| Abrasion
a general wearing away of a surface
by constant scratching, usually due to the presence
of foreign matter such as dirt, grit, or metallic particles
in the lubricant. It may also cause a break down of
the material such as the tooth surfaces of gears. Lack
of proper lubrication may result in abrasion
Abrasive wear or cutting
wear comes about when hard surface asperities or hard
particles that have embedded themselves into a soft
surface and plough grooves into the opposing harder
surface, e.g., a journal.
Absolute filtration rating diameter
of the largest hard spherical particle that will pass
through a filter under specified test conditions. This
is an indication of the largest opening in the filter
elements.
Absolute Viscosity a term
used interchangeably with viscosity to distinguish it
from either kinematic viscosity or commercial viscosity.
Absolute viscosity is the ratio of shear stress to shear
rate. It is a fluid's internal resistance to flow. The
common unit of absolute viscosity is the poise. Absolute
viscosity divided by fluid density equals kinematic
viscosity. It is occasionally referred to as dynamic
viscosity. Absolute viscosity and kinematic viscosity
are expressed in fundamental units. Commercial viscosity
such as Saybolt viscosity is expressed in arbitrary
units of time, usually seconds.
Absorbent filter a filter
medium that holds contaminant by mechanical means.
Absorption the assimilation
of one material into another; in petroleum refining,
the use of an absorptive liquid to selectively remove
components from a process stream.
AC Fine Test Dust (ACFTD) A
test contaminant used to assess both filters and the
contaminant sensitivity of all types of tribological
mechanisms.
Accumulator a container
in which fluid is stored under pressure as a source
of fluid power.
Acid in a restricted sense,
any substance containing hydrogen in combination with
a nonmetal or nonmetallic radical and capable of producing
hydrogen ions in solution.
Acidity in lubricants, acidity
denotes the presence of acid-type constituents whose
concentration is usually defined in terms of total acid
number. The constituents vary in nature and may or may
not markedly influence the behavior of the lubricant.
Additive a compound that
enhances some property of, or imparts some new property
to, the base fluid. In some hydraulic fluid formulations,
the additive volume may constitute as much as 20 percent
of the final composition. The more important types of
additives include anti-oxidants, anti-wear additives,
corrosion inhibitors, viscosity index improvers, and
foam suppressants.
Additive stability the ability
of additives in the fluid to resist changes in their
performance during storage or use.
Adhesion the property of
a lubricant that causes it to cling or adhere to a solid
surface.
Adhesive wear is often referred
to as galling, scuffing, scoring, or seizing. It happens
when sliding surfaces contact one another, causing fragments
to be pulled from one surface and to adhere to the other.
Adsorbent filter a filter
medium primarily intended to hold soluble and insoluble
contaminants on its surface by molecular adhesion.
Adsorption adhesion of the
molecules of gases, liquids, or dissolved substances
to a solid surface, resulting in relatively high concentration
of the molecules at the place of contact; e.g. the plating
out of an anti-wear additive on metal surfaces.
Adsorptive filtration the
attraction to, and retention of particles in, a filter
medium by electrostatic forces, or by molecular attraction
between the particles and the medium.
Aeration the state of air
being suspended in a liquid such as a lubricant or hydraulic
fluid.
A.G.M.A. abbreviation for
"American Gear Manufacturers Associations,"
an organization serving the gear industry.
Agglomeration -- the potential
of the system for particle attraction and adhesion.
Air, Compressed -- air at
any pressure greater than atmospheric pressure.
Air Breather -- a device
permitting air movement between atmosphere and the component
in/on which it is installed.
Alkali -- any substance having
basic (as opposed to acidic) properties. In a restricted
sense it is applied to the hydroxides of ammonium, lithium,
potassium and sodium. Alkaline materials in lubricating
oils neutralize acids to prevent acidic and corrosive
wear in internal combustion engines.
Analytical ferrography - the
magnetic precipitation and subsequent analysis of wear
debris from a fluid sample This approach involves passing
a volume of fluid over a chemically treated microscope
slide which is supported over a magnetic field. Permanent
magnets are arranged in such a way as to create a varying
field strength over the length of the substrate. This
varying strength causes wear debris to precipitate in
a distribution with respect to size and mass over the
Ferrogram. Once rinsed and fixed to the substrate, this
debris deposit serves as an excellent media for optical
analysis of the composite wear particulates.
Anhydrous -- devoid of water.
Anti-foam agent -- one of
two types of additives used to reduce foaming in petroleum
products: silicone oil to break up large surface bubbles
, and various kinds of polymers that decrease the amount
of small bubbles entrained in the oils.
Anti-friction bearing a
rolling contact type bearing in which the rotating or
moving member is supported or guided by means of ball
or roller elements. Does not mean without friction.
Anti-oxidants prolong the
induction period of a base oil in the presence of oxidizing
conditions and catalyst metals at elevated temperatures.
The additive is consumed and degradation products increase
not only with increasing and sustained temperature,
but also with increases in mechanical agitation or turbulence
and contamination -- air, water, metallic particles,
and dust.
Antistatic additive an additive
that increases the conductivity of a hydrocarbon fuel
to hasten the dissipation of electrostatic charges during
high-speed dispensing, thereby reducing the fire/explosion
hazard.
Antiwear additives -- improve
the service life of tribological elements operating
in the boundary lubrication regime. Antiwear compounds
(for example, ZDDP and TCP) start decomposing at 90°
to 100°C and even at a lower temperature if water (25
to 50 ppm) is present.
API engine service categories -- gasoline
and diesel engine oil quality levels established jointly
by API, SAE, and ASTM, and sometimes called SAE or API/SAE
categories; formerly called API Engine Service Classifications.
API gravity -- a gravity
scale established by the American Petroleum Institute
and in general use in the petroleum industry, the unit
being called "the A.P.I. degree." This unit
is defined in terms of specific gravity as follows:
API ° =
(141.5 ÷ specific gravity at 60/60°F) − 131.5
The notation 60/60°F specifies a density measured
at 60°F and referenced to water at 60°F. The density
of water at one atmosphere and 60°F is 62.368 lbm/ft3
or 999.04 kg/m3.
Ash -- a measure of the amount
of inorganic material in lubricating oil. Determined
by burning the oil and weighing the residue. Results
expressed as percent by weight.
Asperities -- microscopic
projections on metal surfaces resulting from normal
surface-finishing processes. Interference between opposing
asperities in sliding or rolling applications is a source
of friction, and can lead to metal welding and scoring.
Ideally, the lubricating film between two moving surfaces
should be thicker than the combined height of the opposing
asperities.
A.S.T.M. = American Society for Testing Materials"
-- a society for developing standards
for materials and test methods.
Atomic absorption spectroscopy -- measures
the radiation absorbed by chemically unbound atoms by
analyzing the transmitted energy relative to the incident
energy at each frequency. The procedure consists of
diluting the fluid sample with methyl isobutyl ketone
(MIBK) and directly aspirating the solution. The actual
process of atomization involves reducing the solution
to a fine spray, dissolving it, and finally vaporizing
it with a flame. The vaporization of the metal particles
depends upon their time in the flame, the flame temperature,
and the composition of the flame gas. The spectrum occurs
because atoms in the vapor state can absorb radiation
at certain well-defined characteristic wave lengths.
The wave length bands absorbed are very narrow and differ
for each element. In addition, the absorption of radiant
energy by electronic transitions from ground to excited
state is essentially and absolute measure of the number
of atoms in the flame and is, therefore, the concentration
of the element in a sample.
Automatic Transmission Fluid (ATF) -- fluid for automatic, hydraulic transmissions in motor vehicles.
Axial-load bearing -- a bearing
in which the load acts in the direction of the axis
of rotation.
Babbitt -- a soft, white,
non-ferrous alloy bearing material composed principally
of copper, antimony, tin and lead.
Bactericide -- additive included
in the formulations of water-mixed cutting fluids to
inhibit the growth of bacteria promoted by the presence
of water, thus preventing odors that can result from
bacterial action.
Ball bearing -- an antifriction
rolling type bearing containing rolling elements in
the form of balls.
Barrel -- a unit of liquid
volume of petroleum oils equal to 42 U.S.
gallons or approximately 35 Imperial gallons.
Base -- a material which
neutralizes acids. An oil additive containing colloidally
dispersed metal carbonate, used to reduce corrosive
wear.
Base stock -- the base fluid,
usually a refined petroleum fraction or a selected synthetic
material, into which additives are blended to produce
finished lubricants.
Bearing -- a support or guide
by means of which a moving part such as a shaft or axle
is positioned with respect to the other parts of a mechanism.
Beta Rating -- the method
of comparing filter performance based on efficiency.
This is done using the Multi-Pass Test which counts
the number of particles of a given size before and after
fluid passes through a filter.
Beta-Ratio (ß-Ratio) -- the
ratio of the number of particles greater than a given
size in the influent fluid to the number of particles
greater than the same size in the effluent fluid, under
specified test conditions (see "Multi-Pass Test").
Bitumen -- also called asphalt
or tar, bitumen is the brown or black viscous residue
from the vacuum distillation of crude petroleum. It
also occurs in nature as asphalt "lakes" and
"tar sands." It consists of high molecular
weight hydrocarbons and minor amounts of sulfur and
nitrogen compounds.
Black oils -- lubricants
containing asphaltic materials, which impart extra adhesiveness,
that are used for open gears and steel cables.
Blow-by -- passage of unburned
fuel and combustion gases past the piston rings of internal
combustion engines, resulting in fuel dilution and contamination
of the crankcase oil.
Boundary lubrication -- form
of lubrication between two rubbing surfaces without
development of a full-fluid lubricating film. Boundary
lubrication can be made more effective by including
additives in the lubricating oil that provide a stronger
oil film, thus preventing excessive friction and possible
scoring. There are varying degrees of boundary lubrication,
depending on the severity of service. For mild conditions,
oiliness agents may be used; by plating out on metal
surfaces in a thin but durable film, oiliness agents
prevent scoring under some conditions that are too severe
for a straight mineral oil. Compounded oils, which are
formulated with polar fatty oils, are sometimes used
for this purpose. Anti-wear additives are commonly used
in more severe boundary lubrication applications. The
more severe cases of boundary lubrication are defined
as extreme pressure conditions; they are met with lubricants
containing EP additives that prevent sliding surfaces
from fusing together at high local temperatures and
pressures.
Breakdown maintenance -- maintenance
performed after a machine has failed to return it to
an operating state.
Bridging -- a condition of
filter element loading in which contaminant spans the
space between adjacent sections of a filter element,
thus blocking a portion of the useful filtration.
Bright stock -- a heavy residual
lubricant stock with low pour point, used in finished
blends to provide good bearing film strength, prevent
scuffing, and reduce oil consumption. Usually identified
by its viscosity, SUS at 210°F or cSt at 100°C.
Brinelling -- permanent deformation
of the bearing surfaces where the rollers (or balls)
contact the races. Brinelling results from excessive
load or impact on stationary bearings. It is a form
of mechanical damage in which metal is displaced or
upset without attrition.
Brookfield viscosity --
apparent viscosity in cP determined
by Brookfield viscometer, which measures the torque required to rotate
a spindle at constant speed in oil of a given temperature.
Basis for ASTM Method D 2983; used for measuring low
temperature viscosity of lubricants.
BTU -- British thermal unit.
The amount of heat required to raise the temperature
of 1 pound of water 1 degree Fahrenheit.
Bubble point -- the differential
gas pressure at which the first steady stream of gas
bubbles is emitted from a wetted filter element under
specified test conditions.
Built-in-dirt -- Material
passed into the effluent stream composed of foreign
materials incorporated into the filter medium.
Bulk modulus (of elasticity) -- a
ratio of normal stress to a change in volume. A term
used in determining the compressibility of a fluid.
Data for petroleum products can be found in the International
Critical Tables.
Burst pressure rating -- the
maximum specified inside-out differential pressure that
can be applied to a filter element without outward structural
or filter-medium failure.
Bushing -- a short, externally
threaded connector with a smaller size internal thread.
Bypass Filtration -- a system
of filtration in which only a portion of the total flow
of a circulating fluid system passes through a filter
at any instant or in which a filter having its own circulating
pump operates in parallel to the main flow.
Bypass valve (Relief valve) -- a
valve mechanism that assures system fluid flow when
a preselected differential pressure across the filter
element is exceeded; the valve allows all or part of
the flow to bypass the filter element.
Cams -- eccentric shafts
used in most internal combustion engines to open and
close valves.
Capacity -- the amount of
contaminants a filter will hold before an excessive
pressure drop is caused. Most filters have bypass valves
which open when a filter reaches its rated capacity.
Capillarity -- a property
of a solid-liquid system manifested by the tendency
of the liquid in contact with the solid to rise above
or fall below the level of the surrounding liquid; this
phenomenon is seen in a smallbore (capillary) tube.
Carbon -- a non-metallic
element - No. 6 in the periodic table. Diamonds and
graphite are pure forms of carbon. Carbon is a constituent
of all organic compounds. It also occurs in combined
form in many inorganic substances; i.e., carbon dioxide,
limestone, etc.
Carbon residue -- coked material
remaining after an oil has been exposed to high temperatures
under controlled conditions.
Carbonyl iron powder -- a
contaminant which consists of up to 99.5% pure iron
spheres.
Case drain filter -- a filter
located in a line conducting fluid from a pump or motor
housing to reservoir.
Catalyst -- a substance which
speeds a chemical action without undergoing a chemical
change itself during the process. Now used in catalytic
converters to control amount of unburned hydrocarbons
and CO in automobile exhaust.
Catalytic converter -- an
integral part of vehicle emission control systems since
1975. Oxidizing converters remove hydrocarbons and carbon
monoxide (CO) from exhaust gases, while reducing converters
control nitrogen oxide (NOx) emissions. Both use noble
metal (platinum, palladium or rhodium) catalysts that
can be "poisoned" by lead compounds in the
fuel or lubricant.
Catastrophic failure -- sudden,
unexpected failure of a machine resulting in considerable
cost and downtime.
Cavitation -- formation of
an air or vapor pocket (or bubble) due to lowering of
pressure in a liquid, often as a result of a solid body,
such as a propeller or piston, moving through the liquid;
also, the pitting or wearing away of a solid surface
as a result of the collapse of a vapor bubble. Cavitation
can occur in a hydraulic system as a result of low fluid
levels that draw air into the system, producing tiny
bubbles that expand explosively at the pump outlet,
causing metal erosion and eventual pump destruction.
Cavitation erosion -- a material-damaging
process which occurs as a result of vaporous cavitation.
"Cavitation" refers to the occurrence or formation
of gas- or vapor- filled pockets in flowing liquids
due to the hydrodynamic generation of low pressure (below
atmospheric pressure). This damage results from the
hammering action when cavitation bubbles implode in
the flow stream. Ultra-high pressures caused by the
collapse of the vapor bubbles produce deformation, material
failure and, finally, erosion of the surfaces.
Cellulose Media -- a filter
material made from plant fibers. Because cellulose is
a natural material, its fibers are rough in texture
and vary in size and shape. Compared to synthetic media,
these characteristics create a higher restriction to
the flow of fluids.
Centipoise (cp) -- a unit
of absolute viscosity. 1 centipoise = 0.01 poise.
Centistoke (cst) -- a unit
of kinematic viscosity. 1 centistoke = 0.01 stoke.
Centralized lubrication -- a
system of lubrication in which a metered amount of lubricant
or lubricants for the bearing surfaces of a machine
or group of machines are supplied from a central location.
Centrifugal separator -- a
separator that removes immiscible fluid and solid contaminants
that have a different specific gravity than the fluid
being purified by accelerating the fluid mechanically
in a circular path and using the radial acceleration
component to isolate these contaminants.
Chemical stability -- the
tendency of a substance or mixture to resist chemical
change.
Chip control (grit control, last-chance) filter
-- a filter intended to prevent only large particles from entering a
component immediately downstream.
Circulating lubrication -- a
system of lubrication in which the lubricant, after
having passed through a bearing or group of bearings,
is recirculated by means of a pump.
Cleanable -- a filter element
which, when loaded, can be restored by a suitable process,
to an acceptable percentage of its original dirt capacity.
Clean room -- a facility
or enclosure in which air content and other conditions
(such as temperature, humidity, and pressure) are controlled
and maintained at a specific level by special facilities
and operating processes and by trained personnel.
Cleanliness level (CL) -- a
measure of relative freedom from contaminants.
Clearance bearing -- a journal
bearing in which the radius of the bearing surface is
greater than the radius of the journal surface.
Cloud point -- the temperature
at which waxy crystals in an oil or fuel form a cloudy
appearance.
Coalescor -- a separator
that divides a mixture or emulsion of two immiscible
liquids using the interfacial tension between the two
liquids and the difference in wetting of the two liquids
on a particular porous medium.
Coefficient of friction -- the
number obtained by dividing the friction force resisting
motion between two bodies by the normal force pressing
the bodies together.
Cohesion -- that property
of a substance that causes it to resist being pulled
apart by mechanical means.
Cold cranking simulator (CCS) -- an
intermediate shear rate viscometer that predicts the
ability of an oil to permit a satisfactory cranking
speed to be developed in a cold engine.
Collapse -- an inward structural
failure of a filter element which can occur due to abnormally
high pressure drop (differential pressure) or resistance
to flow.
Collapse pressure -- the
minimum differential pressure that an element is designed
to withstand without permanent deformation.
Compound -- (1) chemically
speaking, a distinct substance formed by the combination
of two or more elements in definite proportions by weight
and possessing physical and chemical properties different
from those of the combining elements. (2) in
petroleum processing, generally connotes fatty oils
and similar materials foreign to petroleum added to
lubricants to impart special properties.
Compounded oil -- a petroleum
oil to which has been added other chemical substances.
Compressibility -- the change
in volume of a unit volume of a fluid when subjected
to a unit change of pressure.
Compression ratio -- in an
internal combustion engine, the ratio of the volume
of combustion space at bottom dead center to that at
top dead center.
Compressor -- a device which
converts mechanical force and motion into pneumatic
fluid power.
Consistency -- the degree
to which a semisolid material such as grease resists
deformation. (See ASTM designation D 217.) Sometimes
used qualitatively to denote viscosity of liquids.
Contaminant -- any foreign
or unwanted substance that can have a negative effect
on system operation, life or reliability.
Contaminant (Dirt, ACFTD) capacity -- the
weight of a specified artificial contaminant that must
be added to the influent to produce a given differential
pressure across a filter at specified conditions. Used
as an indication of relative service life.
Contaminant Failure -- any
loss of performance due to the presence of contamination.
Two basic types of contamination failure are: Perceptible
-- gradual loss of efficiency or performance, and
Catastrophic -- dramatic, unexpected failure.
Contaminant lock -- a particle
or fiber-induced jam caused by solid contaminants.
Contamination control -- a
broad subject which applies to all types of material
systems (including both biological and engineering).
It is concerned with planning, organizing, managing,
and implementing all activities required to determine,
achieve and maintain a specified contamination level.
Coolant -- a fluid used to
remove heat. See Cutting fluid.
Copper strip corrosion -- a
qualitative measure of the tendency of a petroleum product
to corrode pure copper.
Core -- the internal duct
and filter media support.
% Correl -- the percentage
of peaks in the used oil infrared spectrum which match
those in the reference oil. A sudden decrease in this
value usually means that the oil was mixed with a different
type.
Corrosion -- the decay and
loss of a metal due to a chemical reaction between the
metal and its environment. It is a transformation process
in which the metal passes from its elemental form to
a combined (or compound) form.
Corrosion inhibitor -- additive
for protecting lubricated metal surfaces against chemical
attack by water or other contaminants. There are several
types of corrosion inhibitors. Polar compounds wet the
metal surface preferentially, protecting it with a film
of oil. Other compounds may absorb water by incorporating
it in a water-in-oil emulsion so that only the oil touches
the metal surface. Another type of corrosion inhibitor
combines chemically with the metal to present a non-reactive
surface.
Coupling, quick disconnect -- a
coupling which can quickly join or separate lines.
Coupling -- a straight connector
for fluid lines.
Cracking -- the process whereby
large molecules are broken down by the application of
heat and pressure to form smaller molecules.
Crown -- the top of the piston
in an internal combustion engine above the fire ring,
exposed to direct flame impingement.
Cryogenics -- the branch
of physics relating to the production and effects of
very low temperatures.
Cutting fluid -- any fluid
applied to a cutting tool to assist in the cutting operation
by cooling, lubricating or other means.
Cycle -- a single complete
operation consisting of progressive phases starting
and ending at the neutral position.
Cylinder -- a device which
converts fluid power into linear mechanical force and
motion. It usually consists of a moveable element such
as a piston and piston rod, plunger rod, plunger or
ram, operating with in a cylindrical bore.
Deaerator -- a separator
that removes air from the system fluid through the application
of bubble dynamics.
Degas -- removing air from
a liquid, usually by ultrasonic and/or vacuum methods.
Degradation -- the progressive
failure of a machine or lubricant.
Dehydrator -- a separator
that removes water from the system fluid.
Delamination wear -- a complex
wear process where a machine surface is peeled away
or otherwise removed by forces of another surface acting
on it in a sliding motion.
Demulsibility -- the ability
of a fluid that is insoluble in water to separate from
water with which it may be mixed in the form of an emulsion.
Density -- the mass of a
unit volume of a substance. Its numerical value varies
with the units used.
Deposits -- oil-insoluble
materials that result from oxidation and decomposition
of lube oil and contamination from external sources
and engine blow-by. These can settle out on machine
or engine parts. Examples are sludge, varnish, lacquer
and carbon.
Depth filter -- a filter
medium that retains contaminants primarily within tortuous
passages.
Desorption -- opposite of
absorption or adsorption. In filtration, it relates
to the downstream release of particles previously retained
by the filter.
Detergent -- in lubrication,
either an additive or a compounded lubricant having
the property of keeping insoluble matter in suspension
thus preventing its deposition where it would be harmful.
A detergent may also redisperse deposits already formed.
Dielectric Strength -- a
measure of the ability of an insulating material to
withstand electric stress (voltage) without failure.
Fluids with high dielectric strength (usually expressed
in volts or kilovolts) are good electrical insulators.
(ASTM Designation D 877.)
Differential pressure indicator -- an
indicator which signals the difference in pressure between
any two points of a system or a component.
Dirt capacity (dust capacity) (contaminant
capacity) -- the weight of a specified artificial contaminant which must
be added to the influent to produce a given differential
pressure across a filter at specified conditions. Used
as an indication of relative service life.
Dispersant -- in lubrication,
a term usually used interchangeably with detergent.
An additive, usually nonmetallic ("ashless"),
which keeps fine particles of insoluble materials in
a homogeneous solution. Hence, particles are not permitted
to settle out and accumulate.
Disposable -- a filter element
intended to be discarded and replaced after one service
cycle.
Dissolved gases -- those
gases that enter into solution with a fluid and are
neither free nor entrained gases.
Distillation method (ASTM D-95) -- a
method involving distilling the fluid sample in the
presence of a solvent that is miscible in the sample
but immiscible in water. The water distilled from the
fluid is condensed and segregated in a specially-designed
receiving tube or tray graduated to directly indicate
the volume of water distilled.
Drum -- a container with
a capacity of 55 U.S. gallons.
Duplex filter -- an assembly
of two filters with valving for selection of either
or both filters.
Effluent -- the fluid leaving
a component.
Elastohydrodynamic lubrication -- in
rolling element bearings, the elastic deformation of
the bearing (flattening) as it rolls, under load, in
the bearing race. This momentary flattening improves
the hydrodynamic lubrication properties by converting
point or line contact to surface-to-surface contact.
Electrostatic separator -- a
separator that removes contaminant from dielectric fluids
by applying an electrical charge to the contaminant
that is then attracted to a collection device of different
electrical charge.
Element (Cartridge) -- the
porous device that performs the actual process of filtration.
Emission spectrometer -- works
on the basis that atoms of metallic and other particular
elements emit light at characteristic wavelengths when
they are excited in a flame, arc, or spark. Excited
light is directed through an entrance slit in the spectrometer.
This light penetrates the slit, falls on a grate, and
is dispersed and reflected. The spectrometer is calibrated
by a series of standard samples containing known amounts
of the elements of interest. By exciting these standard
samples, an analytical curve can be established which
gives the relationship between the light intensity and
its concentration in the fluid.
Emulsibility -- the ability
of a non-water-soluble fluid to form an emulsion with
water.
Emulsifier -- additive that
promotes the formation of a stable mixture, or emulsion,
of oil and water. Common emulsifiers are: metallic soaps,
certain animal and vegetable oils, and various polar
compounds.
Emulsion -- intimate mixture
of oil and water, generally of a milky or cloudy appearance.
Emulsions may be of two types: oil-in water (where water
is the continuous phase) and water-in-oil (where water
is the discontinuous phase).
End cap -- a ported or closed
cover for the end of a filter element.
Engine deposits -- hard or
persistent accumulation of sludge, varnish and carbonaceous
residues due to blow-by of unburned and partially burned
fuel, or the partial breakdown of the crankcase lubricant.
Water from the condensation of combustion products,
carbon, residues from fuel or lubricating oil additives,
dust and metal particles also contribute.
Environmental contaminant -- all
material and energy present in and around an operating
system, such as dust, air moisture, chemicals, and thermal
energy.
EP (Extreme Pressure) lubricants -- lubricants
that impart to rubbing surfaces the ability to carry
appreciably greater loads than would be possible with
ordinary lubricants without excessive wear or damage.
Erosion -- the progressive
removal of a machine surface by cavitation or by particle
impingement at high velocities.
Extreme pressure (EP) additive -- lubricant
additive that prevents sliding metal surfaces from seizing
under conditions of extreme pressure. At the high local
temperatures associated with metal-to-metal contact,
an EP additive combines chemically with the metal to
form a surface film that prevents the welding of opposing
asperities, and the consequent scoring that is destructive
to sliding surfaces under high loads. Reactive compounds
of sulfur, chlorine, or phosphorus are used to form
these inorganic films.
Fabrication integrity point -- the
differential gas pressure at which the first stream
of gas bubbles are emitted from a wetted filter element
under standard test conditions.
False brinelling -- false
brinelling of needle roller bearings is actually a fretting
corrosion of the surface since the rollers are the I.D.
of the bearing. Although its appearance is similar to
that of brinelling, false brinelling is characterized
by attrition of the steel, and the load on the bearing
is less than that required to produce the resulting
impression. It is the result of a combination of mechanical
and chemical action that is not completely understood,
and occurs when a small relative motion or vibration
is accompanied by some loading, in the presence of oxygen.
Fatigue chunks -- thick three-dimensional
particles exceeding 50 microns indicating severe wear
of gear teeth.
Fatigue platelets -- normal
particles between 20 and 40 microns found in gear box
and rolling element bearing oil samples observed by
analytical ferrography. A sudden increase in the size
and quantity of these particles indicates excessive
wear.
Fatigued -- a structural
failure of the filter medium due to flexing caused by
cyclic differential pressure.
Ferrography -- an analytical
method of assessing machine health by quantifying and
examining ferrous wear particles suspended in the lubricant
or hydraulic fluid.
Film strength -- property
of a lubricant that acts to prevent scuffing or scoring
of metal parts.
Filter -- any device or porous
substance used as a strainer for cleaning fluids by
removing suspended matter.
Filter Efficiency -- method
of expressing a filter's ability to trap and retain
contaminants of a given size.
Filter element -- the porous
device which performs the actual process of filtration.
Filter head -- an end closure
for the filter case or bowl that contains one or more
ports.
Filter housing -- a ported
enclosure that directs the flow of fluid through the
filter element.
Filter life test -- a type
of filter capacity test in which a clogging contaminant
is added to the influent of a filter, under specified
test conditions, to produce a given rise in pressure
drop across the filter or until a specified reduction
of flow is reached. Filter life may be expressed as
test time required to reach terminal conditions at a
specified contaminant addition rate.
Filter media, depth -- porous
materials which primarily retain contaminants within
a tortuous path, performing the actual process of filtration.
Filter media, surface -- porous
materials which primarily retain contaminants on the
influent face, performing the actual process of filtration.
Filtration (Beta) ratio -- the
ratio of the number of particles greater than a given
size in the influent fluid to the number of particles
greater than the same size in the effluent fluid.
Filtration -- the physical
or mechanical process of separating insoluble particulate
matter from a fluid, such as air or liquid, by passing
the fluid through a filter medium that will not allow
the particulates to pass through it.
Fire point (Clevelend Open Cup) -- the
temperature to which a combustible liquid must be heated
so that the released vapor will burn continuously when
ignited under specified conditions.
Fire-resistant fluid -- lubricant
used especially in high-temperature or hazardous hydraulic
applications. Three common types of fire-resistant fluids
are: (1) water-petroleum oil emulsions, in which
the water prevents burning of the petroleum constituent;
(2) water-glycol fluids; and (3) non-aqueous
fluids of low volatility, such as phosphate esters,
silicones, and halogenated hydrocarbon-type fluids.
Flash point (Cleveland Open Cup) -- the
temperature to which a combustible liquid must be heated
to give off sufficient vapor to form momentarily a flammable
mixture with air when a small flame is applied under
specified conditions. (ASTM Designation D 92.)
Flow, laminar -- a flow situation
in which fluid moves in parallel lamina or layers.
Flow, turbulent -- a flow
situation in which the fluid particles move in a random
manner.
Flow fatigue rating -- the
ability of a filter element to resist a structural failure
of the filter medium due to flexing caused by cyclic
differential pressure.
Flow rate -- the volume,
mass, or weight of a fluid passing through any conductor
per unit of time.
Flowmeter -- a device which
indicates either flow rate, total flow, or a combination
of both.
Fluid -- a general classification
including liquids and gases.
Fluid, fire resistant -- a
fluid difficult to ignite which shows little tendency
to propagate flame.
Fluid compatibility -- the
suitability of filtration medium and seal materials
for service with the fluid involved.
Fluid friction -- friction
due to the viscosity of fluids.
Fluid opacity -- related
to the ability of a fluid to pass light.
Fluid power -- energy transmitted
and controlled through use of a pressurized fluid.
Flushing -- a fluid circulation process designed to remove contamination
from the wetted surfaces of a fluid system.
Force feed lubrication -- a
system of lubrication in which the lubricant is supplied
to the bearing surface under pressure.
Fretting -- wear phenomena
taking place between two surfaces having oscillatory
relative motion of small amplitude.
Fretting corrosion -- can
take place when two metals are held in contact and subjected
to repeated small sliding, relative motions. Other names
for this type of corrosion include wear oxidation, friction
oxidation, chafing, and brinelling.
Friction -- the resisting
force encountered at the common boundary between two
bodies when, under the action of an external force,
one body, moves or tends to move relative to the surface
of the other.
FTIR = Fourier Transform Infrared Spectroscopy
-- a test where infrared light absorption is used for assessing levels
of soot, sulfates, oxidation, nitro-oxidation, glycol,
fuel, and water contaminants.
Full flow filter -- a filter
that, under specified conditions, filters all influent
flow.
Full-flow filtration -- a
system of filtration in which the total flow of a circulating
fluid system passes through a filter.
Full-fluid-film lubrication -- presence
of a continuous lubricating film sufficient to completely
separate two surfaces, as distinct from boundary lubrication.
Full-fluid-film lubrication is normally hydrodynamic
lubrication, whereby the oil adheres to the moving part
and is drawn into the area between the sliding surfaces,
where it forms a pressure -- or hydrodynamic -- wedge.
Gage -- an instrument or
device for measuring, indicating or comparing a physical
characteristic.
Galling -- a form of wear
in which seizing or tearing of the gear or bearing surface
occurs.
Gasohol -- a blend of 10%
anhydrous ethanol (ethyl alcohol) and 90% gasoline,
by volume. Used as a motor fuel.
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 lubricant composed
of an oil or oils thickened with a soap, soaps or other
thickener to a semisolid or solid consistency.
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.
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 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.
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.
Image analyzer -- a sophisticated
microscopic system involving a microscope, a television
camera, a dedicated computer, and a viewing monitor
similar to a television screen.
Immiscible -- incapable of
being mixed without separation of phases. Water and
petroleum oil are immiscible under most conditions,
although they can be made miscible with the addition
of an emulsifier.
In-line filter -- a filter
assembly in which the inlet, outlet and filter element
axes are in a straight line.
Indicator -- a device which
provides external evidence of sensed phenomena.
Indicator, pressure -- an
indicator that signals pressure conditions.
Indicator, differential pressure -- an
indicator which signals the difference in pressure between
two points, typically between the upstream and downstream
sides of a filter element.
Influent -- the fluid entering
a component.
Infrared spectroscopy -- an
analytical method using infrared absorption for assessing
the properties of used oil and certain contaminants
suspended therein. See FTIR.
Infrared spectra -- a graph
of infrared energy absorbed at various frequencies in
the additive region of the infrared spectrum. The current
sample, the reference oil and the previous samples are
usually compared.
Ingested contaminants -- environmental
contaminant that ingresses due to the action of the
system or machine.
Ingression level -- particles
added per unit of circulating fluid volume.
Inhibitor -- any substance
that slows or prevents such chemical reactions as corrosion
or oxidation.
Insolubles -- particles of
carbon or agglomerates of carbon and other material.
Indicates deposition or dispersant drop-out in an engine.
Not serious in a compressor or gearbox unless there
has been a rapid increase in these particles.
Intensifier -- a device which
converts low pressure fluid power into higher pressure
fluid power.
Interfacial tension (IFT) -- the
energy per unit area present at the boundary of two
immiscible liquids. It is usually expressed in dynes/cm
(ASTM Designation D 971.)
ISO Solid Contaminant Code (ISO 4406) -- a code assigned on the basis of the number of particles per unit
volume greater than 5 and 15 micrometers in size. Range
numbers identify each increment in the particle population
throughout the spectrum of levels.
ISO Standard 4021 -- the
accepted procedure for extracting samples from dynamic
fluid lines.
ISO viscosity grade -- a
number indicating the nominal viscosity of an industrial
fluid lubricant at 40°C (104°F) as defined by ASTM Standard
Viscosity System for Industrial Fluid Lubricants D 2422.
Essentially identical to ISO Standard 3448.
Journal -- that part of a
shaft or axle that rotates or angularly oscillates in
or against a bearing or about which a bearing rotates
or angularly oscillates.
Journal bearing -- a sliding
type of bearing having either rotating or oscillatory
motion and in conjunction with which a journal operates.
In a full or sleeve type journal bearing, the bearing
surface is 360° in extent. In a partial bearing, the
bearing surface is less than 360° in extent, i.e., 150°,
120°, etc.
Karl Fischer Reagent Method (ASTM D-1744-64)
-- the standard laboratory test to measure the water content of mineral
base fluids. In this method, water reacts quantitatively
with the Karl Fischer reagent. This reagent is a mixture
of iodine, sulfur dioxide, pyridine, and methanol. When
excess iodine exists, electric current can pass between
two platinum electrodes or plates. The water in the
sample reacts with the iodine. When the water is no
longer free to react with iodine, an excess of iodine
depolarizes the electrodes, signaling the end of the
test.
Kinematic viscosity -- the
time required for a fixed amount of an oil to flow through
a capillary tube under the force of gravity. The unit
of kinematic viscosity is the stoke or centistoke (1/100
of a stoke). Kinematic viscosity may be defined as the
quotient of the absolute viscosity in centipoises divided
by the specific gravity of a fluid, both at the same
temperature--
Centipoises / Specific Gravity = Centistokes
Lacquer -- a deposit resulting
from the oxidation and polymerization of fuels and lubricants
when exposed to high temperatures. Similar to, but harder,
than varnish.
Laminar particles -- particles
generated in rolling element bearings which have been
flattened out by a rolling contact.
Lead naphthenate -- a lead
soap of naphthenic acids, the latter occurring naturally
in petroleum.
Light obscuration -- the
degree of light blockage as reflected in the transmitted
light impinging on the photodiode.
Liquid -- any substance that
flows readily or changes in response to the smallest
influence. More generally, any substance in which the
force required to produce a deformation depends on the
rate of deformation rather than on the magnitude of
the deformation.
Load-carrying capacity -- property
of a lubricant to form a film on the lubricated surface,
which resists rupture under given load conditions. Expressed
as maximum load the lubricated system can support without
failure or excessive wear.
Lubricant -- any substance
interposed between two surfaces in relative motion for
the purpose of reducing the friction and/or the wear
between them.
Lubricity -- ability of an
oil or grease to lubricate; also called film strength.
Magnetic -- a separator that
uses a magnetic field to attract and hold ferromagnetic
particles.
Magnetic filter -- a filter
element that, in addition to its filter medium, has
a magnet or magnets incorporated into its structure
to attract and hold ferromagnetic particles.
Magnetic plug -- strategically
located in the flow stream to collect a representative
sample of wear debris circulating in the system: for
example, engine swarf, bearing flakes, and fatigue chunks.
The rate of buildup of wear debris reflects degradation
of critical surfaces.
Manifold -- a filter assembly
containing multiple ports and integral relating components
which services more than one fluid circuit.
Manifold filter -- a filter
in which the inlet and outlet port axes are at right
angles, and the filter element axis is parallel to either
port axis.
Media migration -- material
passed into the effluent stream composed of the materials
making up the filter medium.
Medium -- the porous material
that performs the actual process of filtration. The
plural of this word is "media".
Metal oxides -- oxidized
ferrous particles which are very old or have been recently
produced by conditions of inadequate lubrication. Trend
is important.
Micrometre (µm) -- See Micron.
Micron -- a unit of length.
One Micron = 39 millionths of an inch (.000039").
Contaminant size is usually described in microns. Relatively
speaking, a grain of salt is about 60 microns and the
eye can see particles to about 40 microns. Many hydraulic
filters are required to be efficient in capturing a
substantial percentage of contaminant particles as small
as 5 microns. A micron is also known as a micrometre,
and exhibited as µm
Microscope method -- a method
of particle counting which measures or sizes particles
using an optical microscope.
Mineral oil -- oil derived
from a mineral source, such as petroleum, as opposed
to oils derived from plants and animals.
Miscible -- capable of being
mixed in any concentration without separation of phases;
e.g., water and ethyl alcohol are miscible.
Moly -- Molybdenum disulfide,
a solid lubricant and friction reducer, colloidally
dispersed in some oils and greases.
Motor -- a device which converts
fluid power into mechanical force and motion. It usually
provides rotary mechanical motion.
Multigrade oil -- an oil
meeting the requirements of more than one SAE viscosity
grade classification, and may therefore be suitable
for use over a wider temperature range than a single-grade
oil.
Multipass or recirculation test -- filter
performance tests in which the contaminated fluid is
allowed to recirculate through the filter for the duration
of the test. Contaminant is usually added to the test
fluid during the test. The test is used to determine
the Beta-Ratio (q.v.) of an element.
Naphthenic -- a type of petroleum
fluid derived from naphthenic crude oil, containing
a high proportion of closed-ring methylene groups.
Needle bearing -- a rolling
type of bearing containing rolling elements that are
relatively long compared to their diameter.
Neutralization number -- a
measure of the total acidity or basicity of an oil;
this includes organic or inorganic acids or bases or
a combination thereof (ASTM Designation D974-58T)
Newtonian fluid -- a fluid
with a constant viscosity at a given temperature regardless
of the rate of shear. Single-grade oils are Newtonian
fluids. Multigrade oils are NON-Newtonian fluids because
viscosity varies with shear rate.
Nitration -- nitration products
are formed during the fuel combustion process in internal
combustion engines. Most nitration products are formed
when an excess of oxygen is present. These products
are highly acidic, form deposits in combustion areas
and rapidly accelerate oxidation.
Nominal filtration rating -- an
arbitrary micrometer value indicated by a filter manufacturer.
Due to lack of reproducibility this rating is deprecated.
Non-Newtonian fluid -- fluid,
such as a grease or a polymer-containing oil (e.g.,
multi-grade oil), in which shear stress is not proportional
to shear rate.
Nonwoven medium -- a filter
medium composed of a mat of fibers.
Obliteration -- a synergistic
phenomenon of both particle silting and polar adhesion.
When water and silt particles co-exist in a fluid containing
long-chain molecules, the tendency for valves to undergo
obliteration increases.
Oil -- a greasy, unctuous
liquid of vegetable, animal, mineral or synthetic origin.
Oiliness -- that property
of a lubricant that produces low friction under conditions
of boundary lubrication. The lower the friction, the
greater the oiliness.
Oil ring -- a loose ring,
the inner surface of which rides a shaft or journal
and dips into a reservoir of lubricant from which it
carries the lubricant to the top of a bearing by its
rotation with the shaft.
Open bubble point (boil point) -- the
differential gas pressure at which gas bubbles are profusely
emitted from the entire surface of a wetted filter element
under specified test conditions.
Oxidation -- occurs when
oxygen attacks petroleum fluids. The process is accelerated
by heat, light, metal catalysts and the presence of
water, acids, or solid contaminants. It leads to increased
viscosity and deposit formation.
Oxidation inhibitor -- substance
added in small quantities to a petroleum product to
increase its oxidation resistance, thereby lengthening
its service or storage life; also called anti-oxidant.
An oxidation inhibitor may work in one of these ways:
(1) by combining with and modifying peroxides
(initial oxidation products) to render them harmless,
(2) by decomposing the peroxides, or (3) by rendering
an oxidation catalyst inert.
Oxidation stability -- ability
of a lubricant to resist natural degradation upon contact
with oxygen.
Paper chromatography -- a
method which involves placing a drop of fluid on a permeable
piece of paper and noting the development and nature
of the halos, or rings, surrounding the drop through
time. The roots of this test can be traced to the 1940s,
when railroads used the "blotter spot" tests.
Paraffinic -- a type of petroleum
fluid derived from paraffinic crude oil and containing
a high proportion of straight chain saturated hydrocarbons.
Often susceptible to cold flow problems.
Particle count -- the number
of particles present greater than a particular micron
size per unit volume of fluid often stated as particles
> 10 microns per milliliter.
Particle density -- an important
parameter in establishing an entrained particle's potential
to impinge on control surfaces and cause erosion.
Particle erosion -- occurs
when fluid-entrained particles moving at high velocity
pass through orifices or impinge on metering surfaces
or sharp angle turns.
Particle impingement erosion -- a
particulate wear process where high velocity, fluid-entrained
particles are directed at target surfaces.
Patch test -- a method by
which a specified volume of fluid is filtered through
a membrane filter of known pore structure. All particulate
matter in excess of an "average size," determined
by the membrane characteristics, is retained on its
surface. Thus, the membrane is discolored by an amount
proportional to the particulate level of the fluid sample.
Visually comparing the test filter with standard patches
of known contamination levels determines acceptability
for a given fluid.
Permeability -- the relationship
of flow per unit area to differential pressure across
a filter medium.
pH -- measure of alkalinity
or acidity in water and water-containing fluids. pH
can be used to determine the corrosion-inhibiting characteristic
in water-based fluids. Typically, pH > 8.0 is required
to inhibit corrosion of iron and ferrous alloys in water-based
fluids.
Pinion -- the smaller of
two mating or meshing gears; can be either the driving
or the driven gear.
Pitting -- a form of extremely
localized attack characterized by holes in the metal.
Pitting is one of the most destructive and insidious
forms of corrosion. Depending on the environment and
the material, a pit may take months, or even years,
to become visible.
Pleated filter -- a filter
element whose medium consists of a series of uniform
folds and has the geometric form of a cylinder, cone,
disc, plate, etc. Synonymous with "convoluted"
and "corrugated".
Pneumatics -- engineering
science pertaining to gaseous pressure and flow.
Poise (absolute viscosity) -- a
measure of viscosity numerically equal to the force
required to move a plane surface of one square centimeter
per second when the surfaces are separated by a layer
of fluid one centimeter in thickness. It is the ratio
of the shearing stress to the shear rate of a fluid
and is expressed in dyne seconds per square centimeter
(DYNE SEC/CM2); 1 centipoise equals .01 poise.
Polar compound -- a chemical
compound whose molecules exhibit electrically positive
characteristics at one extremity and negative characteristics
at the other. Polar compounds are used as additives
in many petroleum products. Polarity gives certain molecules
a strong affinity for solid surfaces; as lubricant additives
(oiliness agents), such molecules plate out to form
a tenacious, friction-reducing film. Some polar molecules
are oil-soluble at one end and water-soluble at the
other end; in lubricants, they act as emulsifiers, helping
to form stable oil-water emulsions. Such lubricants
are said to have good metal-wetting properties. Polar
compounds with a strong attraction for solid contaminants
act as detergents in engine oils by keeping contaminants
finely dispersed.
Polishing (bore) -- excessive
smoothing of the surface finish of the cylinder bore
or cylinder liner in an engine to a mirror-like appearance,
resulting in depreciation of ring sealing and oil consumption
performance.
Polymerization -- the chemical
combination of similar-type molecules to form larger
molecules.
Pore -- a small channel or
opening in a filter medium which allows passage of fluid.
Pore size distribution -- the
ratio of the number of effective holes of a given size
to the total number of effective holes per unit area
expressed as a percent and as a function of hole size.
Porosity -- the ratio of
pore volume to total volume of a filter medium expressed
as a percent.
Positive crankcase ventilation (PCV) -- system for removing blow-by gases from the crankcase and returning
them through the carburetor intake manifold to the combustion
chamber where the recirculated hydrocarbons are burned.
A PC valve controls the flow of gases from the crankcase
to reduce hydrocarbon emissions.
Pour point -- lowest temperature
at which an oil or distillate fuel is observed to flow,
when cooled under conditions prescribed by test method
ASTM D 97. The pour point is 3°C (5°F) above the temperature
at which the oil in a test vessel shows no movement
when the container is held horizontally for five seconds.
Pour point depressant -- an
additive which retards the adverse effects of wax crystallization,
and lowers the pour point.
Power unit -- a combination
of pump, pump drive, reservoir, controls and conditioning
components which may be required for its application.
Predictive maintenance -- a
type of condition-based maintenance emphasizing early
prediction of failure using non-destructive techniques
such as vibration analysis, thermography, and wear debris
analysis.
Pressure -- force per unit
area, usually expressed in pounds per square inch.
Pressure, absolute -- the
sum of atmospheric and gage pressures.
Pressure, atmospheric -- pressure
exerted by the atmosphere at any specific location.
(Sea level pressure is approximately 14.7 pounds per
square inch absolute.)
Pressure, back -- the pressure
encountered on the return side of a system.
Pressure, cracking -- the
pressure at which a pressure operated valve begins to
pass fluid.
Pressure, rated -- the qualified
operating pressure which is recommended for a component
or a system by the manufacturer.
Pressure, system -- the pressure
which overcomes the total resistances in a system. It
includes all losses as well as useful work.
Pressure Drop -- Resistance
to flow created by the element (media) in a filter.
Defined as the difference in pressure upstream (inlet
side of the filter) and downstream (outlet side of the
filter).
Pressure gage -- pressure
differential above or below atmospheric pressure.
Pressure line filter -- a
filter located in a line conducting working fluid to
a working device or devices.
Preventive maintenance -- maintenance
performed according to a fixed schedule involving the
routine repair and replacement of machine parts and
components.
Proactive maintenance -- a
type of condition-based maintenance emphasizing the
routine detection and correction of root cause conditions
that would otherwise lead to failure. Such root causes
as high lubricant contaminant, alignment and balance
are among the most critical.
PSIA -- pounds per square
inch absolute. (PSIG + 14.696)
PSID -- pounds per square
inch differential.
PSIG -- pounds per square
inch gauge (PSIA - 14.696)
Pump -- a device which converts
mechanical force and motion into hydraulic fluid power.
Pumpability -- the low temperature,
low shear stress-shear rate viscosity characteristics
of an oil that permit satisfactory flow to and from
the engine oil pump and subsequent lubrication of moving
components.
Pump, fixed displacement -- a
pump in which the displacement per cycle cannot be varied.
Pump, variable displacement -- a
pump in which the displacement per cycle can be varied.
Rate of shear -- the difference
between the velocities along the parallel faces of a
fluid element divided by the distance between the faces.
Reducer -- a connector having
a smaller line size at one end than the other.
Refraction -- the change
of direction or speed of light as it passes from one
medium to another.
Rerefining -- a process of
reclaiming used lubricant oils and restoring them to
a condition similar to that of virgin stocks by filtration,
clay adsorption or more elaborate methods.
Reservoir -- a container
for storage of liquid in a fluid power system.
Reservoir (sump) filter -- a
filter installed in a reservoir in series with a suction
or return line.
Residual dirt capacity -- the
dirt capacity remaining in a service loaded filter element
after use, but before cleaning, measured under the same
conditions as the dirt capacity of a new filter element.
Return line -- a location
in a line conducting fluid from working device to reservoir.
Return Line Filtration -- filters
located upstream of the reservoir but after fluid has
passed through the system's output components (cylinders,
motors, etc.).
Ring lubrication -- a system
of lubrication in which the lubricant is supplied to
the bearing by an oil ring.
Rings -- circular metallic
elements that ride in the grooves of a piston and provide
compression sealing during combustion. Also used to
spread oil for lubrication.
Ring sticking -- freezing
of a piston ring in its groove in a piston engine or
reciprocating compressor due to heavy deposits in the
piston ring zone.
Roll-off cleanliness -- the
fluid system contamination level at the time of release
from an assembly or overhaul line. Fluid system life
can be shortened significantly by full-load operation
under a high fluid contamination condition for just
a few hours. Contaminant implanted and generated during
the break-in period can devastate critical components
unless removed under controlled operating and high performance
filtering conditions.
Roller bearing -- an antifriction
bearing comprising rolling elements in the form of rollers.
Rust prevention test (turbine oils) -- a test for determining the ability of an oil to aid in preventing
the rusting of ferrous parts in the presence of water.
Sample preparation -- fluid
factors that can enhance the accuracy of the particulate
analysis. Such factors include particle dispersion,
particle settling, and sample dilution.
Saturation level -- the amount
of water that can dissolve in a fluid.
Saybolt Universal Viscosity (SUV) or Saybolt
Universal Seconds, (SUS) -- the time
in seconds required for 60 cubic centimeters of a fluid
to flow through the orifice of the Standard Saybolt
Universal Viscometer at a given temperature under specified
conditions. (ASTM Designation D 88.)
Scuffing -- abnormal engine
wear due to localized welding and fracture. It can be
prevented through the use of antiwear, extreme-pressure
and friction modifier additives.
Scuffing particles -- large
twisted and discolored metallic particles resulting
from adhesive wear due to complete lubricant film breakdown.
Semisolid -- any substance
having the attributes of both a solid and a liquid.
Similar to semiliquid but being more closely related
to a solid than a liquid. More generally, any substance
in which the force required to produce a deformation
depends both on the magnitude and on the rate of the
deformation.
Shear rate -- rate at which
adjacent layers of fluid move with respect to each other,
usually expressed as reciprocal seconds.
Shear stress -- frictional
force overcome in sliding one "layer" of fluid
along another, as in any fluid flow. The shear stress
of a petroleum oil or other Newtonian fluid at a given
temperature varies directly with shear rate (velocity).
The ratio between shear stress and shear rate is constant;
this ratio is termed viscosity of a Newtonian fluid,
the greater the shear stress as a function of rate of
shear. In a non-Newtonian fluid -- such as a grease
or a polymer-containing oil (e.g. multi-grade oil) --
shear stress is not proportional to the rate of shear.
A non-Newtonian fluid may be said to have an apparent
viscosity, a viscosity that holds only for the shear
rate (and temperature) at which the viscosity is determined.
Silt -- contaminant particles
5 µm and less in size.
Silting -- a failure generally
associated with a valve which movements are restricted
due to small particles that have wedged in between critical
clearances (e.g., the spool and bore.)
Single-pass test -- filter
performance tests in which contaminant which passes
through a test filter is not allowed to recirculate
back to the test filter.
Sintered medium -- a metallic
or nonmetallic filter medium processed to cause diffusion
bonds at all contacting points.
Sleeve bearing -- a journal
bearing, usually a full journal bearing.
Sludge -- insoluble material
formed as a result either of deterioration reactions
in an oil or of contamination of an oil, or both.
Solid -- any substance having
a definite shape which it does not readily relinquish.
More generally, any substance in which the force required
to produce a deformation depends upon the magnitude
of the deformation rather than upon the rate of deformation.
Solvency -- ability of a
fluid to dissolve inorganic materials and polymers,
which is a function of aromaticity.
Specific gravity (liquid) -- the
ratio of the weight of a given volume of liquid to the
weight of an equal volume of water.
Specific gravity -- the ratio
of the weight of a given volume of material to the weight
of an equal volume of water.
Spectrographic analysis -- determines
the concentration of elements represented in the entrained
fluid contaminant.
Spectrographic Oil Analysis Program (SOAP)
-- procedures for extracting fluid samples from operating systems and
analyzing them spectrographically for the presence of
key elements.
Spin-on filter -- a throw-away
type bowl and element assembly that mates with a permanently
installed head.
Spindle oil -- a light-bodied
oil used principally for lubricating textile spindles
and for light, high-speed machinery.
Splash lubrication -- a system
of lubrication in which parts of a mechanism dip into
and splash the lubricant onto themselves and/or other
parts of the mechanism.
Static friction -- the force
just sufficient to initiate relative motion between
two bodies under load. The value of the static friction
at the instant relative motion begins is termed break-away
friction.
Stoke (St) -- kinematic measurement
of a fluid's resistance to flow defined by the ratio
of the fluid's dynamic viscosity to its density.
Strainer -- a coarse filter
element (pore size over approximately 40 µm)
Suction filter -- a pump
intake-line filter in which the fluid is below atmospheric
pressure.
Sulfated ash -- the ash content
of fresh, compounded lubricating oil as determined by
ASTM Method D 874. Indicates level of metallic additives
in the oil.
Sulfurized oil -- oil to
which sulfur or sulfur compounds have been added.
Surface fatigue wear -- the
formation of surface or subsurface cracks and fatigue
crack propagation. It results from cyclic loading of
a surface.
Surface filtration -- filtration
which primarily retains contaminant on the influent
surface.
Surface tension -- the contractile
surface force of a liquid by which it tends to assume
a spherical form and to present the least possible surface.
It is expressed in dynes/cm or ergs/cm2.
Surfactant -- surface-active
agent that reduces interfacial tension of a liquid.
A surfactant used in a petroleum oil may increase the
oil's affinity for metals and other materials.
Surge -- a momentary rise
of pressure in a circuit.
Swarf -- the cuttings, and
grinding fines that result from metal working operations.
Switch, pressure -- an electric
switch operated by fluid pressure.
Synthetic lubricant -- a
lubricant produced by chemical synthesis rather than
by extraction or refinement of petroleum to produce
a compound with planned and predictable properties.
Synthetic hydrocarbon -- oil
molecule with superior oxidation quality tailored primarily
out of paraffinic materials.
Thermography -- the use of
infrared thermography whereby temperatures of a wide
variety of targets can be measured remotely and without
contact. This is accomplished by measuring the infrared
energy radiating from the surface of the target and
converting this measurement to an equivalent surface
temperature.
Thermal conductivity -- measure
of the ability of a solid or liquid to transfer heat.
Thermal stability -- ability
of a fuel or lubricant to resist oxidation under high
temperature operating conditions.
Thin film lubrication -- a
condition of lubrication in which the film thickness
of the lubricant is such that the friction between the
surfaces is determined by the properties of the surfaces
as well as by the viscosity of the lubricant.
Thixotropy -- that property
of a lubricating grease which is manifested by a softening
in consistency as a result of shearing followed by a
hardening in consistency starting immediately after
the shearing is stopped.
Three-body abrasion -- a
particulate wear process by which particles are pressed
between two sliding surfaces.
Thrust Bearing -- an axial-load
bearing.
Timken OK Load -- the heaviest
load that a test lubricant will sustain without scoring
the test block in the Timken Test procedures, ASTM Methods
D 2509 (greases) and D 2782 (oils).
Total Acid Number (TAN) -- the
quantity of base, expressed in milligrams of potassium
hydroxide, that is required to neutralize all acidic
constituents present in 1 gram of sample. (ASTM Designation
D 974.)
Total Base Number (TBN) -- the
quantity of acid, expressed in terms of the equivalent
number of milligrams of potassium hydroxide that is
required to neutralize all basic constituents present
in 1 gram of sample. (ASTM Designation D 974.)
Tribology -- the science
and technology of interacting surfaces in relative motion,
including the study of lubrication, friction and wear.
Tribological wear is wear that occurs as a result of
relative motion at the surface.
Turbidity -- the degree of
opacity of a fluid.
Turbulent flow sampler -- a
sampler that contains a flow path in which turbulence
is induced in the main stream by abruptly changing the
direction of the fluid.
Unloading -- the release
of contaminant that was initially captured by the filter
medium.
Vacuum separator -- a separator
that utilizes subatmospheric pressure to remove certain
gases and liquids from another liquid because of their
difference in vapor pressure.
Valve, by-pass -- a valve
whose primary function is to provide an alternate flow
path.
Valve, directional control -- a
valve whose primary function is to direct or prevent
flow through selected passages.
Valve, directional control, servo -- a directional control valve which modulates flow or pressure as a
function of its input signal.
Valve, flow control -- a
valve whose primary function is to control flow rate.
Valve, pressure control, relief -- a pressure control valve whose primary function is to limit system
pressure.
Valve, relief, differential pressure -- a
valve whose primary function is to limit differential
pressure.
Valve -- a device which controls
fluid flow direction, pressure, or flow rate.
Valve lifter -- sometimes
called a "cam follower," a component in engine
designs that use a linkage system between a cam and
the valve it operates. The lifter typically translates
the rotational motion of the cam to a reciprocating
linear motion in the linkage system.
Vapor pressure -- pressure
of a confined vapor in equilibrium with its liquid at
specified temperature thus, a measure of a liquid's
volatility.
Vapor Pressure-Reid (RVP) -- measure
of the pressure of vapor accumulated above a sample
of gasoline or other volatile fuel in a standard bomb
at 100°F (37.8°C). Used to predict the vapor locking
tendencies of the fuel in a vehicle's fuel system. Controlled
by law in some areas to limit air pollution from hydrocarbon
evaporation while dispensing.
Varnish -- when applied to
lubrication, a thin, insoluble, nonwipeable film deposit
occurring on interior parts, resulting from the oxidation
and polymerization of fuels and lubricants. Can cause
sticking and malfunction of close-clearance moving parts.
Similar to, but softer, than lacquer.
Viscometer or Viscosimeter -- an
apparatus for determining the viscosity of a fluid.
Viscosity -- measurement
of a fluid's resistance to flow. The common metric unit
of absolute viscosity is the poise, which is defined
as the force in dynes required to move a surface one
square centimeter in area past a parallel surface at
a speed of one centimeter per second, with the surfaces
separated by a fluid film one centimeter thick. In addition
to kinematic viscosity, there are other methods for
determining viscosity, including Saybolt Universal Viscosity
(SUV), Saybolt Furol viscosity, Engier viscosity, and
Redwood viscosity. Since viscosity varies in inversely
with temperature, its value is meaningless until the
temperature at which it is determined is reported.
Viscosity, absolute -- the
ration of the shearing stress to the shear rate of a
fluid. It is usually expressed in centipoise.
Viscosity, kinematic -- the
absolute viscosity divided by the density of the fluid.
It is usually expressed in centistokes.
Viscosity, SUS -- Saybolt
Universal Seconds (SUS), which is the time in seconds
for 60 milliliters of oil to flow through a standard
orifice at a given temperature. (ASTM Designation D88-56.)
Viscosity grade -- any of
a number of systems which characterize lubricants according
to viscosity for particular applications, such as industrial
oils, gear oils, automotive engine oils, automotive
gear oils, and aircraft piston engine oils.
Viscosity index (VI) -- a
commonly used measure of a fluid's change of viscosity
with temperature. The higher the viscosity index, the
smaller the relative change in viscosity with temperature.
Viscosity index improvers -- additives
that increase the viscosity of the fluid throughout
its useful temperature range. Such additives are polymers
that possess thickening power as a result of their high
molecular weight and are necessary for formulation of
multi-grade engine oils.
Viscosity modifier -- lubricant
additive, usually a high molecular weight polymer, that
reduces the tendency of an oil's viscosity to change
with temperature.
Viscous -- possessing viscosity.
Frequently used to imply high viscosity.
Volatility -- this property
describes the degree and rate at which a liquid will
vaporize under given conditions of temperature and pressure.
When liquid stability changes, this property is often
reduced in value.
Wear -- the attrition or
rubbing away of the surface of a material as a result
of mechanical action.
Wicking -- the vertical absorption
of a liquid into a porous material by capillary forces.
ZDDP -- an antiwear additive
found in many types of hydraulic and lubricating fluids.
Zinc dialkyldithiophosphate. |
