Contaminants in fluids [page 1 of 'ferrous particle problem']
Contamination is unwanted material in a system. Broadly, there are three contamination types:
Inbuilt - All systems will have inbuilt contamination left from manufacture, for example metal from the machining processes that was not flushed out during cleaning.
Ingressed - Ingressed contamination refers to external particles finding their way into the system. This can be from, for example, reservoir openings (poorly sealed units, or rust holes). It can also be from oil filling, both the method and contaminate in the new oil itself.
Generated - This refers to the contamination caused by wear processes as the machine operates, clearly the more inbuilt contamination the more wear contamination would be created.
Contamination therefore varies in size, type and amount dramatically from one system to another.
Contaminant effects
Contamination can compromise processes in a variety of ways, including shortening component or fluid life. Invariably, excessive contamination results in catastrophic failure. This is a well documented problem :
50% OF COMPONENTS NEED REPLACING THROUGH WEAR [Dr. Rabinowitz, Massachuesetts Inst. of Tech., 1981]
55% OF PROBLEMS ARE DUE TO PARTICULATE CONTAMINATION [DTI Survey of Hydraulic & Lubrication Equipment, 1983]
A BEARING WITH 100micron FILTERED OIL HAS 1/100th LIFE OF 3micron FILTERED OIL [Jackobson, SKF, 1987]
(1micron= one thousandth of a meter - the human eye can only pick out details down as small as 40microns)
Reduction of these types of contamination, and in particular, microscopic contaminant is absolutely key to deliver efficient processes.