MIXING: Mixing different brands of oil is not recom-
mended. Various companies use different additive
packages, which when mixed together, may cause
problems in a hydraulic system. This type of problem is
rare but can cause sludge which can plug the filters or
acid which will etch the pump plates.
PRE-FILTER: Oil should be filtered through a 10 mi-
cron nominal filter before it enters the hydraulic sys-
tem. New hydraulic fluid as received by the user is
generally NOT in a satisfactory cleanliness condition
for long component life.
OIL MAINTENANCE: Optimum life from hydraulic
equipment can only be obtained with proper hydraulic
oil maintenance. This includes checking the oil every
three to six months. An oil should be checked for vis-
cosity, oxidation, water content, contamination and
copper particles. A record should be kept of each
check to detect signs of progressive deterioration. Oil
samples should be taken with the system running at
normal operating temperature. It is important to use
good technique in obtaining an oil sample. The exact
same procedure should be followed each time an oil
sample is taken. Most fluid suppliers will provide assis-
tance in analyzing your oil sample. The following are
some guidelines to use in this analysis.
Viscosity - Many hydraulic fluids will shear or thin out
with use. The viscosity at each check should be com-
pared to the viscosity when new. At no time should the
viscosity be less than 45 SSU at 210°F. If viscosity is
less than 45 SSU at 2I0°F, the oil must be replaced im-
mediately.
Oxidation - Oil oxidation will occur with age and use
and is evidenced by a change in color and/or odor, in-
creased acidity, and possible formation of sludge, gum
or varnish in the system. The rate of oxidation increas-
es significantly with operations at temperatures over
140°F (60°C). The oil should be checked more often if
operation is at high temperature. The oxidation pro-
cess increases the acidity of the fluid and is measured
by a neutralization number. The oxidation process is
typically slow at first and then increases sharply in the
final stages of complete oxidation. A sharp increase
(by factor of 2-3) in a neutralization number is a good
indication that the fluid is reaching the limit of its oxida-
tion life and should be replaced.
Water Contamination - All hydraulic oils in the following
charts will readily separate water which will settle to the
bottom of the reservoir. This water should be drained
off. The water that is measured in the oil sample will be
dissolved water. This should be less than .05%. If it is
greater than .05%, the oil in the system should be
drained and replaced.
Particle Contamination - Excess contamination in a hy-
draulic system will greatly shorten the life of pumps
and motors. Your oil sample analysis will show the
number of particles per milliliter greater than a given
micron size. The number of particles in your sample
should be less than the following:
Particle Size No. of Particles/Milliliter
10 micron or larger 3,000
20 micron or larger 300
30 micron or larger 100
40 micron or larger 30
50 micron or larger 10
100 micron or larger 1
If your oil sample shows numbers greater than in the
chart, your hydraulic system is contaminated. The sys-
tem should be checked for broken or torn filters,
plugged filters, stuck filter bypass valves and so forth.
Continued operation with particle counts greater than
those shown in the chart will result in short pump and
motor life.
Copper Particle Counts - The oil sample analysis
should include a copper particle count in parts/million.
This number should normally be less than 100. A high
copper particle count indicates that a gear pump or
motor is rapidly deteriorating. A count of 200 or more
would be cause for concern. The most important thing
to look for is a sudden increase in the copper particle
count. This indicates that a gear pump or motor has
suddenly begun deteriorating and a catastrophic fail-
ure can be expected shortly.
MAINTENANCE AND LUBRICATION
4 - 22 Revised: March 2005RT700 Series
To Next Page
Loading...
