Flour Milling and Gear Lubrication

Up to time grain enters the mills, conveyors are used for handling. These  may  take the  form  of screw,  bucket, ribbon or belt and  any  one of these  types can be  driven  by gear  reducers. A  turbine type of oil  having  a viscosity of 500 SUS  at 100 degree F,  that  is AGMA  No. 3 grade, can  be  used  throughout  these  gear  reducers. In  the  northern  states  this  oil  should  have  a pour point  of zero or lower. An  oil of this  viscosity  will not cause excessive  power   loss and  yet  it  will  protect the  moving  gear  teeth.

Gear motors may be used for some conveyors and blowers. The  same  type  and viscosity of oil  should  be  satisfactory  for the  bath  lubrication  of such  gears, especially  if bearings are  serviced from the same  source. Where the drives in gear motors run quite warm, an oil of about 750 viscosity SUS at 100 degree F or an AGMA No. 4, may be desired. If such motors have a plate showing the recommended viscosity of oil, this suggestion should be abided by.

A tight  housing  is  essential  in any  of the gear cases in flour mills, more  from  the  standpoint  of prevention of contamination  from dust  than  from  leakage. Since  the oil  level  in gear  cases  should  be  inspected  every  month  or  sixty days, care  should  be  exercised that  dust  does  not enter  when  the  filling  plug or cap is removed.

Open  gears  are not  used too  often  around  flour mills; but if  these  are  encountered, it  is wiser to use  a  light  oil  as the  lubricant  rather  than  a  residual type. This can be the same oil as suggested for use in conveyor gear reducers, that 500 viscosity SUS at 100 degree F. As  such an oil  becomes  mixed  with dust, the paste formed will  slump off rather  than pack  in  the  bottom  of gears; thus, misalignment should  not be a  problem.  

Flour mills  may  be  self contained, in that cleaning, tempering, grinding and  sifting may  all take  place  in one  enclosure, or the latter operation  may be  separated. Such machinery will vary, but often the rolls are driven by gears. Here again the turbine oil type 500 viscosity SUS at 100 degree F can be used. Machinery handling middlings or bran will be much the same as previously mentioned and if gearing is used, the same recommendation will hold.  

In the manufacture of corn meal or animal feeds the same type of processing and machinery will be found. Thus, conveyors  and screens  will have  similar  drives but the  crushing or milling  can be  by  rolls  or  discs. In any event the gear oil used can be the same type and grade as recommended for flour mills.

It will  be noted that  a simplified  lubrication  application for  reduction  gears  is suggested  in grain mills, that is, a  single  oil  throughout with one  exception. This  is in  gear motors and even here  the  sanction  of the motor manufacturer  might  be  obtained for use  of the  500 viscosity  oil.

Lubrication of Gear Sets on Agricultural Equipment

While some open gears are still encountered on farm machinery, modern equipment, for the most part, has precision cut gear sets operating in enclosed gear cases. Therefore, most gearing on farm machinery can be satisfactorily lubricated with two types of gear oils.

First , for  open gears  a  residual  type  of  adhesive  gear lubricant, which can  also  be used on  wire ropes  and  some  chains, is  recommended. Such  a  lubricant is available as a material  which will  hardly  pour at ordinary temperatures  and  must  sometimes be  heated in  order to apply. Much more convenient is a cut back from of such lubricants which can be applied by pouring or dipping. Likewise, aerosol containers of the same type of material permit spray application.

The enclosed gearing on farm equipment is bath lubricated so that the partially submerged gears, when in operation, pick up the gear oil and where necessary, transfer a portion to bearings. While  it is  not  possible  to  list every  variation  in the  mechanisms of  gearing  on  agricultural  machinery, the  rules for  lubrication of such expensive  and  often  intricate  equipment follow  general  pattern. That is, the use of the proper gear lubricant in the proper amount and the regular replacement of such oils as required.

While the  recommendations  of  the  manufacturer  are a  guide  as to the proper  gear  oil to use  in each  piece of  equipment, there  is a  tendency  to  simplify the  number of  lubricants  required  on a farm. With this in mind, multipurpose gear oil will serve most enclosed gear sets. This  can be  a  mild  or  regular EP  type with  the  use of an SAE  140  grade for   hot weather  and  an SAE 90 grade  for  winter. In very cold weather an SAE 75 grade of gear oil can be used.  The  matter  of  reduction in the number  of  lubricants  necessary  for  farm  equipment  will have  further mention in  the next section. It  will  then be  evident that  manufacturers   of  such  machinery also  have  this  in  mind.     

Limitations on Heating of Lubricants for Application

Heavy bodied lubricants, particularly residual types used on exposed gears, are often heated in order to make application easier. If such lubricants are straight mineral oil products, the amount and intensity of heat should not harm them. However, if additives are included, only a very moderate heat should be used. Otherwise some change in the composition is possible. A supplier of the lubricant can advice the limitations on heating. A similar caution is necessary in case lubricating greases are used as gear lubricants. The thickeners for such products may be soaps which upon the application of considerable or prolonged heat will separate from the oil present. 

Nonferrous Metal Rolling Gear Lubrication

Metals such  as aluminum, brass, copper etc., are  rolled  into  sheets or  other  shapes in  continuous rolling  mills designed  somewhat like those  found in steel  mills. Modern mills use circulating oils to lubricate the gear drives, pinion stands, and journal bearings. Either mild EP or MP gear oils of a noncorrosive nature can   be employed in such service. The  grade  of  oil  will depend  upon the speeds  of the gears  and  may  vary  from an  SAE  80  to an SAE  140. In  screw down  equipment  either of the above  type  of oils  or a straight  mineral  oil  can  be  used. Where  any  of the above  drives  are  through open gears, a residual  type  of gear  oil  containing  a  rust  inhibitor  and having  a viscosity  of 1000 to  2000 SUS at 210  degree F  should  prove  satisfactory. The  best  practice  is to  apply  such a lubricant automatically so as  to  insure a coating on  the  gears  at all  times. 

Carbonated Beverages and Gears

In preparing   beverages, gears are often used on meters to synchronize delivery of syrup and water to carbo coolers. Also on automatic   bottle cleaners, gears are used to rotate brushes both on the inside and outside of the bottle. These latter gears are often flooded with the detergent   solution used in washing and other lubrication is not permitted.

Conveyors, in such  establishments, when  driven  by  reduction gears,  can be  serviced  by  an  oil  of about  500  viscosity SUS at 100 degree F, if enclosed, or a residual  type  of about  2000 SUS at 210 degree F, if of the open  type.

Hand application of Gear Lubricants

Hand  application of gear lubricants, while often used on slow speed  exposed gearing, should  be discouraged because  there is  always  a certain  amount of hazard to  such a procedure, the amount  of lubricant used is indeterminate, and  the operation is wasteful of both time and lubricant. However, primarily because of the lower initial cost, open gears have considerable use. Also, both location of the gears and immediate economy, dictate hand application of lubricants to such gears. Consequently, some of the methods of hand application follow:

(1)    By paddle, when the lubricant is a heavy residual type or consists of a solid or stiff grease. Usually more of the lubricant than is necessary is applied and consequently the excess either   drops off or is thrown off into the surrounding area. This is not only wasteful but also contributes to poor housekeeping.

(2)    By hand in case the residual type is heavy enough. Such a product can be formed into a ball by hand and then dropped into the gear mesh where in time it is distributed.

(3)    By bags, made of plastic, most often polyethylene, which is filled with the gear lubricant. A filled bag is dropped between the gear teeth where eventually it is chewed to pieces by the gears and the lubricant is released. This makes a somewhat cleaner operation than the previous methods and the hands are not soiled while applying the lubricant. If a large opening is provided in a gear case, this method of application can sometimes be used for enclosed gears.

(4)    By pouring from a can, bucket, or any spouted container. Such applications are made at intervals and in case of gear oil is very heavy, it may require heating to reduce the consistency before applying. The lubricant is then poured in a fine stream into the teeth as the gears slowly revolve toward each  other. If the oil is applied relatively frequently in small amounts rather than at longer intervals in large amounts, there will be less chance of its being thrown off.

(5)    By hand spray at intervals, most often from “ AerosoI” containers. Such a package, which ordinarily holds up to a pound of a diluted gear compound, makes for ease of application and cleanliness because an excess of the lubricant is not applied. The gear compound is diluted with a non-inflammable solvent which evaporates rapidly after release from the container and leaves a viscous coating on the gear teeth. While the diluents present may be toxic, the amount released at one application is normally so small that it dissipates without harmful effects.