Types of Lubricants

As load is increased and relative speed is decreased, the film between the two surfaces becomes thinner, and increasing contact occurs between the surface regions. The coefficient of friction rises from the very low values possible for fluid friction to some value that usually is less than that for unlubricated surfaces. This type of lubrication, that is, where the nature of the surface region is... 

Rust inhibitors usually are corrosion inhibitors that have a high polar attraction toward metal surfaces and that form a tenacious, continuous film which prevents water from reaching the metal surface. Typical mst inhibitors are amine succinates and alkaline-earth sulfonates. Rust inhibitors can be used in most types of lubricating oils, but factors of selection include possible corrosion of nonferrous metals or formation of emulsions with water. Because mst inhibitors are adsorbed on metal surfaces, an oil can be depleted of its mst inhibitor. In certain cases, it is possible to correct the depletion by adding more inhibitor. 

In the manufac ture of packings, the proper grade and type of lubricant is usually impregnated for each seiwice tor which the packing i... 

In addition, detailed analysis of the chemical and physical properties of different oils used in the plant can, in some cases, allow consolidation or reduction of the number and types of lubricates required to maintain plant equipment. Elimination of unnecessary duplication can reduce required inventory levels and therefore maintenance costs. 

This chapter examines the need for lubrication and the types of lubricant available. Various applications are considered, including engines gears, hydraulic equipment, machine tools, metal cutting and working fluids, compressors, turbines and electrical oils. The care of lubricants on-site, application of planned lubrication and inclusion within overall maintenance management are examined. 

Boundary lubrication is perhaps best defined as the lubrication of surfaces by fluid films so thin that the friction coefficient is affected by both the type of lubricant and the nature of the surface, and is largely independent of viscosity. A fluid lubricant introduced between two surfaces may spread to a microscopically thin film that reduces the sliding friction between the surfaces. The peaks of the high spots may touch, but interlocking occurs only to a limited extent and frictional resistance will be relatively low. 

This type of lubrication provides the answer to why many mechanisms operate under conditions that are beyond the limits forecast by theory. It was previously thought that increasing pressure reduced oil film thickness until the aspirates broke through, causing metal-to-metal contact. Research has shown, however, that the effect on mineral oil of high contact pressure is a large increase in the viscosity of the lubricant. This viscosity increase combined with the elasticity of the metal causes the oil film to act like a thin solid film, thus preventing metal-to-metal contact. 

Drives incorporating over-running clutches as backstopping devices should be referred to the clutch manufacturers, because certain types of lubricants may adversely affect clutch performance. 

Class Types of lubricant Viscosity grade no. BS 4231) Typical application Detailed application Remarks... 

Class Type of lubricant Consistency number Typical application Detailed application... 

The investigations on boundary lubrication used to focus on the friction elements made of metallic materials, and of steel in particular. This is, of course, due to the fact that a great majority of machines are built from metal and steel, but it is also because the hydrocarbon-based oils have been proven to be an extraordinarily good lubricant for metal surfaces. Unfortunately, the conventional oils are not so effective to lubricate the components made of other materials, like ceramics, rubbers, silicon, etc., so that the study on new types of lubricants suitable for such materials has attracted great attention in recent years. 

Figure 36 shows the contact ratios measured for different types of lubricant, at the speed ranging from 0.13 to 62... 

We performed SPEM studies on hard disc coupons covered with lubricant films of different types and thicknesses [70]. No evidence of dewetting was observed with films of submonolayer average thickness (17 A for Zdol and 14 A for Zdol-TX). Dewetting was observed, however, when the film thickness was above one monolayer. The stracture of these films during dewetting differs depending on the type of lubricant. 

Line shaft may be open or enclosed. Open line shafting is lubricated by the pumped liquid. When pumped liquid is not suitable as a lubricant, enclosed line shafting may be provided to ensure a clean lubrication supply for hue shaft bearings. The type of lubrication will be specified by the purchaser. 

Line shafts may be open or enclosed. For enclosed line shafts the type of lubrication shall be approved by the purchaser. 

A large, immediate increase in the friction coefficient, similar to water application, that follows with a slow decrease in the friction coefficient. These agents can be interpreted to act by immediate hydration of the skin through some aqueous means to give the immediate increase in friction. In Figure 32.4, creams A, B, and C represent this type of lubricant/moisturizer. 

There are three types of lubricants employed in solid dosage form manufacture. The first class of lubricant is the glidant. The flow properties of a powder can be enhanced by the inclusion of a glidant. These are added to overcome powder cohesiveness. The two other classes of lubricant are antiadherent excipients, which reduce the friction between the tablet punch faces and tablet punches, and die wall lubricant excipients, which reduce the friction between the tablet surface and the die wall during and after compaction to enable easy ejection of the tablet. The level of a lubricant required in a tablet is formulation dependent and can be optimized using an instrumented tableting machine. 

There are three types of lubricants added to the powders in order to deal with possible tabletting problems ... 

Although petroleum products had been used earlier, their use only became important from the middle of the nineteenth century. They then slowly revolutionised lubrication because of their effectiveness, stability, availability and cheapness, and because of the wide range of viscosity grades which could be easily produced. Vegetable oils and animal fats continued to be used as alternatives, especially where there was a need for high load-carrying capacity or low friction, but otherwise little effort was made to find other types of lubricant for many years. 

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