Overview

Background/
Definitions

Topic
Introduction

Activity 1.1

Activity 1.2

Activity 1.3

Particle Counting Form

Assessment

Developer Bio

Background

In any industry that uses hydraulic systems and fluids, the proper performance of the equipment relies heavily on the control of any possible contaminants. Therefore, it is crucial to have at least a basic knowledge of these particles, their types and size ranges,  calculation methods of the number of contaminants present, and the level of contamination or cleanliness of the fluid, as well as the maximum levels of these particles allowed in any specific fluid.In some instances, even one contaminating particle over the maximum number allowed would cause severe damages to the machines and pumps, and eventually the "shut-down" of multi-million dollar systems. This not only affects the company involved and its clients, but may also have a major global effect in that industry.

Definitions

Principles of Microscopy

In order to have an accurate count of these particles, a microscope is required. A microscope is an instrument that can magnify the image of a very small object or specimen (in this case: particles).

Variations in Microscopy

There are many different types of microscopes used for different purposes (Academia and the Workplace):

1. Light Microscope: focuses the light source onto the specimen by a condenser lens and with the combined effects of the objective lenses and the ocular lens (eyepiece), the magnified image will be projected on to the eyes.
2. Electron Microscope: uses electron beams instead of a light source, focused through a specimen.
3. Other microscopes used include Fluorescence, Phase-contrast, etc.

In this module, we will only use the Light Microscope.

Magnification vs. Resolution
(Two important values in microscopy)

1. Magnification: refers to the enlargement value of the image or how much the image is enlarged compared to the real size of the object. Total magnification power equals the magnification power of each objective lens multiplied by the magnification power of the ocular lens (10x).     
   
   

   Objective lens mag.	Ocular lens mag.	Total mag.
   Scanning lens---4x	10x	(4x)(10x)=40x
   Low Power -----10x	10x	(10x)(10x)=100x
   High Dry--------40x	10x	(40x)(10x)=400x
   Oil Immersion---100x	10x	(100x)(10x)=1000x

We will use the first three objective lens systems in this course with one modification. Instead of a High Dry (40x) lens, we will need a 20x lens, which will give a Total Magnification of 200x.

1. The size ranges of the contaminating particles counted in this course usually falls at about 5 Microns or greater (with 20% variation).
2. Measurement Units: Microns or Micrometers.
3. Conversion Table: 1 cm = 0.01m = 0.4 inches; 1mm=0.001m;  1 micron = 0.001mm = 0.000001m. For example, a chicken egg falls just under 0.1m, where 1 micron is 0.000001m; or the smallest dot that you can make with the sharpest pencil is about 40 microns.
4. Types of contaminant particles: a wide variety of sources for these particles exist, such as droplets in the air, clothing fibers, air conditioning units, stainless steel particles from the machinery, insects, etc.

Sources

The sources used for this module are the standards used in the industries. These standards are "controlled copies" and need to be ordered.

1. ISO (International Organization for Standardization), which includes ISO 4406 "Methods for Coding the Level of Contamination by Solid Particles," and ISO 4407 "Determination of Particulate Contamination by the Counting Method Using a Microscope."
2. NAS (National Aerospace Standard) - "Cleanliness Requirements of Parts Used in Hydraulic Systems."
3. AS4059 Revision F - "Aerospace Fluid Power: Cleanliness Classification for Hydraulic Fluids."