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.

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.     

Wheel Type Tractors and their Gear Lubrication

According to  Caterpillar, transmissions of a  few  models of wheel  type  tractors  require series  3 motor oils in an  SAE  30  grade above 32 degree F  and  in an  SAE  10W   grade  for  lower  starting  atmospheric  temperatures. The  transmission  lubricant  suggested  for  most  models of  wheel  type tractors  is a multipurpose type  gear oil conforming to MIL-L-2105. An  SAE 90  grade  is  recommended for  starting  temperatures above 32 degree F and  an  SAE 80  grade  for lower  temperatures. Below -10 degree F it may be necessary to dilute this latter grade with kerosene.

The  same MIL-L-2105 type of gear oil  and like  grades  are  suggested  for all models of wheel  tractor differential  and final  drive  compartments. It is recommended that transmission oil filters be changed every   250 hours, except in the case of three models where the period is 500 hours. The  suggested  oil  change  period  for both  transmission  and differential  and final drive  compartments  of wheel  type  tractors is 1000 hours.

 Similar tractors of other makes, as well as allied equipment, such as motor grades etc., will probably require similar types and grades of gear lubricants. However, it is better to follow instructions furnished by the equipment manufacturer or supplier.

Troubles Connected with venting of gear cases

Vents are necessary on practically all gear cases. However, such openings may lead to trouble. Thus, with  a  humid  atmosphere and  considerable  change  in  temperatures  of  gear  boxes, moisture will  enter and  condense, thereby  increasing  the possibility of rusting. Also dirt may enter through such openings. On  automobile  manufacturer actually  experienced  the  entrance of  both  dirt  and moisture  through the vents  in  differential  housings. The  correction was  to  extend  a house  from  the  vent  forward  with  the open  end  placed  on the frame, under  the  body and  facing  toward  the side  of  the car. A location for  the  opening  was chosen where  the  least  throw off from  the  tires  would  the present. If  the  intake  of  dust  or  dirt  is  material, the  use of air  filters is  suggested. Such precautions are taken in the case of machines operating in very dusty atmospheres. Thus, most tractors use filters on vents of gear cases. However, this adds another problem in that such filters must be kept clean. Suggestions have been  made  that  gear  cases  be kept  under  slight  pressure, thus  preventing  entrance of  contaminants. However, this is impractical in most cases. Installation of  filters  containing  silica  gel  on  vents  from  gear boxes has  been  suggested. While this would remove moisture, the value would depend upon the frequency of renewal of the absorbent. 

   

Potato chip Production and gear lubrication

The production of  potato  chips illustrates  food  handling  where  the gears  concerned are so  located that  little  contamination from the  lubricant  is possible. Numerous conveyors will be found for the potatoes, the slices, or the packages. Most of the gear reducers  for  conveyors will  be  subjected  to  only  moderate   temperatures  and not too  much  stress. Hence, either  straight  mineral  oil  or  MP  lubricant  of SAE  80  grade  can be used  for  the gears.

 If  a batch  peeler is used,  this may consist of  a  vertical  cylinder with  a rotating  abrasive  disc in the  bottom  which  will  be  driven  by  gears. Also, in washing potato slices, a gear driven drum will probably be used. The gear oil mentioned above will also serve these latter applications.  

Lubrication of starter Gears in vehicles

The perimeter of the flywheel has gear teeth which are engaged by the starter. Since the use of  this  gearing is very  intermittent, a little  multipurpose  lubricating  grease  at  long  intervals  will provide  sufficient  lubrication.

Motorcycle Gear Lubrication

While  some  models  of  motorcycles  recommend  special  motorcycle oil, the  transmission  of such  vehicles  often  use  the  heavier  grades  of  crankcase  oils. For low temperatures, SAE 30 or in some cases SAE 20W oil is suggested and for higher temperatures SAE 40 or 50. The recommendations of the  manufacturer  should  be  noted  and  followed  both as to  grade  and quantity  of transmission  oil. In at least one instance  the transmission is combined with the crankcase.

Truck Transmission and Differential Lubricants

Truck gears, in the main, require higher viscosity oils than do the gears in passenger cars. However, it is difficult to generalize since any one manufacturer of trucks may employ a variety of methods of speed reduction as well as perhaps more than one type of differential. However, lubrication charts are kept up to date and such charts, as well as the recommendations of the truck manufacturer should be consulted as to the proper grade and type of gear lubricant to use. Lubricating charts should be read with care because blanket recommendations are not made for all trucks of a given make. Also footnotes  are  frequently used  to  provide additional  or  more  detailed  information about  truck gear  oils.

A number of truck manufacturers depend upon specialty companies to provide them with transmissions or axles. In this case the parts manufacturer may suggest the most satisfactory gear lubricant. These firms often issue. Field maintenance Manuals devoted to each type of speed reduction unit or each type of axle. Such manuals generally contain sections on lubrication.

Almost all truck distributors suggest some variation in the viscosity of gear oils used as the temperatures change. A blanket statement cannot be made, but sometimes above 32 degree F an  SAE 140  grade of  lubricant  will be  recommended and  below this  an SAE 90.

While it has  been pointed out that lubrication would be  simplified by the use of a common  lubricant  for  transmission and  axles of  trucks,  there is not  an  agreement on this. Thus, Nelson and  Valentine^40 mention that a rear axle  lubricant must be  capable  of  absorbing  greater  torque  or providing  better  load  carrying  qualities  than  a  transmission, particularly  in  the  first  three gears.

Fletcher^19  notes that  many fleets have  standardized on the use of  engine oils in transmissions and  cites  a large  bus line which has used  SAE 30  and  modified SAE 10 engine  oils in  transmissions  for  many  years. The 30  grade is used  in straight mechanical boxes  and  the 10  grade  when mechanical  transmissions are  combined with  a  converter or coupling  and  a common  oil  supply  is  required for  the  two  units. This author objects to the oxidation and sludging of EP oils compared to straight mineral oils. His suggestion is the use of SAE 50 oil for transmissions. Another argument in  favor of  the  engine oils  is that  in  corrosion tests, using bronze specimens, such oils showed  little corrosion whereas  both  HP and  MP  oils  showed excessive corrosion.

On the other hand, Calish^8 cites evidence of the practicality of the use of a common transmission and axle lubricant in heavy equipment. A specific additive oil composition was used in some 1420 vehicles representing sixteen makes of trucks. The inference is that such a uniform transmission and axle lubricant proved satisfactory to the thirty-four accounts operating the above trucks over a period of several years.

When transfer cases are used to drive various devices, the same grade and type of oil as is  used  in the  transmission case will be satisfactory. Transfer  case  is a term applied to gear assemblies which transfer  power from  the  main  drive  line to  auxiliary equipment such  as  front wheel  drives, pulleys, hydraulic pumps, windlasses, and other mechanisms. For example,  many heavy  duty utility  vehicles carry winches for  erecting  heavy poles, devices for  boring holes  in  the  earth, and  other tools which  must  be  driven from  the  same  power source.

Where trucks  are  equipped  with  automatic  transmissions, ATF is  satisfactory  for use  and is so  listed in most  lubrication charts. However,  as a  matter  of  economy, General Motors  suggests the  use  of a  Hydraulic transmission Fluid, type C for  certain heavy duty trucks, buses, and  earth- moving  vehicles. Type C does not  have all  the  characteristics of  ATF  but  does  have  to  pass a  Powerglide Transmission Test, have  low  varnish and  sludge  deposits, and  must have  a  minimum effect  on rubber  seals. This Type C should never be substituted for ATF where the latter is specified.

Truck  Axle Lubricants. There seems to be little question as to the necessity of EP gear oils in axles of heavy duty trucks. However, there is not  common agreement as to  the  proper  grade  or  viscosity  of  lubricant  for  such  applications. Johnson^27, who considered these subjects, states:

“ Our  field experience is quite  conclusive to  the  effect  that  an SAE-140  viscosity lubricant is  far  superior to an SAE-90 in  its  ability  to  prevent gear wear  and  related  problems. On  numerous occasions  we have been  able  to  overcome  gear  wear  problems by  merely  effecting  a change  from  an SAE-90 to an SAE-140 viscosity”.

Also, it was found  that, with the heavier gear oil, temperatures in the  gear  case  did not  increase  but actually were  5 to  10 degree F lower than when  operating  with  the  lower  viscosity oil. The use of SAE 250  gear  oil  was  investigated but  it  was  found  that  this did run hotter  than  the SAE 140 grade.

A  further  advantage  of  the  use  of the higher  viscosity oil was found  by  this  investigator^27 when  the two  grades of hypoid lubricants were tested  on  eighteen driven units in the laboratory, using hypoid gears with a  61/6 ratio. The results obtained were:

“At 3000 rpm, the SAE-140 lubricant supported a torque load 21% greater than the SAE-90. At 2500 rpm, the advantage was 23%, and at 2000 rpm, it was 20%”.

Another factor, indicating the desirability of higher viscosity oils in axles of trucks, is that pointed out by Blok^3. It  was  mentioned that,  under  conditions of  impact  load  on  gears, viscosity is of  prime importance and  that  this  property of the oil  cannot  be  replaced by  antiwelding  activity  if wear  is to be  prevented.

Gears in  heavy duty trucks are  subjected to  low  speeds  and  high  torque conditions during much  of  their operation. For example, Nelson and  Valentine^40 determined that  in  highway operation a truck having  a 5-speed transmission used first speed about 2 per cent of the time, second  speed about 3 per cent, and  third speed  about 10 per cent , or a total of  15 per cent. The resulting comment was: “It is in this interval that gear destruction is prevalent, if the lubricant does not have proper EP qualities”. Further, mention is  made  that  in  off -high way  service, such trucks  operate approximately 50 per cent of the  time  in  the  first  three transmission gears.

Not all EP gear oils will provide satisfactory protection to axle gears operating at low speeds, and high torque, as do those in trucks. Therefore,  assurance  should be  obtained that  lubricants satisfactory for  such service  are  used  for  truck  axles. Lead soap active sulfur EP lubricants have been favored by some for such application. Since the  prevalent operation of  passenger cars is  under  high  speed  and  low  torque conditions, it is  desirable that a single  type  gear  oil  satisfy these conditions as well as  those  of  operating trucks. With this in mind, what is considered by some as a truly multipurpose gear lubricant has been provided? Such oils are those  conforming  to  specification MIL-L-2105B  which  is accepted  for  the  requirements of  all  vehicles operated by  the  U.S Military and by  many  other  users.

Some axle manufacturers and truck producers prefer to  either issue specifications for  what  they  know to be  satisfactory  axle lubricants or  to  state the type of EP  gear oil  to  employ. Hence, it is well to abide by the opinion of the truck supplier when choosing lubricants for truck axles.

This is all the more true because the gearing in truck axles may vary. Most  of  such variations, with  the exception of worm  drives, will probably  require  the  same  type  and  grade of  gear  oil as will  straight  hypoid  gears.  Thus, Rockwell  standard for  either  Planetary Axles or Hypoid- Helical  Two- Speed Double-Reduction Drive Units, as  well as  Spiral Bevel Gears,  recommend oils conforming to  their  Standard 0-65, which  is  an  SAE 140  EP  product. Use of Standard 0-65, the SAE 90 grade is optional but is suggested for lower operating temperatures than the 0-65.

Lubrication of Worm Drives on Trucks. In the case of worm drives on trucks, recommendations for the lubricant vary. While some suppliers of EP gear lubricants claim such oils can be used safely in worm drives, Watson^51 states:

“Actually, in practice, an EP lubricant is usually unnecessary for a worm gear. When lubrication failure occurs in a  rear-axle worm gear, only  in  exceptional  circumstances can it be  attributed  to  lack  of load carrying capacity  of the  oil used”.

Certainly  if temperatures  exceed 200 degree F, as they  may  at  times in axles of any  large  vehicle, EP additives may  cause  excessive corrosion of  bronze. Since EP agents and combinations of the same cover such a wide range of chemical compounds, the above statement may require modification. Perhaps the worst offenders are sulfur compounds, even some not considered active at 200 degree F. The possible  explanation may  be  that since  copper has  considerable affinity  for  sulfur, temperatures at  contact  points  of  the  gear  and worm  will  be  high  enough  to  cause  reduction of the  metal and sulfur. That, is the action may be akin to temperature flashes which occur with hypoid gears.

However, substitutions  have been  made for  recommended worm gear  lubricants; and if this  is done, fleet operators  are in a  better position to  observe result  than are  individual vehicle operators. In  certain  busses of  the  London Transport Company  having worm  drives, it  was  reasoned that  a fuel saving would be possible if there was less  drag due  to  the  axle lubricant. An  exceptionally thin oil  gave  satisfactory lubrication, but  when  changing from  first  to second gear  on  a level road, the  lay shaft  spun so  freely  that  the  higher gear  could  not  be  engaged until the  bus  came  to rest. An inhibited castor oil was then tried and proved satisfactory. However, the operation of these  specific  vehicles with  considerable stop  and start does  not  result  in  heating of the axle  lubricant, with  a consequent  possibility of oxidation, as would be the  case  in over-the –road vehicles.

While possible variations in oils for servicing worm gears of trucks have been mentioned, this is for information only. The safest  course  for  the  owner or  user  of  such a truck  is to follow the  recommendations of  the  manufacturer  of the  equipment.

Viscosity Temperature Characteristics of Gear Lubricants

Since gear and transmission oils are subjected to widely varying temperatures, particularly in vehicles, it is desirable that such lubricants have as little change in viscosity with temperature changes as is possible. In other words, high V.I. oils are desirable in many gear oil applications and absolutely necessary in certain cases. An illustration of the latter is automatic transmission fluid. Base oils with V.I. values of 90 to 95 are readily available when needed. Where it is desired to increase the V.I. of oil, additives, known as V.I. improvers, are sometimes used. These agents are generally  polymers  which act by either coiling  up or  becoming less  soluble  at  low temperatures but reverse  this action as temperatures  increase,  so as to  contribute increasing body at higher temperatures. In normal gear  operation the shearing  effect  tends to break  down such polymers  into those  of lower molecular weight  which  are  less  effective  as V.I. improvers. However, these agents do have a place in services such as ATF where they maintain their effectiveness.

Certain  high molecular weight  petroleum resins  have been found to improve  the V.I. of some lubricating  oils  and  not  have  the defect  of  breakdown with  shear.

Desirable low and high temperature qualities of gear oils

Transmission and gear oils which are used either in vehicles or in outside locations in cold climates should remain fluid at low temperatures. Low temperature is a relative term and an extreme case is that of aircraft flying at high altitudes which, therefore, encounter temperatures approaching – 70 degree (F). The gear oils used in this case are compounded from synthetic fluids.

Disregarding synthetic lubricating fluids, two general types of mineral oils are available. These are naphthenic and paraffin. The former, as a rule has the best cold test because no wax is present, but as temperatures are reduced such oils may tend to become quite viscous. This tendency will vary both with the viscosity and the source of the base oil. Most paraffin type oils contain wax which crystallizes at low temperatures and may therefore form a solid mass which will not flow or pump and may even channel in a gear case so that the gear teeth would lack a lubricant. By the addition of pour depressants, generally certain  types of  polymers, the wax crystals are coated  so  that in place  of growing to long  needles  thy deposit as fine crystals which produce a slurry  which moves at a lower temperature  than the untreated oil.

A more positive approach to securing low cold test gear oil is to choose lubricating oil which has been refined so as to have a low pour point. Low viscosity oils generally have lower cold tests than high viscosity oils of the same type. Thus, lubricating oils are available with viscosity of 70 to 80 SUS at 100 degree (F) which have pour points of -60 to -70 degree (F). Proper dewaxing will also lower pour points. In extreme cases gear oils are offered which consist of lubricating oils diluted with fractions boiling below the lubricating fractions. Likewise, in the arctic regions Kerosene has been used to dilute gear oils. This poses a  hazard to the equipment  if the diluted  lubricant  is not removed  from  the  gear  case  with the advent  of normal temperatures.

High temperature limitations of most gear oils will be due to deterioration of the oil and additives. Oils should be chosen having high flash points if operating temperatures are excessive. The flash point of oil is generally indicative of the temperature at which volatility starts. In most industrial gear applications, the bulk oil temperature seldom exceeds 125 to 150 degree (F). In vehicles such temperatures seldom exceed 300 degree (F). Therefore, for  what considered normal  gear lubrication, additives are  selected  with  the  thought  that  temperatures of  use  will  not exceed 300 degree(F)

However, Borsoff et al ^8 describes tests run at both 400 degree (F) and 600 degree(F) on a  gear test  machine in which the gear compartment and the oil were  heated while  the machine  was in operation. Conclusions drawn from this investigation were:

                                   “Due to the thermal instability of the lubricants, the operation of gears for any prolonged period of time at 600 degree (F) or higher is inadvisable; (2) no new or unusual types of failures were observed during the operations of gears at 400degree (F) and 600degree (F). Just as at normal operating temperatures, scoring and abrasion were the two primary destructive failures; (3) the load carrying capacities of oils decreased with the increase in temperature. However, at temperatures over 400degree (F) gum deposits are formed by oils. These deposits serve as a protective coating and improve scoring performance of gears and gear lubricants”. For this reason SAE 20 and SAE 30 mineral oils and “Plexol 201” showed about the same load carrying capacity at 400degree (F) as at 100 degree (F). However, 1010 grade and SAE 60 mineral oils, “Ucons LB-170” and 50-HB-170 and “DC-200” silicone fluid all scored at lower loads at 400degree (F) than at 100 degree (F).

Bowden and Tabor^11 investigated the frictional behavior of oil films on steel surfaces as they were heated and as oxidation took place. At 302 degree (F) after 30 minutes heating the friction became low. At 392 degree (F) the reduction in friction occurred after 15 minutes heating and at 572 degree (F) low friction was observed after less than 2 minutes heating. In the latter case if heating was continued for 20 minutes a thick gum was formed and  friction increased to a high value. The above action was no doubt due to the formation of acidic products due to oxidation. Such products, in time, might lead to corrosive wear. Next the oil would increase in viscosity and compounds would from which are insoluble in the oil. When and if acidic products result from heating of gear oils, metal compounds will eventually from and these in turn will act as catalysts to promote further oxidation.

In view of the fact that high temperatures cause rapid deterioration of most gear lubricants, equipment should be so designed that operating gears are subjected to only moderate temperatures if long life of gear oils is expected.

However, since the military  desire gear lubricants for  jet aircraft  and  other agencies for space vehicles which  will stand  very  high  temperatures, it can be  expected that synthetic fluids or solids will  be  available  which will withstand 700 degree (F) or even 1000 degree(F) for a period.

Compatibility of gear oils

Gear lubricants consisting of straight mineral oils will mix in all proportions at normal ambient temperatures. The resulting physical characteristics of the mixtures will not be an exact proportional average but will approximate this.   

On the other hand, gear lubricants containing additives may be changed either chemically or physically by mixing those of different compositions. For example, some EP additives have limited solubility in high V.I. oils. If then such additives are blended with naphthenic oils which will hold them in suspension and such blends in turn are mixed with high V.I. oils, a portion of the additive might settle out of the mixture. Also, if gear oil containing lead soap were mixed with such oil containing an active sulfur compound, a precipitate of lead sulfide might be formed. Compatibility of gear lubricants is of little concern in industrial service where either the life of the lubricant is long or, if additional oil is required in a gear case, it will likely be from the same source. However, in automotive equipment the necessity of compatibility of gear oils is important because vehicles may be serviced by distributers handling different brands of oil than that originally used in the gear cases. Recognizing the possibility of mixtures of gear oils from various sources U.S. Government agencies have the following requirement in most gear lubricant specifications: “the lubricant shall be compatible with each of the other lubricants qualified under this specification.”Commercial multi-purpose gear oils are almost universally compatible with each other.