Gear lubricants specifications

The lubrication requirements of gears vary considerably and create the need for specifically formulated products. This, combined with the diversity of automotive and industrial gear types, has led to the introduction of several specifications for gear lubricants (see Figure 52.7). 

AGM A specifications covering gear lubricants. The viscosity ranges of the AGMA numbers conform to the International Standards Organization (ISO) viscosity classification system (see ISO viscosity classification system). AGMA numbers and their viscosity ranges are as follows ... 

Figure 7 shows the f(A) function for different values of gear pitch line velocity and as a function of the lubricant specific film thickness. 

Industrial and automotive lubricants are custom-formulated for various types of vehicle engines (depending on specified requirements from engine manufacturers and end users), drivelines (such as transmissions and gear) and industrial equipment (hydraulic, transformers, compressors) [1, 2]. It is not the intention here to cover the large variety of lubricant formulations in specifically chemical terms, as this area of science and technology is appropriately covered in lubrication-specific reviews and monographs. However, a snapshot of the most important lubricant formulation information in terms of its electrochemical properties is presented below. 

For industrial gears and circulating oils there is a specification published by the American Gear Manufacturers Association, which expresses the viscosities corresponding to the AGMA Lubricant Numbers in Saybolt Universal Seconds only. The approximate viscosities in centistokes are provided in Table 52.4 for convenience. The recommendations in Tables 52.5 and 52.6 are intended as a guide for lubricant selection. 

To satisfy the specific needs of these applications, numerous detergent and dispersant substrates have been developed. The aim of this chapter is to highlight the synthesis and utility of the most industrially important of these. Emphasis will be given to engine lubricants since this application has the largest commercial demand for detergents and dispersants. But other key areas, such as gear oils, transmission fluids and fuels, are also considered. 

API GL-2 Lubricants intended for automotive worm gear axles operating under such conditions of load, temperature and sliding velocity that lubricants satisfying API GL-1 service will not suffice. Products suited for this type of service contain anti-wear additives or film-strength improvers specifically designed to protect worm gears. 

The API SM specification, set out in Table 17.9, has mainly similar aims to that of CJ-4. The differences are that the CJ-4 heavy duty diesel specification has a major pre-occupation with the effect of combustion soot-induced thickening of the oil arising from relatively recently introduced environmentally associated emission controls, whereas API SM uses the ASTM sequences IIIG and IIIGA to measure the ability of the lubricant formulation to withstand (mainly) oxidative thickening. Phosphorus and sulphur content limits of lubricant formulations are set. The major part of the API SM specification is concerned with in-cylinder component and valve gear wear. 

CPChem s Synfluid PAO 25 cSt, which is produced with the ionic liquid catalyst has a viscosity at 100 °C, which is unique to the industry. Prior to this product, a 25 cSt PAO was only available commercially by blending higher and lower viscosity PAOs. The specific applications for this product are typically gear oils, greases and various industrial lubricants. 

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