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Galling -- a form of wear in which seizing or tearing of the gear or bearing surface occurs. Gas chromatography (GC) -- is a method of measuring the volatile chemical constituents of a substance. This test is used to determine the quality, identity and purity of every essential oil. GC analysis produces a usable profile of the oil by showing the quantitative presence of each chemical compound. Gasohol -- a blend of 10% anhydrous ethanol (ethyl alcohol) and 90% gasoline, by volume. Used as a motor fuel. Gear oil -- a high-quality oil with good oxidation stability, load-carrying capacity, rust protection, and resistance to foaming, for service in gear housing and enclosed chain drives. Specially formulated industrial EP gear oils are used where high loaded gear sets or excessive sliding actions are encountered. Generated contaminant -- caused by a deterioration of critical wetted surfaces and materials or by a breakdown of the fluid itself. Graphite -- a crystalline form of carbon having a laminar structure, which is used as a lubricant. It may be of natural or synthetic origin. Gravimetric analysis -- a method of analysis whereby the dry weight of contaminant per unit volume of fluid can be measured showing the degree of contamination in terms of milligrams of contaminant per litre of fluid. Gravity -- see Specific Gravity; API Gravity. Grease -- a mixture of a lubricating oil and a thickener (soap or non-soap) to produce a solid to semi-liquid (semi-fluid) lubricant. Soap thickeners are formed by reacting (saponifying) a metallic hydroxide with a fat, fatty acid, or ester. The type of soap (i.e. Lithium, Calcium, Aluminum) used depends on the grease properties desired. A complex-soap is formed by the reaction of an alkali with a high-molecular-weight fat or fatty acid to form a soap, and the simultaneous reaction of the alkali with a short chain organic or inorganic acid to form a metallic salt (the complexing agent). Non-Soap thickeners such as clays, silica gels, carbon black, and various other synthetic organic materials are also used. Hardness -- the resistance of a substance to surface abrasion. Heat exchanger -- a device which transfers heat through a conducting wall from one fluid to another. High Speed Viscometer (HSV) -- is a cost effective, fast and accurate automatic viscometer designed for oil analysis laboratories to test a wide range of lubricant viscosities and is available from the Fluid Life Corporation. Housing -- a ported enclosure which directs the flow of fluid through the filter element. Hydraulic fluid -- fluid serving as the power transmission medium in a hydraulic system. The most commonly used fluids are petroleum oils, synthetic lubricants, oil-water emulsions, and water-glycol mixtures. The principal requirements of a premium hydraulic fluid are proper viscosity, high viscosity index, anti-wear protection (if needed), good oxidation stability, adequate pour point, good demulsibility, rust inhibition, resistance to foaming, and compatibility with seal materials. Anti-wear oils are frequently used in compact, high-pressure, and capacity pumps that require extra lubrication protection. Hydraulic oil -- an oil specially suited for use in hydraulic applications and typically contains anti-wear(AW) additives. Hydraulics -- engineering science pertaining to liquid pressure and flow. Hydrocarbons -- compounds containing only carbon and hydrogen. Petroleum consists chiefly of hydrocarbons. Hydrocracking -- a process used in petroleum refining involving the cracking or thermal degradation of petroleum in the presence of hydrogen and a catalyst to produce products. Hydrodynamic lubrication -- a system of lubrication in which the shape and relative motion of the sliding surfaces causes the formation of a fluid film having sufficient pressure to separate the surfaces. Hydrofinishing -- a process for treating raw extracted base stocks with hydrogen to saturate them for improved stability. Hydrolysis -- breakdown process that occurs in anhydrous hydraulic fluids as a result of heat, water, and metal catalysts (iron, steel, copper, etc.) Hydrolytic stability -- ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water. Hydrometer -- an instrument for determining either the specific gravity of a liquid or the API gravity. Hydrostatic lubrication -- a system of lubrication in which the lubricant is supplied under sufficient external pressure to separate the opposing surfaces by a fluid film. Hydrotreating -- a process used to make higher quality lubricant base stocks. In the process a lubricant feedstock is reacted with hydrogen and a catalyst at high temperature and pressure. The process removes un-saturated hydrocarbons and impurities. Hypoid gear -- a type of spiral level gear with non-intersecting shafts crossing at right angles. Hypoid gear lubricant -- a gear lubricant having extreme pressure characteristics for use with a hypoid type of gear as in the differential of an automobile.
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