Meat Packing and Gear Lubrication

Most of the machinery in meat packing plants is subjected to moisture and thus the conditions are such that rusting occurs. For this  reason  gear  cases  should  be  tight  to  prevent  entry of water. Even so, the gear oils used should contain a rust inhibitor. Another  factor  to  consider  is that  the  temperatures  to  which  the  lubricant  is  exposed  will  be  below  normal. Therefore, low cold test oils should be employed. Gear reduction units found in most packing plants may consist of spur or worm gears. A number  of these  will be on  conveyors and in  general  an oil  of 300 to 500  viscosity  SUS  at 100 degree F  and  containing  both  oxidation and rust  inhibitors  should  be  used. For the worm drives a compounded oil of 125 to 150 SUS at 210 degree F is best. When making frankfurters or sausages, grinders and mixers are used. The grinder will probably be driven by a motor coupled to a herringbone gear. The  mixer may  consist  of a hopper  with  paddle  agitators which  are  driven  through a reduction  gear. In either case the 300 to 500 oil noted above may be used on the enclosed gears. A reservation should  be made  that if gear  reducers operate in a cold  room  where  the temperature  is near  or below  zero, it  will be best  to use  a low  pour  point oil  of 150 to 200 viscosity SUS  at 100 degree  F. Occasionally open  gears  will be  found  in packing  plants. If this is true, residual type oil having a viscosity of 500 to 1000 SUS at 210 degree F and containing a rust inhibitor should be used as needed.

Corrosion prevention by gear lubricants

Ellis et al.^22 consider that staining, tarnishing, and rusting are all  indications of corrosion. The thought is that light stain or tarnish represents the early stages of corrosion since, unfortunately these  changes do not proceed very far before pitting starts. Unreactive gear oils, which have not been subjected to excessive high temperature oxidation, have no tendency  to corrode  metals but, under moist or humid conditions or in the presence of  most salts or acids, do not offer proper protection against  rusting of ferrous  metal  surfaces such as gears. However, additives can be included in gear compounds which will provide rust prevention. Where conditions of incipient rusting prevail, the gears and other metal parts even to the inside of the gear case may require protection, particularly when idle. In such cases not only will the presence of a rust inhibitor but also the viscosity of the base oil be factors. Thus, the higher the viscosity of the gear lubricant, the slower this will drain from the metal surfaces and consequently the greater the rust prevention. Rusting may occur in different environments and various theories are offered as to the mechanisms of corrosion, but normally moisture and oxygen are the offenders

Most rust preventives are polar substances, such as long chain fatty acids, fatty amines, metal sulfonates, certain esters, oxidized petroleum fractions, etc. Such materials wet a metal surface preferentially and displace any water which may come in contact with the steel. The coating of polar substance then acts as a barrier against water reaching the metal surface.

As previously mentioned, controlled  corrosion due  to  EP  additives  is generally beneficial in  that  it  corrodes  away high  spots   on the gear  teeth after  which corrosion may decrease. With the proper selection of the chemical agents, these are not activated except under extreme conditions of load and /or temperature. Further, most of the EP additives which are  used  in  gear  lubricants will have little effect  upon  other  metals such  as bronze, copper, etc; at the bulk oil temperatures maintained  in normal  gear operation .