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TERMS REL RELATING TING TO THE PETROLEUM INDUSTRY A B C D E F G H I j k L M N O P
H Heat Transfer Oil A medium used for the transfer of heat. Herschel Demulsibility Number A number which indicates the ability of an oil to separate from water under conditions specified by the Herschel Demulsibility Test. Humidity Cabinet Test A test used to evaluate the rust-preventing properties of metal preservatives under conditions of high humidity (ASTM Method D 1748). Hydrocarbon A compound containing only hydrogen and carbon. The simplest hydrocarbons are gases at ordinary temperatures; but with increasing molecular weight, they change to the liquid form and, finally, to the solid state. They form the principal constituents of petroleum. Hydrodynamic (fluid film) Lubrication An oil film which provides a pressure equal to the load. This pressure enables the moving parts to float on a layer of lubricant. Hydrogenation The chemical addition of hydrogen to a material. In non-destructive hydrogenation, hydrogen is added to a molecule only if, and where, unsaturation with respect to hydrogen exists. In destructive hydrogenation, the operation is carried out under conditions which result in rupture of some of the hydrocarbon chains (cracking); hydrogen is added where the chain breaks have occurred. Hypoid Gears Gears in which the pinion axis intersects the plane of the ring gear at a point below the ringgear axle and above the outer edge of the ring gear, or above the ring-gear axle and below the outer edge of the ring gear.
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