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Glossary
Definitions:
A B C
D E F G
H I J K
L M N O
P Q R S
T U V W
X Y Z
Abbreviations Organizations
H
- 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 Transfer Oil
- A medium used for the transfer of heat.
- Heat exchanger
- A device which transfers heat through a conducting wall from one fluid
to another.
- Heavy End Oil
- Highest boiling portion in a distilled petroleum fraction or finished product.
- Herschel Demulsibility Number
- A number which indicates the ability of an oil to separate from water
under conditions specified by the Herschel Demulsibility Test.
- Horsepower
- Unit of power equal to 33,000 foot-pounds per minute, equivalent to 745.7 watts.
- Housing
- A ported enclosure which directs the flow of fluid through the filter
element.
- Humidity Cabinet Test
- A test used to evaluate the rust-preventing properties of metal preservatives
under conditions of high humidity (ASTM Method D 1748).
- 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 as either the specific gravity or
the API gravity of a liquid.
- 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
- 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.
- 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.
- Hydrophilic
- Having an affinity for water.
- Hydrophobic
- Lacking an affinity for water.
- 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.
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