Food processing Industries and Gear lubrication

A variety of industries are grouped together so that prevention of contamination by gear or transmission lubricants can be stressed. While such possibility is remote, Government Inspectors are becoming more particular in this regard. Also, both  manufacturers  of food processing  machinery  and operators of plants are  aware  of the  importance of cleanliness  and lack  of contamination. Proper seals, well maintained, should prevent leakage from gear cases. As an aid in this direction, over lubrication should be avoided and when and if lubricating grease is applied, this should be at very low pressure. As a general rule, straight petroleum oils can be used in gear lubrication of the subjected equipment. Some operators of machinery handling foodstuffs prefer light colored lubricants. White oils are available in viscosities up to 300 or perhaps 500 SUS at 100 degree F. The  same  oils can  be  thickened  to  a  semi fluid or non  flowing  nature  by the  use of fine silica  or non toxic  soaps, such  as  aluminum  or calcium. Light  colored  fillers, such  as  magnesium  oxide  or zinc oxide, can be added to  lubricating greases, although fillers have little  if any  place  in gear  lubrication.

Caution  should  be  used  in supplying  gear  lubricants containing additives  to  food  processing  plants. Oils  containing  EP agents should  only  be  used  if the gear  cases  containing such  oils are  sufficiently  removed  from  the food  products so that  leakage  will  cause no  contamination. Foam inhibitors are permissible because the concentration is quite low. Stable oils are recommended because they will require a minimum of oxidation inhibitors. Such additives, as well as  rust  inhibitors, which  will  be  desirable  under  wet  conditions, should only  be used  with assurance  that  the compounds are not  harmful to  animals  or humans.

Simplification  of gear  lubrication  should  be  kept  in mind and  if  possible, only  one type  and grade  of gear  oil be used in a  specific  plant. Thus, in spite of the  recommendations above for the  use of such oils  with  very  judicious  inclusion  of  additives, the suggestion  has been made^31  that  a  premium  grade  rust  and oxidation  inhibited turbine and  hydraulic  oil  be  used in all  gear reducers  in dairies. Therefore, similar oils will also be recommended for other foodstuff handling equipment. Open gearing will be found in some food handling machinery or plants.  It  is  presumed  that such  gears  will  be so located  that  drips from  the  same  will  not  contaminate food. Therefore, a  general  recommendation  is to  apply  a  residual  type  of  gear  lubricant  very  sparingly. The viscosity will be dictated by the service but will probably be one of 1000 to 2000 SUS at 210 degree F.

In the  group  to  follow, equipment  used  to process some medicinal  items, alcohol  products etc., will be  included since  they  are  restricted   to the  same  limitations as far as contamination is  concerned. By  mentioning  some  of the unit  operations  which may be  encountered   in food  processing, the  variety  of machinery  involved and therefore,  the  possibility of the  use  of  gear  drives will   be  evident. Thus, cleaning,  coating, conveying, decorating,  disintegrating, drying, evaporating, forming, heating, mixing, packaging, pumping and  separating are a few  such  operations. 

Prevention of Contamination of Gear Lubricants

Gear sets operate under such varied conditions that it is difficult to give general suggestions for prevention of contamination of the gear lubricant. The two contaminants most often encountered are water and dust. In the latter are included large particles such as scale in steel mills. Less trouble is encountered where a circulating  system  provides  the  lubricant  rather  than  a  splash system, since the former  can  be  supplied  with settling  tanks  or filters. Even here regular inspection is necessary and accumulated water should be drawn off whenever noted. Such accumulations may  be quite  large  in the case of  gear  oils  for  ship  propellers or in oils servicing  paper  mill  machinery  or steel  mill  gears.

Where  gear cases  are  vented, the location  of the vent or a pipe  connection to the  same  should  be so  located  that  the least  dirt  possible  can enter. One automobile  manufacturer reduced  contamination in  differential cases by  extending  a  line  from  the  vent  and  securing  it  forward  under  the  car  frame  with  the  opening  toward  the  side  of  the  vehicle.

Prevention of contamination of lubricants by chemicals must have individual consideration. In  extreme  cases it  may  be  necessary  to  provide  pressure  on  gear  cases to  prevent  entry  of contaminants.