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May - June 2018
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An infrared camera is
one of the best tools for
performing regular reli-
ability tests on a hydraulic
system. It is also invaluable when
troubleshooting heat, speed and pres-
sure issues. In any hydraulic system,
some lines will be at, above and below
the oil temperature in the reservoir.
e key is to know which lines should
be cool, warm and hot. If checks are
made when the system is operating
normally, a reference can be estab-
lished. By regularly conducting the
following tests, a faulty component
can be found, many times before it
shuts down the machine.
A schematic for a typical
hydraulic system is shown in Figure 1.
e circled letters indicate the points
in the system that should be shot and
recorded with an infrared camera.
1. Check the Suction
and Case Drain Lines
Check the suction and case
dra in lines of t he pump by
recording the temperatures at points
"A" and "B" in Figure 1. e oil in
the "A" line should be very near the
oil temperature in the reservoir. e
oil that flows out of the case drain
line (B), is the oil that bypasses
the internal components inside the
pump. Most piston pumps bypass
1-3 percent of the maximum pump
volume. Vane pumps may bypass as
much as 5 percent of the maximum
rated volume. For a 30-gallon-per-
minute piston pump, the amount of
oil in this line should be one-third
(1 gallon per minute). Because the
oil does no useful work, heat will
be generated as the oil bypasses the
internal pistons. is line, of course,
will be hotter than the oil entering
the pump through the suction line.
The suction and case drain
temperatures are shown in Figure
10 Ways to Check
Hydraulic Systems with
Thermal Imaging
HYDRAULICS
Al Smiley
|
GPM Hydraulic Consulting
J
C
A
B
D
AB RV
H
G
CV
HE
RF
F
E
M
I
K
ACC
MDV
To System
EDV
12
PSI
2000
PSI
PSI
2250
Figure 2. Images showing the suction and case drain temperatures
Figure 1. A schematic for a typical hydraulic system
"By regularly
conducting
the following
tests, a faulty
component can
be found, many
times before it
shuts down the
machine."