The best lubricant in the world will fail to accomplish its purpose if it fails to be present on the moving surfaces when required and in the proper amount. Therefore, it should be kept in mind that method of application is as important as the product used. Lubricants may be applied to gearsets and auxiliary mechanisms either manually or mechanically. Hand application is seldom practiced except in the case of exposed gears. Minor exceptions to this rule will be found in the case of small mechanisms, couplings, etc; where most often lubricating greases are added by hand, either upon installation of the equipment or at very infrequent intervals. Mechanical application may take the form of bath, drip, splash, or forced feed. The latter method may simply involve a stream of oil but most often will be in the form of jets or spray, fog or mist.
Normally one thinks of gear lubrication in terms of fluids but an occasional situation will permit or require either a lubricating grease or a solid.
The manufacturer of equipment will generally provide a method for application of gear lubricants, but sometimes the user of a machine will consider a change in lubrication methods. Therefore, enough detail of each method of application will follow to permit selection of the most desirable.
The most important factor in a lubricating system is reliability because failure to supply lubricant will cause damage to machinery . This then points to automatic gear lubrication which is more certain than hand lubrication. Another factor to consider is cost. Circulating oil systems entail a high first cost as they are usually complex. Hand application devices cost little but there is a possibility that use of this method of application may lead to higher maintenance charges than if the lubrication were automatic. Where an oil is used on a once-through basis, as in hand application, a less expensive oil may be used than in bath, splash, or circulating lubrication. Cleanliness, which carries with it less fire hazard, greater safety, and reduced possibility of damage to material being processed, is best obtained by enclosed systems of gear lubrication. While automatic methods of gear lubrication are the most efficient and reliable of the systems mentioned, such devices require some attention to see that a proper supply of uncontaminated oil is available and that the feed is properly adjusted.
Further, installation of a particular type of a lubricating system does not necessarily mean that this will function as desired. While some problems which may be encountered will be mentioned, either when different methods of application are described or in a future chapter devoted to problems, there is often greater possibility that the trouble is mechanical rather than due to the means of application. Therefore, a correction of a gear lubrication problem may be a step- by step process, such as that described by Gesdorf^21 when an automatic spray system was developed for open gears. When and if unsatisfactory lubrication of gears occurs and an automatic system is involved, the best procedure is to bring in both the oil supplier and the manufacturer of the lubricating equipment.
