LUBRICATION AND RELIABILITY HANDBOOK pdf

[...]... solvent extracted and dewaxed distillate It should be noted, however, that in Table 2.5 viscosity index has been determined from dynamic viscosities by the method of Roelands, Blok and Vlugter,1 since this is a more fundamental system and allows truer comparison between mineral oils Except for low viscosity oils, when DVIs are higher than KVIs, there is little difference between KVI and DVI for mineral... paraffinic groups (% CP ), and the total number (RT ) of naphthenic and aromatic rings (RN and RA ) joined together Table 2.3 presents examples on a number of typical oils Table 2.3 Typical structural group analyses (courtesy: Institution of Mechanical Engineers) REFINING used as such on some plain bearings subject to high temperatures and as blending components in oils and greases to form very viscous... service by: oxidation, thermal decomposition, and contamination Temperature Oxygen access Catalysis Oxidation Mineral oils are very stable relative to fatty oils and pure hydrocarbons This stability is ascribed to the combination of saturated and unsaturated hydrocarbons and to certain of the hydrocarbon derivatives, i.e compounds containing oxygen, nitrogen and sulphur atoms – the socalled ‘natural inhibitors’... sliding on a film-covered disc Applicable to MoS2 , WS2 and related materials, but not to PTFE and graphite No well-defined trend exists between film life and substrate hardness Molybdenum is usually an excellent substrate for MoS2 films Generally similar trends with film thickness and load also apply to soft metal films A5.2 Solid lubricants and coatings D A5 BONDED COATINGS MoS2 resin coatings show... ‘natural inhibitors’ Top-up rate Oil type Table 2.6 Effects of oxidation and methods of test A2.5 Rate doubles for every 8–10°C temperature rise Degree of agitation of the oil with air Particularly iron and copper in finely divided or soluble form Replenishment of inhibition (natural or added) Proportions and type of aromatics and especially on the compounds containing nitrogen, oxygen, sulphur Mineral... hard insoluble products Plain mineral oils are used in many units and systems for the lubrication of bearings, gears and other mechanisms where their oxidation stability, operating temperature range, ability to prevent wear, etc., are adequate Nowadays, however, the requirements are often greater than plain oils are able to provide, and special chemicals or additives are ‘added’ to many oils to improve... tendency is to use softer greases In centralised lubrication systems, it is unusual to use a grease stiffer than NLGI 2 and often a grease as soft as an NLGI 0 may be found best The extremes (000, 00, 0 and 4, 5, 6) are rarely, if ever, used in normal rolling bearings (other than 0 in centralised systems), but these softer greases are often used for gear lubrication applications GREASE SELECTION When... oxygen and sulphur contents The distillates and residues may be used alone or blended together Additionally, minor amounts of fatty oils or of special oil-soluble chemicals (additives) are blended in to form additive engine oils, cutting oils, gear oils, hydraulic oils, turbine oils, and so on, with superior properties to plain oils, as discussed below The tolerance in blend viscosity for commercial branded... Mineral oils CLASSIFICATION Traditional use Mineral oils are basically hydrocarbons, but all contain thousands of different types of varying structure, molecular weight and volatility, as well as minor but important amounts of hydrocarbon derivatives containing one or more of the elements nitrogen, oxygen and sulphur They are classified in various ways as follows Dating from before viscosity could be measured... classified as lubricants but are Refining processes The distillates and residues are used to a minor extent as such, but generally they are treated or refined both before and after vacuum distillation to fit them for the more stringent requirements The principal processes listed in Table 2.4 are selected to suit the type of crude oil and the properties required Elimination of aromatics increases the .