Clean Oil Keeps Equipment Running Right
Counting the tiny particles in an oil sample identifies harmful contaminants that shorten component life. It can also pinpoint larger particles that signal imminent equipment failure. Our comprehensive oil analysis program finds these particles through a combination of tests that includes Particle Count.
Fighting an Unseen Enemy
Even particles far too small to see can cause damage. In fact, oil that looks clean may contain particles that cause abrasive wear. Particle contamination:
- Accelerates component wear
- Reduces system efficiency
- Diminishes equipment performance
Learn About ISO Cleanliness Codes
The International Standards Organization (ISO) has developed a code system for convenience in discussing the cleanliness level of a fluid. The system reports on particles at two important size categories (5 micron and 15 micron). You may wish to learn more about this system of reporting oil cleanliness to better manage the life of your hydraulic, transmission, and other drive train components. If you are interested, ask your MacAllister/Caterpillar parts representative for Form No. PEJT5O25 Reporting Particle Count by ISO Code.
Going Beyond Wear Rate Analysis
Particle Count, which is used for hydraulic, transmission, and other drive train system oil samples, is one of two tests in the MacAllister/Caterpillar fluid analysis program that look at particles. The other is Wear Rate Analysis, which uses spectrometry to identify metal particles up to 10 microns in size. Unlike Wear Rate Analysis, Particle Count detects metallic and non-metallic particles from 2 to 100 microns. However, Particle Count only reports the size and number of particles, not their composition.
Particle Count is the most efficient way to identify non-metallic particles in oil. These may include silicon from dirt or synthetic friction materials that signal deterioration in transmissions, steering clutches and brakes. Gasket, seal, filter and hose material can also be detected.
Another benefit of Particle Count is its ability to detect particles larger than 10 microns that cannot be seen by Wear Rate Analysis or any other oil analysis test. These larger particles are a sign of imminent failure if the problem is not corrected.
Particle Count is only used for non-engine oil samples because engine oil contains soot that cannot be distinguished from metal particles or debris.
A Partnership of Tests Identifying Trends
Particle Count works with Wear Rate Analysis to give you a more accurate picture of what’s going on in your machine. Wear Rate Analysis may indicate a sharp rise in the concentration of a certain wear metal. This concentration may then level off, indicating normal wear. But Wear Rate Analysis can only detect particles up to about 10 microns. A Particle Count run on the same sample could show a sharp rise in particles over 15 microns. The two trends together may show a failure in progress, or an intrusion of external contaminants.
The Two Methods for Reading Particles
The ISO Code rating system is a standard way of measuring oil cleanliness and is used to express the Particle Count test results now offered in the MacAllister/Caterpillar fluid analysis program. Knowing what the Particle Count test does is important to understanding ISO Codes.
First, Spectrographic Analysis is the fluid analysis test that identifies the specific metal or alloy that make up particles. So, over the course of several samples, it can spot particles of various metals that may be increasing in volume; this often signals potential problems. And by identifying the kinds and combinations of metals, it can generally point to the specific wearing component. But Spectrographic Analysis can only handle particles in the oil up to about 10 to 15 microns in size. So it’s blind to larger particles that can often signal an impending failure.
Particle Count now comes into play; it can quantify particles from one micron to greater than 200 microns in size. So it can detect additional signs of abnormal wear and dirty oil that Spectrographic Analysis may not catch. But it counts all particles, both metal and nonmetal, and can’t distinguish between the two. This is where the two methods complement each other: Spectrographic Analysis by quantifying and identifying specific metal wear particles below 15 microns; Particle Count by quantifying particles larger than can be detected by Spectrographic Analysis.
Particle Count has been used for many years by the fluid power industry to monitor debris levels in close-tolerance hydraulic systems. Its ability to warn of severe wear across a wide range of materials and micron sizes makes it a very useful tool in trending wear debris levels in most construction equipment compartments: transmissions, final drives, pump drives, hydraulics, etc.
An Efficient Partnership
Together, Spectrographic Analysis and Particle Count form an efficient partnership in identifying abnormal wear. Here’s how. The small metal particles that Spectrographic Analysis sees may rise sharply and then level off. But at the same time, large particles may show a sharply rising trend, signaling a failure in progress, one that only Particle Count can spot because of the size of the particles. So Particle Count sounds the alarm on abnormal wear and impending failure. Then, Spectrographic Analysis, by identifying the wear metals that rose and then leveled off, can point to the specific component in trouble.
- Diameter of a human hair – 80 microns
- Talcum powder – 15 microns
A micron is a metric measure equal to one millionth of a meter, or 1/25,000th of an inch. The smallest particle visible to the naked eye is 40 microns across. A human hair is 80 microns in diameter, and a single grain of talcum powder is 15 microns. Typical clearances in hydraulic systems are 10-30 microns.
Comparing Apples to Apples
Any valid measuring system must give consistent results calibrated the same way, time after time. This is crucial to measuring contamination because it enables interpreters to identify wear trends in consecutive samples from a single machine. It also enables component cleanliness targets to be set and accurately monitored. Both are important considerations in making repair-before-failure decisions.
Understanding Particle Count
Particle Count is reported in the number and size (in microns) of particles in a volume of fluid, using a valid particle counting system. Particle Counts are divided into size ranges or “channels”, each based on a specific size particle. Figure 1 shows a typical array of such channels and sample particles per milliliter results. These channels can be varied to report on any particle size relevant to the fluid or machine system involved.
(Fig.1) ISO CODE 23/21
|Channels (micron)||Particle Count||ISO CODE|
Particle Count Data is reported as the number of particles greater than a certain size. Bear in mind that the particle count for each channel includes all the particles in all the larger channels as well. Note: This data shows only particle size, not the specific particle composition (metal or nonmetal).
By trending this information over a series of samples, changes in the concentration of particles by size can be used to spot abnormal wear and forestall problems before they turn into failures. Then, Spectrographic Analysis on the same samples can often identify the metal makeup of the particles involved and point to probable components that might be heading for failure.
ISO Codes are a simple way to quantify particulate matter by size. These codes were established by the International Standards Organization (ISO), a worldwide federation of national standards bodies, and are the most widely used method for identifying fluid cleanliness. In our business, they apply to all non-engine lubricating fluids, with one of the greatest benefits accruing to close-tolerance hydraulic systems.
Here’s how ISO Codes work
Under the ISO Code system, 28 code numbers are set up, each representing a given range of particles per milliliter, ranging from 0.01 to 2,500,000 particles. The smaller the code number, the fewer number of particles. You’ll note that the size of each code range is double the number of the range that precedes it.
For example, ISO Code 10 has a range of 5 particles, ISO Code 11 has a range of 10 particles, ISO Code 12 has a range of 20, etc. This means that each one-step increase in ISO Code (i.e. going from 11 to 12) indicates the fluid is twice as dirty (in those sizes) as the preceding code.
Using the ISO Codes
The governing ISO standard (ISO 4406) establishes a two-factor code (X/Y) to express fluid cleanliness. The first factor (X) represents the number of particles larger than 5 microns and the second (Y) stands for the number of particles larger than 15 microns.
- X = number of particles larger than ()5 microns
- Y = number of particles larger than () 15 microns
For example, if in a given sample the particles/volume of 5 micron particles is 1350, and the particles/volume of 15 micron particles is 105, the ISO Cleanliness Code would be 18/14.
The 5 and 15 micron sizes were picked because the smaller size indicates wear particles that can cause “silting” in the fluid (and whose specific metal makeup can be read by Wear Metal Analysis), while the 15 micron size particles can indicate the presence of rapid wear and potential early failure.
This format, the 5 micron range first, the 15 micron range second, separated by a slash, is the universal signature for expressing a fluid’s ISO Cleanliness Code.
An ISO Code is a kind of cleanliness “shorthand” that’s easy to work with, an instant identifier that sums up oil contamination in only two numbers. As those numbers change between tests of samples from the same compartment, they can be the first indication of trouble. And such changes would be the signal to get a complete channel breakdown and compare it to Wear Metal Analysis data to identify a problem.