed as a direct replacement (retrofitted) for a wide variety of conventional plummer block housings.

Housing design

The special design of the FAG SNS plummer block housing distributes the load on the bearings more effectively (uniformly) than previous housings. 

Using its in-house developed bearing design, calculation and simulation software, Bearinx, Schaeffler is able to analyse different housing designs with various combinations of bearings, enabling the optimisation of the complete system (i.e. housing and bearings). By introducing some subtle geometrical changes, including a small arch-shaped cutaway at the bottom centre of the housing, the load on the bottom roller (at the apex, 180°) is now distributed more evenly across two or three rollers. By spreading the load from the shaft across a greater number of rolling elements, the operating life of the bearing is said to be increased by up to 50%.

In Fig 1, the blue curve represents the rolling element load on a bearing installed in a housing with conventional support. The red curve represents the same load but in a bearing installed in the SNS housing with a cutaway. The red curve has a wider load zone and more even load distribution than the blue curve. In addition, the load on the roller at the apex is significantly higher in the blue curve. However, the red curve demonstrates that a cutaway in the feet of the housing creates a wider load zone. The maximum load from the shaft is no longer supported by the roller at the apex, but by its two neighbouring rollers. 

Lifecycle costs cut

Other design changes have resulted in improved bearing lubrication, mounting and condition monitoring – which together contribute to a reduction in the total cost of ownership.

A lubrication bore with a longer groove has been added to the inside of the upper section of the housing. Different bearing types installed in each bearing position can now be supplied with sufficient lubricant at all times. The lower section of the housing still contains grease outlet bores, which allow for the removal of used or superfluous grease when relubrication is carried out.

To enable improved condition monitoring of bearings, connections are now provided on both sides of the housing as standard for Schaeffler’s FAG SmartCheck condition monitoring device. However, if these two connections are not accessible, a centre mark in the upper section of the housing indicates the optimum mounting position for condition monitoring.

Schaeffler can also supply the housing with connections for its FAG GreaseCheck sensor, a system that continuously monitors the condition of the grease whilst the bearings are operating, and for its Concept 8 automatic lubrication system.

To make mounting even easier, centre marks that indicate the bearing centre line and shaft are provided in the lower section of the housing, which enables fast alignment of the housing. The lower section of the housing also incorporates high precision, machined locating surfaces. These are raised and so allow the use of ledges to achieve precise alignment. Once it has been aligned, the housing can be quickly replaced if required.