FED-STD-791D
time required to reach the desired test oil jet temperature, the Calrod heater should be turned on
simultaneously with the change in test tank setting to bring the bearing outer race temperature
(max) to 260C (500F). At this point, the three thermocouples attached to the bearing outer
race should be checked to make sure that the thermocouple indicating the second highest
temperature is attached to the Temperature Controller. Improper hookup of the bearing
thermocouples will result in poor control of test bearing temperatures.
6.5.5 When the desired test conditions shown in Table I are reached, the test oil flow rate
is again checked twice and adjusted if necessary to obtain 600 mL/min flow at the three-way
valve position in the scavenge line. Then the 100-hour endurance test is begun. These data are
recorded on a multi-channel strip chart continuously during the course of the test.
6.5.6 Test cycle. The 100-hour endurance test is run so that there is at least a seven-hour
shutdown period out of every 24 h of operation. Except for emergency stops, all shutdowns
should be made in accordance with the detailed procedure as outlined in 6.6.4.Warmup time
following shutdown periods is considered part of the 100-hour endurance test time.
6.5.7 Used oil analysis. The following laboratory tests are run on the new and used oil
samples:
ASTM method
50 mL samples
Test
Viscosity at:
37.8C (100F), cs
D 445
X
98.9C (210F), cs
D 445
X
D 664
X
Neutralization No.
6.5.8 Test oil flow rate checks. During operation the test oil flow rate should be checked
at the three-way valve in the scavenge line twice every start-up. For convenience, a 1000-mL,
borosilicate glass graduated cylinder should be used to collect the test oil during the flow check.
The volume of oil collected in a one- or two-minute period should check the original volume
flow in mL/min within "5.0%. In order to prevent too large a drop in test oil level in the tank
during flow checks, a maximum continuous flow period should be 2 min. The hot test oil
collected in the glass graduate should be dumped back into the test tank after each flow check.
With the friction type variable speed drive unit on the test oil pressure pump, it is not possible to
obtain a non-slip drive on the pump after oil pressures reach about 276 gage kPa (40 psig). At
this point the test oil will usually have become so viscous it can no longer be effectively pumped
and the test should be considered ended.
6.5.9 At the completion of the 100-hour endurance test, the test bearing is restabilized at
121C (250F) oil-in temperature to determine the relative change in stabilized temperatures
compared to the results obtained at the start of the test. These data can be used to determine the
change in frictional characteristics of the bearing resulting from metal wear or excessive oil
deposits.
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