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this valve should be near ambient tempera-
ture while operating. In Figure 8, the tank
line temperature of the manual valve is 99.3
degrees F, indicating that the valve is closed.
9. Check the Temperature
of the Accumulator Shell
Check the temperature at the top (K)
and bottom (L) of the accumulator shell.
e bottom half of the accumulator should
be warmer than the top half. e heat is
generated by the friction of the oil as it flows
in and out of the shell. On a bladder type
of accumulator, the rubber bladder will be
compressed to the top part of the shell. When
the pressure drops in the system, the bladder
will expand and force oil out of the accumu-
lator. If the temperatures are nearly the same,
this indicates the dry nitrogen pre-charge has
leaked out, the pre-charge is higher than the
pump compensator setting or the bladder has
ruptured. Piston accumulators will show a
greater difference in heat than bladder types.
10. Check the Oil
Temperature in the Reservoir
Finally, check the oil temperature (M) in
the reservoir. A temperature gauge usually is
included in the sight glass. Over time, the
sight glass may become discolored, or the
thermometer may fail. To obtain a consistent
oil temperature reading, make a mark or draw
a target on the side of the reservoir. In this
manner, the oil temperature can be checked
in the same location each time.
While this article has focused on tempera-
ture checks that can be made on the power
supply, there often will be other pressure
control, directional and manual valves located
away from the power supply. Additional accu-
mulators may also be used near the machine.
Performing these tests can help identify an
issue before it becomes serious. If a shutdown
of the machine does occur, the recorded infor-
mation will be valuable when troubleshooting
the system.
ML
About the Author
Al Smiley is the president of GPM Hydraulic
Consulting Inc., located in Monroe, Georgia.
Since 1994, GPM has provided hydraulic
training, consulting and reliability assessments
to companies in the United States, Canada, the
United Kingdom and South America. Contact
Al at gpm@gpmhydraulic.com.
Figure 9. The bottom half of an accumulator (left) should be warmer than the top half (right).
