Table of Contents

Preface .................................................................................................. 2
Overview ............................................................................................... 3
Why Analyze Used Lubricants .............................................................. 4
What Are Lubricants? ........................................................................... 5
Functions of a Lubricant? ...................................................................... 6
How Do Lube Oils Fail? ......................................................................... 7
What Does Oil Analysis Measure? ........................................................ 8
Wear Mechanisms ................................................................................ 9
Viscosity .............................................................................................. 10
ICP Spectroscopy ................................................................................. 12
Elements.............................................................................................. 14
Crackle Test ......................................................................................... 15
Karl Fischer Water ............................................................................... 15
Demulsibility ....................................................................................... 17
FT-IR Spectroscopy .............................................................................. 18
RPVOT ................................................................................................. 20
Rust Test .............................................................................................. 20
Foam Test ............................................................................................ 21
Base Number ....................................................................................... 22
Fuel Dilution ....................................................................................... 23
Acid Number ....................................................................................... 23
Particle Count ...................................................................................... 24
Ferrous Wear Concentration .............................................................. 29
Analytical Ferrography........................................................................ 30
Classifying Wear .................................................................................. 31
Varnishing Potential ........................................................................... 36
Ultra Centrifuge .................................................................................. 38
Membrane Patch Colorimetry (MPC) ................................................. 38
RULER .................................................................................................. 39
Filter Debris Analysis .......................................................................... 40
Alarm Levels ........................................................................................ 42
Sampling Procedures .......................................................................... 43
GLOSSARY ........................................................................................... 45

Insight Services 1
Preface

th
In writing the 4 edition of “The Practical Guide To Oil Analysis”,
it occurs to me that Insight Services has increased it’s testing
capacity significantly over the last couple of years. From our
industry leading Filter Debris Analysis to our annual turbine
testing, we can provide any number of testing solutions for your
specific needs. The growth from our original roots has been
exciting and I look forward to more innovations in the future.

We remain true to our initial goal with the book - helping you
understand oil analysis. We have helped many companies
develop and implement successful oil analysis programs. Our
unrelenting drive to provide same day turnaround on all
samples every time is the essence of the Insight Services’
culture.

Michael Barrett

INSIGHT SERVICES

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Overview

The practice of oil analysis has drastically changed from its

original inception in the railroad industry. In today’s exploding
computer and information age, oil analysis has evolved into a
mandatory tool in your reliability-centered maintenance
program.

As a predictive maintenance tool, oil analysis is used to uncover,

isolate and offer solutions for abnormal lubricant and machine
conditions. These abnormalities, if left unchecked, usually result
in extensive, sometimes catastrophic damage causing lost
production, extensive repair costs, and even operator accidents.

The goal of a world-class oil analysis program is to increase the

reliability and availability of your machinery, while minimizing
maintenance costs associated with oil change-outs, labor,
repairs and downtime. Accomplishing your goal takes time,
training and patience. However, the results are dramatic and
the documented savings in cost avoidance are significant!

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Why Analyze Used
Lubricants

Three Aspects of Oil Analysis

LUBRICANT
CONDITION

CONTAMINANTS MACHINE
WEAR

Lubricant Condition. The assessment of the lubricant condition

reveals whether the system fluid is healthy and fit for further
service, or is ready for a change.

Contaminants. Ingressed contaminants from the surrounding

environment in the form of dirt, water and process
contamination are the leading cause of machine degradation
and failure. Increased contamination alerts you to take action in
order to save the oil and avoid unnecessary machine wear.

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Machine Wear. An unhealthy machine generates wear particles
at an exponential rate. The detection and analysis of these
particles assist in making critical maintenance decisions.
Machine failure due to worn out components can be avoided.
Remember, healthy and clean oil lead to the minimization of
machine wear.

What Are Lubricants?

Industrial oils are specially designed fluids composed of
a base oil and a compliment of additives.

The Base Oil performs the following functions:

• Form a fluid film between moving parts in order to

reduce friction and wear.
• Carry away contaminants to the filter.
• Remove heat generated within the machine.

Additives are chemical compounds added to the base oil to

significantly enhance the performance characteristics of the
lubricating oil. Typical enhanced properties include:

• Oxidation Stability.
• Wear Protection.
• Corrosion Inhibition.

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Functions of a Lubricant?
From cooling to cleaning to lubricating, the absolute key
to keeping your equipment running.

LUBRICATE
By introducing a film between moving parts, opposing friction
surfaces are separated and allowed to move freely without any
interlocking of the asperities at the metal surface. By physically
separating the moving parts, friction is greatly reduced. The
result is less wear generated and less energy required to
perform the work.

COOL
Lubricants absorb the heat generated at the friction surface and
carry it away to a reservoir where it is allowed to cool before
returning for service. Oil coolers and heat exchangers are
sometimes used to more efficiently disperse heat. Lubricants
are an excellent dissipator of heat.

CLEAN
Oil picks up solid contaminants and moves them away from the
contact zone. The contaminants can then be removed by
filtration or settling in the reservoir. Many oils have detergent
characteristics to hold tiny dirt and soot particles in suspension
at help prevent sludge and varnish in a system.

PROTECT
Lubricants coat component surfaces providing a barrier against
moisture. The presence of moisture in the air causes oxidation,

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eventually leading to corrosion. Rust occurs when steel surfaces
are attacked by moisture. Corrosion occurs when a metal
surface is attacked by acids, a byproduct of oxidation. Oils can
be fortified with alkaline reserves to counter the corrosive
contaminants.

SEAL
Many lubricants form a viscous seal to keep contaminants out of
a component. Greases form physical barriers to protect against
dirt and water ingress.

TRANSMIT POWER
Hydraulic systems use lubricants to protect sliding, contacting
surfaces and as a source of fluid power. Fluid under pressure
actuates moving parts.

How Do Lube Oils Fail?

Contamination , degradation , or the loss of specific
properties provided by additives.

CONTAMINATION

• External Sources: Dirt, water, and process related

liquids or materials.
• Internal Sources: Machine wear and degradation by-
products

OIL DEGRADATION

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 • Oxidation: What is it? Atmospheric oxygen combines
with hydrocarbon molecules. The hotter the oil and
the greater exposure to air, the faster oxidation
proceeds. The initial by-products of oxidation are
sludges and varnishes. However, further oxidation
converts these by-products into carboxylic acids. These
acids aggressively attack and corrode many machine
component surfaces.

ADDITIVE DEPLETION

• Additives are consumed or chemically changed while

performing their function. The performance
characteristics of the lubricant are altered and the
enhanced properties are wiped out.

What Does Oil Analysis

Measure?
Physical and chemical properties of the oil,
contamination, and mechanical wear.

LUBRICATING OIL PROPERTIES. Uncover contamination or

degradation by trending rates of change in selected lube
properties.

• Fourier Transform Infrared (FT-IR)

Degradation by-products (oxidation, nitration, sulfate).
External contaminants (water, glycol, fuel, soot).

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 • Viscosity
Physical property.
• Karl Fischer Water
Contamination.
• Acid Number (AN)
Degradation.
• Particle Counting
Both contamination and wear debris.

MECHANICAL WEAR. Uncover machine related problems.

• ICP Spectroscopy
Wear metals, contaminant metals, additive metals.
• Ferrous Wear Concentration
Ferrous wear particles.
• Analytical Ferrography
Type and severity of wear particles.

Wear Mechanisms

TYPE CAUSE
Abrasive Wear Hard particles between or embedded in
adjacent moving surfaces.

Adhesive Wear Metal to metal contact due to

overheating or insufficient lubrication.

Fatigue Wear Repeated stress on friction surface

leading to microcracks and spalling.

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Corrosive Wear Water or chemical contamination.

Erosive Wear Particles and high fluid velocity.

Viscosity
Measure of lubricant’s resistance to flow at a specific
temperature.

Operating Principle. Measured

using a viscometer. The sample
is introduced into a “U” shaped
calibrated glass tube, submerged
in a constant temperature bath.
The oil is warmed to a desired
temperature of 40°C or 100°C
and allowed to flow via gravity
down the tube and up the other
side. The number of seconds the oil takes to flow through the
calibrated region is measured. The viscosity in centistokes (cSt)
is the flow time (seconds) multiplied by the tube constant.

Significance. Viscosity is measured at 40°C for industrial

applications and 100°C for engine oil applications. Viscosity for
industrial lubricants is classified using the ISOVG (International
Standard Organization Viscosity Grade) system which is the
average viscosity (cSt) at 40°C. Viscosity for engine oils is
classified according to SAE (Society of Automotive Engineers).
Viscosity is the most important physical property of oil.
Viscosity determination provides a specific number to compare

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to the recommended oil in service. An abnormal viscosity (+
10%) is usually indicative of a problem.

VISCOSITY (centistokes) ASTM D 445

Date Reference 1/11/07 12/7/06 11/2/06 10/19/06

Lab Number 107391 168113 168112 168111 168110

40 cSt 219.3 221 220.9 221.3 220.7

⇑ An increase in viscosity may indicate:

• Increasing suspended solid material such as

wear particles, contamination, or soot.
• Additions of a higher viscosity oil.
• Lubricant oxidation.

⇓ A decrease in viscosity may indicate:

• Contamination from water, fuels, or process

fluid.
• Additions of a lower viscosity oil.
• Additive shear.
•

Advantages. Quickly detects the addition of a wrong oil. Quick

and inexpensive to run. Best measurement of oil serviceability.

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Application. All industrial lubricants.

ICP Spectroscopy
Measures the concentration of wear metals, contaminant
metals and additive metals in a lubricant.

Operating Principle. A diluted oil sample is atomized by inert

gas (argon) to form an aerosol. This is magnetically induced to
form a plasma at a 9000° C. The high temperature causes metal
ions to take on energy and
release new energy in the
form of photons. A spectrum
with different wavelengths is
created for each element.
The instrument quantifies
the amount of energy
emitted and determines the
concentration in parts per
million (ppm) of 20 elements present in the sample.

Significance. The Inductively Coupled Plasma (ICP)

Spectrometer measures and quantifies the elements associated
with wear, contamination, and additives. This information
assists decision makers in determining the oil and machine
condition. The following list outlines the specific elements
detected and possible sources of the element.

Advantages. Very repeatable, proven technology.

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Disadvantages. Can not detect particles greater than 7 microns
in size. Level of additive elements not necessarily indicative of
additive package depletion.

Application. All industrial lubricants.

SPECTROSCOPIC ANALYSIS (ppm) ASTM D 5185

Date Reference 1/11/07 12/7/06 11/2/06

Lab Number 107391 168113 168112 168111

Iron 0 277 142 55

Copper 0 10 6.1 4.3

Lead 0 4.7 0 0

Aluminum 0 0 0 0

Chromium 0 3 0 0

Nickel 0 0 0 0

Silicon 2 105 55 25

Boron 0 3.4 1.6 1.2

Phosphorous 47 56 57 48

Zinc 87 55 35 21

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Elements
Elements Possible Source

Iron (Fe) Shafts, Gears, Housings, Piston Rings,

Cylinder Walls
Copper (Cu) Brass/Bronze Alloys, Bearings,
Bushings, Thrust Washers
Lead (Pb) Bearings, Anti-Wear Gear
Tin (Sn) Bearing Alloys, Bearing Cages, Solder
Aluminum (Al) Pumps, Thrust Washers, Pistons
Chromium (Cr) Roller Bearings, Piston Rings, Cylinder
Walls
Nickel (Ni) Pumps, Gear Platings, Valves
Titanium (Ti) Exotic Alloy
Silver (Ag) Some Bearings
Magnesium (Mg) Detergent Additive, Coolant Additive
Silicon (Si) Dirt, Defoamant Additive
Boron (B) Anti-corrosion in Coolants
Sodium (Na) Detergent Additive, Coolant Additive
Barium (Ba) Rust and Corrosion Inhibitors
Calcium (Ca) Detergent/Dispersant Additive
Phosphorus (P) Anti-wear Additive, EP Gear Additive
Potassium (K) Coolant Additive
Molybdenum (Mo) EP Additive
Zinc (Zn) Anti-wear Additive
Vanadium (V) Turbine Blades

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Crackle Test
Quick screen to determine if a sample contains
moisture.

Operating Principle. A drop of oil is placed on a hotplate that

has been heated to approximately 600° F. The sample drop
bubbles, spits, crackles or pops when moisture is present.
When moisture is detected, a Karl Fischer water test is
performed.

Significance. A crackle test is a good screening test to use to

determine if a sample contains moisture.

Advantages. This is a very low cost test. It is a good way to

determine the need for further moisture analysis.

Disadvantages. The crackle test can only detect moisture

greater than .05% (500ppm). A sample with entrained gas
often results in false positive results.

Applications. All lubricants that are non-water based.

Karl Fischer Water

Quantifies the amount of water in the lubricant.

Operating principle. A reagent is titrated into a measured

amount of sample and reacts with the OH molecules present in
the moisture. This depolarizes an electrode and determines the

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titration endpoint. Results are reported as either % water or
ppm (1% =10,000ppm).

Significance. Water seriously damages the

lubricating properties of oil and promotes
component corrosion. Increased water
concentrations indicate possible
condensation, coolant leaks, or process
leaks around the seals.

KARL FISCHER WATER ( %)

Date Reference 1/11/07 12/7/06 11/2/06 10/19/06

Lab Number 107391 168113 168112 168111 168110

% Water .001 .92 .81 2.604 .024

Advantages. Accurate to .001%. Quantifies both emulsified

and free water.

Disadvantages. Sulfur , acetones and ketones can sometimes

trigger erroneous readings.

Applications. All lubricants, especially effective in systems

sensitive to water.

Forms of water in oil:

• Free water (emulsified or in droplets).
• Dissolved water.

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Water contamination causes:
• Fluid breakdown, such as additive precipitation and oil
oxidation.
• Reduced lubricating film thickness.
• Corrosion.
• Accelerated metal surface fatigue.

Sources of water contamination:

• Heat exchanger leaks.
• Seal leaks.
• Condensation of humid air.
• Inadequately sealed reservoir covers.

Demulsibility
Measures the ability of a lubricant to separate from
water.

Operating Principle. Combine 40 ml of

distilled water with 40 ml of oil in a
graduated cylinder. Place in a constant
temperature bath and stir for 5 minutes.
The amount of oil separation is recorded
at 5 minute intervals over a period of 60
minutes. Failure is considered an
emulsion layer greater than 3ml at the
end of the test

The results are reported as such: [40-40-0

(60)]

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ml ml ml Minutes
oil water emulsions
40 40 0 60

After 60 minutes this sample passed. It contained 40 ml of oil,

40 ml of water and 0 emulsion. This sample separates water and
therefore, has good demulsibility.

Significance. Lubricating oils used in circulating systems should

separate readily from water that may enter the system as a
result of condensation or other means. If the water separates
easily, it will settle to the bottom of the reservoir where it can
be periodically drained.

FT-IR Spectroscopy
Measures the chemical composition of a lubricant.

Operating Principle. Every compound has a unique infrared

signature. Using a Fourier Transform Infrared (FT-IR)
Spectrometer, these key
signature points of a
specific lubricant in the
spectrum are monitored.
These signatures are
usually common
contaminants and
degradation by –products
unique for a particular lubricant.

Significance. Molecular analysis of lubricants and hydraulic

fluids by FT-IR spectroscopy produces direct information on

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molecular species of interest, including additives, fluid
breakdown products and external contamination. Infrared
spectrum of used oil is compared to baseline spectrum (baseline
spectrum chosen from one of five groups depending on oil
type). The differences in IR spectrum are quantified. Levels of
oxidation, nitration and sulfate by-products are reported along
with soot, water, and glycol.

Oil Degradation by chemical change:

• Oxidation. At elevated temperatures, oil exposed to

oxygen from the air will oxidize to form a variety of
compounds. The majority of these are carbonyl
containing compounds e.g. carboxylic acid.
• Nitration. Results from the reaction of oil components
with nitrogen oxides.
• Sulphate. Various oxides of sulfur and water react
together to form acid. Their acid is neutralized by
basic reserve and normally results in formation of
metallic sulfates
• Soot. Measure of the level of partially burned fuel in
oil. Relevant for diesel engines.
• Glycol. Coolant leak

Advantages. Provides information on the overall degradation

of an oil. Assists in optimizing oil change outs.

Disadvantages. Imprecise quantification of water and glycol levels.

Applications. All industrial lubricants.

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RPVOT
Rotating Pressure Vessel Oxidation Test

Significance. Measures the resistance of an oil to oxidation

when subjected to accelerated oxidation in a sealed chamber
filled with pure oxygen under pressure and at elevated
temperatures. This is influenced by the quantity and type of
antioxidants, the presence of natural inhibitors in the base oil,
and the resilience of the base oil to oxidation. As a lubricant
absorbs oxygen, pressure in the sealed chamber drops. The
results of this test are reported as the time (minutes) until the
pressure drops to a predetermined level.

Rust Test
Rust preventing characteristics of oil in the presence of
water.

Operating Principle. A portion of the

oil is placed in a beaker along with
water and a polished steel rod. The
beaker is then immersed in a heated
bath and is stirred for 4 hours. At the
end of the 4 hours, the steel rod is
inspected for the presence of rust /
corrosion.

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Significance. Evaluates the ability of the lubricant to prevent the
corrosion of ferrous parts should water become mixed with the
oil.

Application. Turbines or any other machine where there is a

concern of corrosion with the presence of water.

Foam Test
Measures the foaming tendency of a lubricant.

Operating Principle. Air is forced through a diffuser within a

portion of oil creating foam. After 5 minutes of blowing, the
amount of foam is
recorded. Then,
the sample is
observed for the
clearing of
generated foam.
Then either time of
full dissipation is
recorded or
amount of foam
remaining after 10
minutes.

Significance. The tendency of lubricants to foam can cause

serious issues in systems with high-speed operations. Not only
can foam cause inadequate lubrication but also other problems
such as overflowing reservoirs.

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Base Number
Measures the reserve alkalinity in a lubricant.

Operating Principle. A weighed amount of sample in titration

solvent is titrated with a hydrochloric acid solution to a definite
end point.

Significance. The amount of reserve alkalinity in a lubricant is

critical for certain oils. Often an oil is fortified with alkaline
additives to combat acid formation. The TBN is at its highest as a
new oil and decreases with service.

BASE NUMBER (mg KOH / g)

Date Reference 1/11/07 12/7/06 11/2/06 10/19/06

Lab 107391 168113 168112 168111 168110

Number

Base # 8.5 6.0 5.8 7.1 7.5

Applications. Diesel engines.

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Fuel Dilution
Measures amount of fuel (%) present in an engine oil.

Operating Principle. The instrument samples the headspace

above a sample for fuel vapors. A pump inside of the test
equipment draws the vapors across a sensor where absorbed
hydrocarbons are measured in percent fuel present.

Significance. Fuel dilution in engine oils is measured by this

process and returns a value in percent fuel dilution. Excessive
fuel dilution can cause a drastic drop in viscosity which may lead
to increased wear.

Application. Diesel and Gasoline Engines.

Acid Number
Measures the acidity of a lubricant.

Operating Principle. A weighed amount of sample in titration

solvent is titrated with a potassium hydroxide solution to a
definite end point.

Description. Organic acids, a by-product of oil oxidation,

degrade oil properties and lead to corrosion of the internal
components. The AN is lowest as a virgin oil and can gradually
increase with use. High acid levels are typically caused by oil
oxidation.

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 ACID NUMBER (mg KOH / g)

Date Reference 1/11/07 12/7/06 11/2/06 10/19/06

Lab Number 107391 168113 168112 168111 168110

1.6 1.95 1.98 1.67 1.7

Acid #

Advantages. A sudden rise in acid number is an alarm for an oil

change.

Applications. All lubricating systems where extended drain

intervals are considered. Limited applications for combustion
engines.

Particle Count
Measures the size and quantity of particles in a lubricant.

Operating Principle. Light Blockage Principle. A known volume

of oil (5ml) is injected through a sampling cell. On one side of
the cell is a beam of laser light and on the other side is a
detector. As particles pass through the cell, they block the
beam and cast shadows on the detector The drop in light
intensity received by the detector is proportional to the size of
particle blocking the light beam. Both the number and size of
particles are measured.

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Operating Principle. Fluid Flow Decay Principle. Oil is passed
through a screen of known
mesh size (10 micron) and
the time taken to plug the
screen is determined. The
instrument then calculates
the distribution in the
other predetermined size
ranges by extrapolation.

Significance. Optical particle counters use the light blockage

method and are particularly effective in clean systems such as
turbines and hydraulics. However, this method yields
inaccurate results in the presence of water or air bubbles. Pore
blockage particle counters are based on the fluid flow decay
principle. Their data is not effected by air bubbles or water.

PARTICLE COUNT (per ml) ISO 4406:99

Date Reference 1/11/07 12/7/06 11/2/06 10/19/06

Lab Number 107391 168113 168112 168111 168110

15/14/11 21/19/17 19/17/15 18/17/13 17/16/13

ISO CODE

>4 311 10156 2518 1456 899

>6 114 2695 789 654 401

> 14 12 1256 198 78 52

> 50 0 25 5 2 1

> 100 0 12 2 0 0

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Advantages. Excellent for “clean” systems (turbines, hydraulics
etc.). Limits provided by equipment manufactures determine
filter efficiency.

Disadvantages. Abnormal wear can be masked on systems with

routinely high levels of particulate matter. Does not determine
what TYPE of debris is in sample.

Application. Use whenever equipment manufacturer provides

recommended lubricant cleanliness levels. Turbines, Boiler Feed
Pumps, EHC Systems, Hydraulics, Servo Valves. Any
system where oil cleanliness is directly related to longer lubricant
life, decreased equipment wear or improved equipment
performance.

Sources of Contamination

Built in contaminants. This is residual contamination remaining

in a system during construction or assembly.

External ingression. This is contamination which enters the

systems from outside. Possible sources include: during an oil fill,
leaving breathers off, leaving covers off the reservoir, or faulty
seals.

Internally generated. This is wear debris normally caused by

the two sources above. If you can control built- in and ingressed
contamination, wear debris will be generated at significantly
lower levels.

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 Target Cleanliness

Pressure Range

>2500 1500-2500 <1500

Component
Servo Valve 14/12/10 15/13/11 16/14/12
Proportional Valve 15/13/11 16/14/12 17/15/12
Fixed Piston Pump 17/15/12 17/16/13 18/16/14
Vane Pump 17/16/13 18/16/14 19/17/14
Pressure Control Valve 17/16/13 18/16/14 19/17/14
Gear Pump 17/16/13 18/16/14 19/17/14
Roller Bearing System 16/14/12
Journal Bearings 18/16/14

Insight Cleanliness Code

The Insight cleanliness code references a three-digit code that

represents the cumulative number of particles greater than 4, 6
and 14 microns in the fluid. The number of particles at each size
range is cross-referenced to the following table to locate the ISO
contamination code. The code is written as three numbers with
a slash, “ / “ , between them. For example: 21/19/15. The first
number represents the code number at 4 micron, the second
number the code number at 6 micron, and the third number the
code number at 14 micron.

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 Making Sense Out of ISO Particle Counts

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Ferrous Wear
Concentration
Measures the amount of ferrous wear in a lubricant.

Operating Principle. A wear particle analyzer quantifies the

amount of ferrous material present in a sample of fluid. A
measured amount of sample is inserted into the analyzer and
amount of ferrous material is determined by change in magnetic
flux. This
change is then
converted into
ferrous
concentration
in parts per
million. Instead
of using a light
sensor to
measure particles and report a unitless number, this instrument
measures concentration and reports the results in parts per
million. Using this method, there are no interferences with non-
ferrous particles.

Significance. This test gives a direct measure of the amount of

ferrous wear metals present in a sample. Trending of ferrous
concentration reveals changes in the wear mode of the system.

Advantages. Excellent trending device for “dirty” systems such

as large splash lubricated gearboxes. No particle size limitation.

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Disadvantages. Does not detect non-ferrous particles.

Application. Gearboxes, Anti-Friction bearings.

Analytical Ferrography
Allows analyst to visually examine wear particles present in a
sample.

Operating Principle. To create a ferrogram, a sample of oil is

passed over a glass slide. The
slide rests on a magnetic plate
that attracts ferrous wear
particles in the oil onto the
surface of the slide. The
ferrous wear particles line up
in rows with the largest
particles forming rows at the
top of the ferrogram. Non-
ferrous particles are easily
detected because they deposit randomly across the slide.

Significance. A trained analyst visually determines the type and

severity of wear deposited onto the substrate by using a high
magnification microscope. The particles are readily identified
and classified according to size, shape, and metallurgy.

Advantages. Best method for determining severity and type of

wear present. There are no particle size or metallurgy
limitations. Wear can be documented by digital photography.

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Disadvantages. Subjective results dependent upon the Analyst.
The test is time consuming, labor intensive, and, therefore,
expensive.

Application. Best used when other test methods indicate

possible problems.

Classifying Wear
Rubbing Wear

Description. Ferrous
particles, less than 30 microns
in size. Some Sources:
Rubbing wear is typically
found in both reciprocating
and non-reciprocating units.

Comments. On a ferrogram
the particles tend to align in chains. Normal ferrous wear can be
categorized as low alloy, cast iron and high alloy steel.

Severe Wear

Description. Metallic
particles greater than 30
microns. Fatigue or
component overload that
cause larger pieces of wear to
detach creates severe wear.

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Comments. Severe wear is a definite sign of abnormal running
conditions.

Sliding Wear

Description. Metallic particles, both normal and severe, with

sliding striations along one or more surfaces. Sliding wear can be
created when two parts of a
machine scrape together.

Comments. Sliding striations

are often a good clue as to
what part of a machine is
causing wear.

Laminar

Description. Thin, smooth particles which appear to have been

rolled flat. Roller bearings, areas where high-pressure angled or
lateral contact occurs.

Comments. Wear created by

extraneous particle if the
laminar has small holes or
indents.

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Cutting Wear

Description. Shaved metal particles that look like wood

shavings from a lathe. Seen in
sleeve bearings and shaft
couples. Abrasives embedded
in soft bearing or burrs on
hardened metals create these
wear particles.

Comments. Worm drives have

a tendency to create this type
of particle. When seen it indicates abnormal wear.

Dark Metal Oxide Wear

Description. Grey to black chunks with a semi-metallic

appearance and mottled edges. Some Sources: Breakdown of
boundary film, excessive operating temperatures, lubricant
oxidation.

Comments. The darker the

color, the more severe the
oxidation of the particle.

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Sphere

Description. A relatively
smooth spherical particle.
Spheres are created in bearing
fatigue cracks, typically roller
bearings.

Comments. Spheres are often

precursors of bearing spalls.
A large increase in quantity is
indicative of imminent spalling.

Non-Ferrous Metal Wear

Description. Any metallic particle that is not ferrous. Most

common include aluminum, copper alloy, chrome, and babbitt.
Non-ferrous wear can be created by the machines or as additive
packages in the lubricant.

Comments. Non-ferrous
metallic wear can be across the
entire length of a ferrogram.
These particles will not be
aligned with the ferrous wear
chains.

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Contaminants

Description. Dirt, sand and

other silica particulate.
Contaminants can enter into a
system by a variety of ways:
poor seals, incorrectly installed
breather, during oil change, etc.

Comments. Some can appear

like crystals. Contaminants are easily identified by using only
the transmitted light source on the microscope.

Fiber

Description. Fibers are thread like material made of asbestos,

paper, glass or a synthetic material. Most common source is
filter material. Could be from machine housing, cleaning rages,
or air contaminants.

Comments. A small amount of

fibrous material in oil is common.

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Red Oxide

Description. Iron oxides or

rust. It appears as orange/red
in color. Red oxides are
produced when moisture
enters into a system. Water
does not have to be present
when red oxides are seen, as
they are often difficult to filter
out of oil.

Comments. Red oxides are not necessarily magnetic like ferrous

wear. Alpha hematite is paramagnetic and will be found on all
regions of a ferrogram.

Varnishing Potential
Detect the onset of varnishing problems in turbines and
hydraulics.

Varnish is formed when degradation by-products come out of

solution and form soft contaminants, which can agglomerate
and form varnish deposits. Varnish is detrimental to the
performance of rotating equipment, particularly gas turbines.
Several condition monitoring tests have been developed which
can be used to gauge the varnishing potential of a lubricant.

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 EXAMPLE VARNISHING POTENTIAL
ANALYSIS REPORT

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Ultra Centrifuge
Operating Principle. As an oil sample is
spun at 17,000 rpm in the ultra centrifuge
the soft contaminant oxidation by-
products which have a higher molecular
weight than the oil will be forced to the
bottom of the centrifuge tube.

Significance. The amount of deposited

contaminants can be visually compared
to a scale to quantify the level of
contaminants present in the oil.

Membrane Patch
Colorimetry (MPC)
Operating Principle. Insoluble deposits
are extracted from the sample using a
membrane patch. The color of the patch
is analyzed using a spectrophotometer.
Results are reported as a deltaE value in
the CIE LAB scale.

Significance. The delta E value can be

trended and used to monitor oil
condition with regard to varnish
potential.

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RULER
Operating Principle. Antioxidants are removed from the oil by
mixing sample with a solvent.
The dissolved antioxidants are
then measured using linear
sweep voltammetry.

Significance. By comparing
the levels of antioxidants in
the used oil sample to the
levels present in a virgin
reference sample of the same
lubricant the remaining useful life of the used oil can be
estimated.

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Filter Debris Analysis
Operating Principle. The
FDA instrument is a self-
contained unit which
employs an automated
method for filter washing to
extract all debris from the
filter with high repeatability
and reproducibility. A used
filter is placed in the system
wash chamber and all debris is removed from the filter using a
combination of fluid and pressurized air. The wash fluid carrying
the filter debris passes through an on line sensor which
quantifies and sizes the amount of ferrous debris. The fluid then
runs through a filter patch where the sample of debris is
captured for further metallurgical analysis by X-Ray
Flourescence (XRF). XRF analysis provides the percentage
elemental composition of the sample which can be correlated to
the wear debris of interest.

Significance. In traditional oil analysis, the only particles

available for analysis are those circulating in the oil or
immediately released in the oil prior to sampling. Given the fine
filtration used in rotating equipment today to produce longer
life cycles, 95% of the wear debris which could provide useful
insight into machinery condition is caught in the filter and never
end up in an oil sample. It typically is discarded with the filter.
Increasingly, fine filtration is making conventional monitoring
techniques less effective at providing reliable indication of
machinery component wear. FDA captures this lost information
and identifies the specific components that are wearing,

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providing improved diagnostic and prognostic information
about impending failures.

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Alarm Levels

The alarm level is the difference in world class programs .

In assessing machine condition, it is essential not only to look at

the machine’s current and past data, but also compare that
particular machine with the “family” that the machine is a
member. Families can be made up of machine types,
manufacturers, models and sump capacities depending on the
level of information provided by the user. Statistics are
calculated by looking into the database and extracting previous
test results of “family” data. Family alarming produces tight
limits which provide great value to the oil analysis user.

Another alarming method is to use customer specific limits.

When a customer has previous knowledge of machine fault
levels it is beneficial to provide these hard limits to the lab. They
can be utilized at either the machine or customer level to trigger
appropriate alarms.

If there is not enough information identifying a machine but

there is historical information for the specific sampling point,
alarms can be set by using linear regression.

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Sampling Procedures

Goal: Obtain a sample in a manner that is easily repeatable

and which effectively represents the actual condition of the oil
in the machine. Good sampling ensures consistency and
reliability of data and instills confidence in the decisions made
with your reports.

When to Sample

While equipment is at full operating

temperatures

During operation if possible

Directly after shut down

Where to Sample

Should be good representation of oil in system

Location/Method must be consistent

Never on a “dead leg”

Safely and readily accessible while equipment is running

Should lend itself to a “clean sample”

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Sampling Methods

Non-Pressurized Valves. Install valves upstream of any filter in

order to capture wear particles generated by the machine.
Make sure the valve is clean and adequately flushed.

Pressurized Valves

Use a vacuum pump with appropriate tubing. Make sure to use

new tubing for each sample in order to avoid cross
contamination. Cut the
tubing to the same length
each time you sample. Try
to avoid scraping the tubing
along the sides or bottom of
the tank or reservoir.

Ball Valves

The least desired method

of sample acquisition.
Make sure you drain plenty of oil
before you collect your sample. The
sludge, particles, and water that settle to the bottom of a tank
or reservoir provide poor results.

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GLOSSARY
AF = Analytical ferrography. Powerful diagnostic procedure to
detect large wear particles, i.e. up to 100 microns. Provides a
qualitative assessment of wear generation through microscopic
examination of debris suspended in representative sample of
used oil.

Abrasive particles = Crystalline particles or silica which have

contaminated the oil and when accompanied by cutting wear
particles cause abnormal wear.

Acid number = AN: mg of KOH required to neutralize basic

buffer in oil using the procedure ASTM 974. A reduction
indicates loss of basic reserve indicating possibility of corrosive
wear in diesel engine.

Aluminum alloy = White particles which indicate wear of

aluminum component such as a casing wall.

Babbitt = Particles observed during analytical ferrography which

indicate wear of babbitted bearing.

Cast Iron = Ferrous wear particles observed during analytical

ferrography which can originate from outside of case hardened
gear tooth and is a common material used in machine housings.

Contaminants = Non-metallic particles observed during

analytical ferrography which are being introduced into lube
reservoir. If abrasive particles, increased cutting wear can be
expected.

Copper alloy = Yellow particles indicating wear of copper alloy

component such as an oil ring, bushing, etc.

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Corrosive wear = Dark sub-micron particles observed
microscopically during ferrographic analysis. Caused by acid
attack of metals surfaces when oil is degraded.

cSt = Centistokes (units of viscosity) measured at either 40° C or

100° C.

Cutting wear = Long spiral or crescent shaped particles,

resembling machining swarf. Can be due to abrasives or
misalignment.

Dark Metallo = Oxidized ferrous particles which are very old or

have been recently produced by conditions of inadequate
lubrication.

Density = Mass of oil per unit volume.

Flash C = Flash point = the temperature at which the oil will

produce sufficient volatile vapors to ignite when exposed to test
flame. (ASTM D-92)

Fibers = Natural or synthetic observed by ferrographic analysis

sometimes indicating contamination or filter deterioration.

Friction Polymers = Polymerization of the oil usually due to high

stress. Not generally harmful, expect when it significantly affects
viscosity or blocks fine filters.

FTIR = Fourier Transform Infrared Spectroscopy. A very

effective test for providing levels of soot, sulfates, oxidation,
nitrates, glycol, fuel, and water contaminants.

% Fuel = Calculated using an instrument called a Fuel Sniffer.

Glycol = An approximate percentage measurement of glycol

contamination in oil. Glycol is found in engine coolant.

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High Alloy Steel = Ferrous metal particle observed in analytical
ferrography which is commonly found in shaft material.

ISO 4406:99 = Standard mainly use for hydraulic systems. The

three number code uses an logarithmic scale to classify the
cleanliness of the oil based on the number of particles greater
than 4, 6 and 14 microns.

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 (R) and the
three previous samples are shown.

Insolubles = Particles of carbon or agglomerates of carbon and

other material. Indicates deposition or dispersant dropout in an
engine. Not serious in compressor or gearbox unless there has
been a rapid increase in these particles.

Lab No = Sequential number given to each sample received in

laboratory.

Laminar Particles = Particles generated in rolling element

bearings which have been flattened out by a rolling contact.

Low Alloy Steel = Ferrous particle observed during analytical

ferrography which can originate from anti-friction bearings
(52100 bearing steel) or inside of case hardened gear tooth.

Lubricant condition = Expert system conclusion based on

whether certain limits were exceeded in the oil analysis results.

Machine condition = Expert system conclusion based on

whether certain limits were exceeded in the oil analysis results.

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Machine name = Name of machine which is unique to that unit.
For example, NE gearbox on #4 crane.

Machine type = For example, Internal combustion engine, gas

turbine, centrifugal compressor, etc.

Nitrate = An indicator of oil degradation in gasoline and natural

gas engines.

Oxidation = A trend indicator of oil degradation.

Percent large = WPC results indicating the total weight in

micrograms of large ferrous particles found in 1 ml of oil as a
percentage of total weight of large and small particles.

Physical analysis = Includes common tests for physical and

chemical properties. For example, viscosity, TAN, etc..

Product = The amount of contamination of the oil by

degradation products or external source.

Received = Date and time sample was received.

Recommendations = Maintenance actions indicated.

Red Oxides = Ferrous oxide particles (red) observed by

ferrography where a severe moisture problem is present.

Sample reference = General information on the current and

past samples from the same machine. Indicates time on oil,
time since overhaul, sample date, etc.

Sample date = The date that the oil is sampled as indicated on

the sample bottle by customer.

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Severe sliding = Large ferrous particles which are produced by
sliding contacts. Trend is important to determine whether
abnormal wear is taking place.

SP = Spectroscopy by atomic emission (ICP). The measurement

of small (less than 7 microns) and dissolved metal particles in oil.

Spheres = Small (2-10 micron) ferrous spheres observed during

analytical ferrography which can be indicative of abnormal
rolling wear. Trend is important.

Sulfate = An indicator of oil degradation in diesel engines.

Time on oil = Service time on the oil. Either indicated by the

customer on the sample bottle or estimated by us based on
time elapsed since last sample and average operating hours per
week.

Time since overhaul = Service time of the machine. Either

indicated by the customer on the sample bottle or estimated by
us based on time elapsed since last sample and average
operating hours per week.

Type of machine = Reciprocating engine, gas turbine, centrifugal

compressor, etc..

Viscosity = Measure of oil's resistance to flow at 40 C or 100 C.

All tests are normally done at 40° C, except for engine oils.

Water Kf = Water measurement using Karl Fischer titration.

% Water = Water content expressed in percentage. (0.1% =

1000ppm)

White Non-Ferrous Metallic Particles = observed in Analytical

Ferrography which do not respond to heat treatment. These

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particles are usually aluminum but can also be tin, chrome,
silver and other more exotic metals.

WPC = Wear Particle Concentration. A quantitative ferrous

measurement of ferrous material in oil.

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