WHAT WE DO

Glossary of Terms

Hardness: the resistance of a substance to surface abrasion.

Head: an end closure for the filter case or bowl which contains one or more ports.

Heat exchanger: a device which transfers heat through a conducting wall from one fluid to another.

Heavy Ends: The portions of a petroleum distillate fraction which are highest boiling, and therefore distill over last if the temperature is raised progressively.

Housing: a ported enclosure which directs the flow of fluid through the filter element.

HVI: High Viscosity Index, typically from 80 to 110 VI units.

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 motor: A device which converts hydraulic fluid power into mechanical force and motion by transfer of flow under pressure. It usually provided rotary mechanical motion.

Hydraulic Oil: an oil specially suited for use as either the specific gravity or the API gravity of a liquid.

Hydraulic pump: A device which converts mechanical force and motion into hydraulic fluid power by means of producing flow.

Hydraulic system : A system designed to transmit power through a liquid medium, permitting multiplication of force in accordance with Pascal’s law, which stated that “a pressure exerted on a confined liquid is transmitted undiminished in all directions and acts with equal force on all equal areas.” Hydraulic systems have six basic components: (1) a reservoir to hold the fluid supply; (2) a fluid to transmit the power; (3) a pump to move the fluid; (4) a valve to regulate pressure; (5) a directional valve to control the flow, and (6) a working component – such as a cylinder and piston or a shaft rotated by pressurized fluid – to turn hydraulic power into mechanical motion. Hydraulic systems offer several advantages over mechanical systems: They eliminate complicated mechanisms such as cams, gears, and levers; are less subject to wear; are usually more easily adjusted for control of speed and force; are easily adaptable to both rotary and liner transmission of power; and can transmit power over long distances and in any direction with small losses.

Hydraulics: engineering science pertaining to liquid pressure and flow.

Hydrocarbons: compounds containing only carbon and hydrogen. Petroleum consists chiefly of hydrocarbons.

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.

Hydrogenation: In refining, the chemical addition of hydrogen to a hydrocarbon in the presence of a catalyst; a severe form of hydrogen treating. Hydrogenation may be either destructive or non-destructive. In the former case, hydrocarbon chains are ruptured (cracked) and hydrogen is added where the breaks have occurred. In the latter, hydrogen is added to a molecule that is unsaturated with respect ot hydrogen. In either case, the resulting products are highly stable. Temperatures and pressures in the hydrogenation process are usually greater than in hydrofining.

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.

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.

Hypoid Gears: Gears in which the pinion axis intersects the plane of the ring gear at a point below the ring-gear 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.