Malfunctioning of Other Mechanical Elements

Misalignment may be due to wear of bearings and in extreme cases of failures it may be difficult to determine whether a bearing or a gear failed first. In case of bearing failures, when lubrication was at fault, either oil did not get to the bearing. Or the proper oil was not used. Where  a common  oil is used for bearings and gearing, the  viscosity of the oil is  generally  a compromise  since  the bearings operate best with  a lower  viscosity oil than  is dictated for the gear sets. Therefore, when bearing trouble is encountered, thought might be given to use of a somewhat lower viscosity lubricant.

Malfunctioning of flexible couplings may also contribute to trouble with gear sets. Such couplings are often used to connect reduction gears with a different piece of apparatus. These  couplings may not only  break but  also  become  jammed, so that  they  are no longer flexible; thus the  gear  shaft will  be thrown out of line. Another possible source of trouble might be a break in a gear case or supports which would permit a shaft carrying gears to be misaligned.

Load Carrying Ability of Lubricating oils at 400 Degree F

Federal Test Method 6511 describes a procedure for determining load carrying ability of lubricating oils at 400 degree F with respect to gears. Using  a  modified  Ryder  Erdco  Test  Drive  System operating  at 10,000 rpm, the  lubricant  to a  series  of  400 degree F controlled tests  at increasing  gear tooth  loads. The  teeth  of one of the  gears  are   then  examined  to  determine  the  scuffing  area. The load carrying ability of the lubricant is rated in accordance with the per cent of the tooth working area scuffed.