Page 7 - Parker - The Handbook of Hydraulic Filtration

Contamination Types and Sources

Damage

If not properly flushed, contaminants
A B
A. Three-body from manufacturing and assembly will
mechanical
interactions can be left in the system.
result in interference.

B. Two-body wear is These contaminants include dust,
common in hydraulic welding slag, rubber particles from
components.
hoses and seals, sand from castings,
C D Stress raisers caused C. Hard particles can
by particle collisions and metal debris from machined com-
create three-body
wear to generate ponents. Also, when fluid is initially
more particles. added to the system, contamination is
D. Particle effects can introduced.
begin surface wear.
During system operation, contamina-
tion enters through breather caps,
Sources worn seals, and other system openings.
▼ Built-in during manufacturing and ▼ Ingested from outside the system System operation also generates inter-
assembly processes. during operation. nal contamination. This occurs as
component wear debris and chemical
▼ Added with new fluid. ▼ Internally generated during
byproducts react with component sur-
operation (see chart below).
faces to generate more contamination.

Generated Contamination

Abrasive Wear—Hard particles Erosive Wear—Fine particles in
bridging two moving surfaces, a high speed stream of fluid eat
scraping one or both. away a metering edge or critical
surface.
Cavitation Wear—Restricted
inlet flow to pump causes fluid Adhesive Wear—Loss of oil film
voids that implode causing allows metal to metal contact
shocks that break away critical between moving surfaces.
surface material.
Corrosive Wear—Water or
Fatigue Wear—Particles chemical contamination in the
bridging a clearance cause fluid causes rust or a chemical
a surface stress riser that reaction that degrades a
expands into a spall due to surface.
repeated stressing of the
damaged area.

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