fuels midterm Flashcards
The primary purpose of a ______ is to reduce friction between moving parts.
lubricant
In theory, ______ is based on the actual separation of the surfaces so that no metal-to-metal contact occurs.
fluid lubrication
As long as the ________remains unbroken, metallic friction is replaced by the internal fluid friction of the lubricant.
oil film
Under ideal conditions, friction and wear are held to a ________.
minimum
___ is generally pumped throughout the engine to all areas that require lubrication.
Oil
is created when a roller or sphere
rolls over another surface, such as with ball or roller bearings,
Rolling friction
also referred to as antifriction
bearings
Rolling friction
TYPES OF FRICTION
wiping friction, rolling friction
occurs between gear teeth
wiping friction
pressure can vary widely and loads applied to the gears can be extreme, so the lubricant must be able to withstand the loads.
wiping friction
acts as a cushion between metal parts.
oil film
In reciprocating engines, these components are
especially dependent on the oil for _______.
cooling
also aids in forming a seal between the piston and the cylinder wall to prevent leakage of the gases from the combustion chamber.
oil
can account for up to 50 percent of
the total engine cooling
oil cooling
clean the engine by reducing abrasive wear
oils
an additive that holds the
particles in suspension and allows the filter to trap them as the oil passes through the filter.
dispersant, an additive,
prevents corrosion on the interior of the engine by leaving a coating of oil on the parts
when the engine is shut down.
oil
Classifications lubricants according to physical state
LUBRICATING OILS
MINERAL OILS
SYNTHETIC OILS
ANIMAL AND VEGETABLE OIL
MINERAL OR PETROLEUM OIL
BLENDED OILS
sometimes simply called lubricant/lube, is a class of oils used to reduce the friction, heat, and wear between mechanical
components that are in contact with each other.
Lubricating oil,
used in motorized vehicles,
where it is known specifically as motor oil and
transmission fluid.
Lubricating oil
are lubricating oils refined from
naturally occurring crude oil
Mineral oils
currently the most
commonly used type because of the low cost of
extracting the oils from crude oil.
MINERAL OILS
can be manufactured
to have a varying viscosity, therefore making
them useful in a wide range of applications.
MINERAL OILS
are lubricating oils that are
manufactured.
SYNTHETIC OILS
used as a substitute for
petroleum-refined oils when operating in extreme
temperature.
SYNTHETIC OILS
Aircraft jet engines, for example, require the use
of ________, whereas aircraft piston engines
do not.
synthetic oils
GOOD LUBRICATING OIL MUST
POSSES
A low pressure ( high boiling point)
Adequate viscosity for particular service condition
Low freezing point
High oxidation resistant
Heat stability
Non – corrosive properties
Stability to decomposition at the operating temperature
were the most commonly used lubricants
They possess good
oiliness.
oil of vegetable and animal origins
can be used as an alternative fuel in
diesel engines and heating oil burners.
vegetable oil
When vegetable oil is used directly as a fuel, in
either modified or unmodified equipment, it is referred to as
straight vegetable oil (svo) or pure
plant oil (ppo)
can also be blended with
conventional diesel or processed into biodiesel or bioliquids for use under a wider range of conditions
Straight vegetable oil
they are used as a blending agent with other lubricating oil like mineral oils to produce desired effect in
animal and vegetable oil
familiarize
ANIMAL AND VEGETABLE OIL
a) Costly
b) Undergo oxidation easy forming
gummy and acidic products and get
thickened on coming in contact with air.
c) Have some tendency to hydrolyze,
when allowed to remain contact with
moist air or aqueous medium.
ANIMAL AND VEGETABLE OIL
a) Costly
b) Undergo oxidation easy forming
gummy and acidic products and get
thickened on coming in contact with air.
c) Have some tendency to hydrolyze,
when allowed to remain contact with
moist air or aqueous medium.
a liquid by-product of refining crude oil to make gasoline and other petroleum
products.
mineral oil
a transparent,
colorless oil, composed mainly of
alkanes and cycloalkanes, related to
petroleum jelly.
MINERAL OR PETROLEUM OIL
mineral or petroleum oil the most widely used lubricant, because they are:
Cheap
Available in
abundance
Quite stable under
service conditions.
give desired lubricating properties,
required for particular machinery.
blended oils
a) OILINESS-CARRIERS:
b) EXTREME-PRESSURE
ADDITIVES:
c) POUR-POINT:
d) ANTIOXIDANTS OR
INHIBITORS
e) CORROSION PREVENTERS
f) DEPOSIT INHIBITORS:
BLENDED OILS
BLENDED OILS
a) OILINESS-CARRIERS:
b) EXTREME-PRESSURE
ADDITIVES:
c) POUR-POINT:
d) ANTIOXIDANTS OR
INHIBITORS
e) CORROSION PREVENTERS
f) DEPOSIT INHIBITORS:
have higher shear or frictional resistance than oils and, therefore, can support much heavier loads at lower speeds. They also do not require as much attention unlike the lubricating liquids. But have a tendency to separate into oils and soaps.
greases or semi solid
Grease are used:
In situations where oil cannot remain in place, due to high load, low speed,
intermittent operation etc.
In bearing and gears that work at high temperatures
In situations where bearing needs to be sealed against entry of dust, dirt, grit or
moisture, because greases are less liable to contamination.
Dripping or spurting of oil is undesirable,
are materials that,
despite being in the solid phase, are
able to reduce friction between two
surfaces sliding against each other
without the need for a liquid oil
medium.
SOLID LUBRICANTS
The four most commonly used solid lubricants are:
Graphite
Molybdenum disulfide
Hexagonal boron
nitride
Tungsten disulfide
The two main dry lubricants are _______ and _______. They
offer lubrication at temperatures higher than liquid and oil-based lubricants operate. Dry lubricants are often used in applications such as locks or dry lubricated bearings.
graphite and molybdenum disulfide
Solid lubricants are useful for conditions when conventional lubricants are inadequate, such as:
Reciprocating motion:
Ceramics:
High temperature:
Extreme contact pressures:
a lubricant consisting of
chemical compounds that are
artificially made.
synthetic oil
Modern synthetic lubricants possess, in general, the following distinguishing characteristics:
non-inflammable
high flash points
high thermal stability at high operating temperatures
high viscosity-index
chemical stability
FUNCTIONS OF LUBRICANT
Lubricant vs. anti-tack coating
Keep moving parts apart
Reduce friction
Transfer heat
Carry away contaminants and debris
Transmit power
Protect against wear
Prevent corrosion
Lubricant vs. anti-tack coating
Keep moving parts apart
Reduce friction
Transfer heat
Carry away contaminants and debris
Transmit power
Protect against wear
Prevent corrosion
FUNCTIONS OF LUBRICANT
are compounds that prevent crystallization
of waxes.
Pour point depressants
ADDITIVES
Pour point depressants
Anti-foaming agents
Viscosity index improvers (VIIs)
Antioxidants
Detergents
Corrosion inhibitors (rust inhibitors)
Anti-wear additives
Extreme pressure (anti-scuffing)
additives
Friction modifiers
are typically silicone compounds which
increase surface tension in order to
discourage foam formation.
Anti-foaming agents
are compounds that allow lubricants to
remain viscous at higher temperatures.
Viscosity index improvers (VIIs)
suppress the rate of oxidative degradation
of the hydrocarbon molecules within the
lubricant.
Antioxidants
ensure the cleanliness of engine components by preventing the formation of deposits on
contact surfaces at high temperatures.
Detergents
are usually alkaline materials, such as alkyl sulfonate salts, that absorb acids that would corrode metal parts.
Corrosion inhibitors (rust inhibitors)
form protective ‘tribofilms’ on metal
parts, suppressing wear.
Anti-wear additives
form protective films on
sliding metal parts.
Extreme pressure (anti-scuffing)
additives
reduce friction and wear, particularly in the
boundary lubrication regime where
surfaces come into direct contact.
Friction modifiers
Lubricants must have the following main characteristics:
Keep surfaces separate under all loads, temperatures and speeds, thus minimizing
friction and wear.
Act as a cooling fluid removing the heat produced by friction or from external
sources
Remain adequately stable in order to guarantee constant behavior over the forecasted
useful life.
Protect surfaces from the attack of aggressive products formed during operation.
Show cleaning capability and dirt holding capacity in order to remove residue and
debris that may be form during operation.
Keep surfaces separate under all loads, temperatures and speeds, thus minimizing
friction and wear.
Act as a cooling fluid removing the heat produced by friction or from external
sources
Remain adequately stable in order to guarantee constant behavior over the forecasted
useful life.
Protect surfaces from the attack of aggressive products formed during operation.
Show cleaning capability and dirt holding capacity in order to remove residue and
debris that may be form during operation.
Lubricants must have the following main characteristics:
The main properties of lubricants, which are usually indicated in the technical
characteristics of the product, are:
Viscosity
Viscosity index
Pour point
Flash point
describes the flow behavior of a fluid.
viscosity
measurement of viscosity
centistokes (cSt)
viscosity of lubricating oils diminishes as temperature ____ and consequently is measured at a given temperature
rises
when oil is heated its viscosity is _____ , this _____ its load carrying capacity.
reduced, reduces
When temperature______, the lubricant
becomes thinner and the viscosity becomes
lower.
Inversely as the temperature ______, the
lubricant thickens and ______ increases,
making it more difficult to pour or pump.
increases, decreases, viscosity
is a measurement of oil’s
viscosity change due to temperature.
Viscosity Index (VI)
The higher the VI the less it will thicken when
cold, and the less it will thin out when heated.
viscosity
familiarize
What causes viscosity to increase or
decrease increases may be caused but not
limited to oxidation, polymerization,
carbon build-up (Soot), contaminants,
anti-freeze, water ingress and/ or the
addition of a wrong oil type.
Decreases in viscosity could indicate fuel
dilution, sheer down of the VI, thermal
cracking, over extended oil drain periods
and again the addition of a wrong oil type.
familiarize
What causes viscosity to increase or
decrease increases may be caused but not
limited to oxidation, polymerization,
carbon build-up (Soot), contaminants,
anti-freeze, water ingress and/ or the
addition of a wrong oil type.
Decreases in viscosity could indicate fuel
dilution, sheer down of the VI, thermal
cracking, over extended oil drain periods
and again the addition of a wrong oil type.
The_______ of a crude oil, or a petroleum fraction, is the lowest temperature at which the oil will
pour or flow when it is cooled, without stirring, under standard cooling conditions.
represents the lowest temperature at which oil is capable of flowing under gravity
pour point
familiarize
The pour point of crude oils relates to their
paraffin content: the higher the paraffin content,
the higher the pour point.
To improve (reduce) the pour point of these oils,
pour point depressants (PPDs) are added.
familiarize
The pour point of crude oils relates to their
paraffin content: the higher the paraffin content,
the higher the pour point.
To improve (reduce) the pour point of these oils,
pour point depressants (PPDs) are added.
is the minimum temperature at
which an oil-vapor-air-mixture becomes
inflammable.
It is determined by progressively heating the
oil-vapor-air-mixture in a standard laboratory
receptacle until the mixture ignites.
flash point
is sometimes confused with the
autoignition temperature, the temperature that
causes spontaneous ignition.
flash point
is the lowest temperature at which
the vapors keep burning after the ignition source
is removed.
fire point
is a comparison of the weight of
the substance to the weight of an equal volume of
distilled water at a specified temperature.
specific gravity
is often considered to be the life
blood of an engine.
Without it, the friction and wear produced
between moving parts would cause an engine to
wear at a very rapid rate.
lubricating oil
FUNCTIONS OF LUBRICATING OIL
REDUCE FRICTION
ABSORBS HEAT
SEALS
CUSHIONS
CLEANS
PROTECTS AGAINST CORROSION
CHEMICAL PROPERTIES OF
LUBRICATING OILS
Ease of starting rapidity of warming up
Low Carbon Forming Tendency
Carbon residue test methods
High Oxidation Stability
Wear Reduction
Abrasive wear
Corrosive wear
Adhesive wear
Detergency and Dispersancy
Seal compatibility
