Construction Equipment in General and Gear Lubrication

While one should  not go contrary  to the  recommendations of the  supplier of construction equipment, practically all enclosed gears  on such  machinery  can  no  doubt  be  serviced with SAE 80  or SAE 90  EP or  MP gear oil. An  exception  are  worm  drives which should be  lubricated with a  compounded  oil  of SAE  140  grade. The use of certain mild EP oils is permissible for the lubrication of worm drives provided the oil supplier so advises. Air and oil filters require the same attention as in the case of tractors. Also drain periods on any construction equipment should be established at a maximum of 1000 hours. It is best to drain immediately after operating and while the gear boxes are warm. If the discarded lubricant is very dirty, flushing of the gear compartments before adding fresh oil is desirable. Open gears will be found on many pieces of construction equipment. For example, large shovels, cranes, drag lines, concrete mixers, etc. The  recommended lubricant for  such  gears is a residual  type  having  a  viscosity of 1000 SUS  at  210 degree F for cold  weather  and 2000 for  warm  weather. If the machinery  is to be used  under wet  conditions, the lubricant should  contain additive which  will  insure that  the oil  adhere to gear  surfaces  when  water is present. Better  still  these  open  gear lubricants  should contain both  EP  and  rust  inhibiting additives. Exposed gears are lubricated as required, often on each eight hour shift. If  railroad  equipment  is used  in  construction, the  tractor  motor gears  can be lubricated  with  the heavier  grade of open  gear oil. 

Wear Prevention Agents

A number of investigators have distinguished between wear prevention and EP agents in lubricants. The  former are  effective  by  a  chemical  polishing action, which  takes  place  at a  lower  temperature  than  does  the  formation of antiweld  films by EP agents. A very  extensive  investigation  of  wear  prevention  agents,  which are  effective  in  lubricants for  two  steel  surfaces was  reported by  Beeck, et  al^9. Calhoun and  Murphy^18, who  reported  on both  anti wear  and EP  additives  for  lubricants found that it  was  possible to  blend  two  or  more  types  of  additives  and  attain both  properties in  the same  composition.

Typical  of  anti wear  additives  are  tricresyl  phosphate  and  Zinc  dialkyl  dithiophosphate.  Such  agents  are  seldom  used  in  industrial  gear  oils  but  are  valuable  in  lubricants  such  as  those  for  jet  turbines  where  the  oil  serves  several  mechanisms  including  gearing.

Lubrication of Special steels

If special alloys are used in one or both members of a gear set, special consideration may be necessary in choosing a lubricant.  The supplier of the equipment will no doubt have the answer since, as Forbes et al. ^20 states:

“The choice  of  metals  that will operate together in a particular type of  reduction  gear is based on practical  data  that have been secured by trial  and error methods  over a period of years.”

It is known that some steels are more difficult to lubricate than others. Stainless steel is very important in this time. Some alloys will not react readily with certain EP elements. Chromium  is  practically  inert  to  sulfur  compounds  but will react  with most chlorine  compounds. Therefore, with high nickel-chrome-molybdenum alloy steels it is important that an EP lubricant contain chlorine additives as well as sulfur compounds.