Brockway Conveyors have done an out-board type roller with taper roller bearings sealed with grease. ■

Seal-for-life greasing of tapered rollers is not condoned by the bearing mfgrs. Some do it when the ambient temperature variation is small such as in underground mines or in tunnels.

Special greases have been tried. It is a continuous trial by the operators to see if they can get away without tapered roller bearing greasing. Molydisulfide (fine sphere) grease additive has been somewhat effective.

Since the tapered roller acts as a grease pump, history has shown greasing is the norm.

I also hope to learn from the question.

Lawrence Nordell

Covneyor Dynamics, Inc. ■

Dear Baskar..

Here in South Africa we used to use the Jeffrey "Permaseal" idler roll which was as you described, with permanent seals and taper roller bearings greased for life.

These were extremely successful, (and I have a 3.5km horizontally curved overland conveyor still running on them after 12 years).

Although it was thought by many that the good life was due to the high load rating of the bearing, many considered it to be attributed to the very good sealing properties of the permaseal that protects the bearing.

After all, an idler is only as good as its seals.

This type of idler is seemingly no longer in normal use here now. Probably not competitive against the conventional ones, as the bearings are expensive and the shafts have to have more conservative diameters to avoid deflection under load at the bearings, for which is less is allowed for taper roller.

Best regards

LSL Consulting & Tekpro Projects ■

A couple of comments:

1. The Jeffrey Permaseal rollers referred to by Graham Spriggs, although not regreasable had a grease reservoir. This had the form of an inner tube running over the shaft between the bearing housings, which was filled with grease.

2. The taper roller bearing has to be accurately set in order to obtain good performance.

3. As per G Spriggs' comments the shaft diameter has to be increased to reduce the effects of bearing misalignment on bearing life. Developments have resulted in improvements, but, based purely on design, it is still prudent not to exceed angular deflections of the order of 4minutes of arc when using taper roller bearings (as compared to 8minutes generally for deep groove ball bearings).

4. The effect of sealing in idler rollers is extremely important. The company I represent, Melco, have rollers (of ball bearing type)running in the Syferfontein overland conveyor system for 13 years with a total failure rate to date of about 12% of the original supply. ■