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.

Nuclear Power plants Gear Lubrication

Present indications are that the principal gearing in nuclear power plants will be in connection with turbines. Such  reduction units should be  far  enough removed  from the area of high  radiation that no degradation  of the oil  from such  a source  will occur.

Cox et al.^14 who have considered this matter state: “Irradiation tests of turbine oils show that maximum expected radiation doses in  current and projected power plants over a twenty year period  does not change the  physical  properties of the oil. Oxidation stability and other properties are, therefore, still of most importance in turbine oil selection”.

Also  Okrent^43  in treating  design considerations of nuclear powered  surface vessels concludes that the  reduction gearing  in connection with  the  turbine presents no problems  from a radiation standpoint. In spite of the  above thoughts, Watson^51  mentions  that in  nuclear  power  generating  stations, a  number of applications  will be found where  gears  should  be run  without  lubrication. Experiments were, therefore, made with various materials, run in a dry state, with latter wear. As a  result, it is suggested that if loads are not heavy, spur gears, made of  case hardened  En steel, phosphate prior to coating  the flanks with  molybdenum  disulfide, can  be run  continuously, in a dry state, without  measurable  wear. Also  a worm wheel , made  from  woven  asbestos base  with  a case  hardened  steel worm, is promising for  operation in a dry  state.

No doubt, when and if gear oils with radiation resistance are necessary, suitable fluids will have been developed. Thus, polybenzenoid   compounds containing short alkyd groups show promise in such applications.

One  interested  in this subject might  avail himself  of a series of  eight  papers devoted to “Non-conventional  Lubricants  and Bearing  Materials such  as Are Used  in Nuclear  Engineering”. These were presented at the Manchester college of Science and Technology on April 12, 1962 by the lubrication and Wear Group of The Institute of Mechanical Engineers (British).   

Power Take off Tractor Lubrication

Farm  tractors  from  different  sources  employ  various  types  of power  take off  devices. Therefore, a common recommendation cannot be given for lubrication of such equipment. In  order to  regulate  the  speed  of the  PTO  independently  of the  speed  of the  tractor, clutches  or a  different  set  of gears  may be   used. With  gears  alone, the grade  and type  of gear oil used  for the tractor  transmission may  be  encountered  and in this  case  ATF  may  be  used. The best  procedure is not  depend  upon  the  recommendations  of the  supplier  of  the  machine.

Garden Tractors and Gear Lubrication

The gears in most garden tractors can be lubricated with engine oil. This should preferably be at least an SAE 30 in weight. Any classification of automotive oil available will be satisfactory. At the end of the season the gear case should be drained and refilled with fresh oil.

  

Transmission and Axle lubrication

Since  the  lubrication of  transmissions  and axles  is  of  primary  importance  in  automotive vehicles, as gearing  is  concerned, this subject  will have first  consideration.  Mention of the lubrication of other gear sets in such vehicles   will then follow:

Also the major discussion will consider internal combustion engines as a source of power. Other  sources  of power  and methods other  than  gearing  for  driving  vehicles and the    consequent fluids  require  will also  receive  mention. Gearing  or  transmission  mechanisms  of automobiles, buses or  trucks  are  lubricated, in the  main , by  bath  or  splash  systems  with some   use of  forced  feed. The gear  cases are  generally  as small  as  possible  so that  consequently  the amount  of gear  oil  present  is  restricted. While  the fluids  present  in gear  boxes  may have  other uses, the primary  functions  are  to  prevent  wear  of gears  and to  act  as a  heat  transfer   medium. The  general  subject of wear  prevention  has been  discussed  previously  and  may  be  due  either  to  the  oil film  alone  or to  this fluid  supplemented by EP  films. The  oil  in gear  cases  of  vehicles takes  up heat  from  the  moving  gears  and transfers  it to the  inside  of the casing. Form here it is dissipated to the surrounding air. Such  radiation is not  always  what  is  desired  because  the gear  housing  becomes  coated  with  dust  or  dirt. Consequently, particularly  in  heavy  trucks  and  busses, the  temperature of the  lubricant may  reach  250  to 300  degree F  causing  excessive oil  deterioration.

 The  loads, speeds,  conditions of use and the  operators  of  vehicles  vary  so  widely  that  it is a wonder  that  automotive  gears  give such  long  and  trouble  free  operation as they  do in  most cases. The service  obtained  from such  gearing is  probably more of a  tribute  to the people who  formulated and  supplied   the  lubricants than  to the  designers  of  the  mechanisms. In fact Raymond, a few years  ago, stated: “ The  hypoid  axle  is easily  the hardest  working  and possibly  one  of the most  neglected   automotive  components”. Elsewhere  the  thought  was  advanced that gear  oil  manufacturers have been  asked to  perform  miracles, in order to lubricates  such  gears.

  

Thickeners for gear oils

The use of thickeners in gear lubricants is not common:  hence, little space need be devoted to the subject. Where lubricating  greases  are  used  in gear sets,  soap  is  normally  the thickener  and  hence will  be  present. In  gear  housings  which  are not  tight, grease will  stay  in  place better  than  will  oil. Later  some  specific  applications  will be  mentioned  where  lubricating  greases are  employed, and  in  such  cases  the  type  of thickener   present will  be  evident.

Resins, both natural and synthetic, are occasionally recommended as thickeners in gear lubricants. Thus, resins separated from Pennsylvania residua are so used. Likewise, certain  grades of  polyethylene  are  thought  to  have not  only  thickening  power  but  also  to  contribute  film  strength  to  lubricants.

Inorganic solids, which  were  previously  mentioned as  being  used  in  gear oils  because of their EP  characteristics, have some  thickening  power  but  are  normally  used  in such  low  proportions that  bodying  is  not  evident. However, fine  silica  is a  component  of  some  semi fluid lubricating  greases  used  in   gear  cases  which  are not  tight and thus would  show  abnormal  leakage  with  fluids. 

Power Steering Gear Fluids

As a base for such a fluids, a solvent refined oil of about 250 viscosity SUS at 100 degree F may be used. While , as Johnson and Mortensen state, the major requirements are shear  stability  and high  V.I., the oil should  also  be  resistant  to oxidation and  have no  adverse effects on both metals  and  seal and  hose  materials. Likewise the blended oil should have a low pour point. All of the above point to a solvent refined oil which will have the desired high V.I. and aniline number.

Chrysler MS 3590 “Hydraulic Steering Fluid with Rust Preventive”, summarizes the composition requirements as follows:

“Well refined oil with admixture of proper rust preventive additives. Small amounts of oxidation inhibitor and pour depressant may also be used to meet the details requirements. The use of   detergents and V.I. improvers is prohibited. The additives small be selected to have a minimum effect on the seal and hose materials”.

Therefore, additives may  include up to 0.5 per cent  of an  oxidation inhibitor, such as  can be  recommended  by  an  additive supplier, or  may  be  phenyl  alpha napththylamine , 2,6-ditertbutyl – 4- methyl  phenol, mixtures  of these  two  types, or  an oil-soluble  organic thiophosphate salt of certain  metals, such  as zinc  methylphenyl  dithiophosphate.

If the pour point of the oil is above -20 degree F, from 0.2 to 1 per cent of a pour depressant, such as “Acryloid  150”, “Paraflow”, or “ Santopour C”, can be added.

Suitable rust inhibitors, used in concentrations of 0.5 to 2 per cent, include petroleum or synthetic sulfonates, such as “Petronate” or barium dinonyl naphthalene sulfonate. A combination oxidation and rust inhibitor, which is usually used in a concentration of 1 per cent or less, is “Vanlube 76”. 

Electromagnetic Transmissions

This type of transmission seems to have little connection with gear oils but since this is a method of transmitting energy in automotive drives, it will be mentioned. It is said that such a coupling, incorporated in an automatic transmission, is being offered as optional equipment in Hillman Minx cars. Magnetized iron particles bind two plates of a clutch to transmit power.

Allied to the above may be what Biryukov describes as an electromagnetic lubricant. This lubricant used to transmit mechanical  energy  by  friction, consists  of 30 per cent of a  medium  viscosity  oil, 4  per cent  of  rosin, 5 per cent of Paratone  and 61 per cent of iron carbonyl . The iron carbonyl should have a particle size of 8 to 13 microns.