FED-STD-791D
6.5.3 After the oil flow is set, the following conditions are allowed to stabilize:
121.1 . 4C (250 1 2F)
Oil-in temperature
600 20 mL/min
Oil flow rate
10,000 rpm 200
Bearing speed
Radial load
351.6 kPa (2224 N) [51 psig (500 lb)]
Support-oil-in-temperature
71.1 to 82.2C (160 to 180F)
Support-oil pressure
551.6 to 689.5 kPa gage (80 to 100 psig)
Gearbox-oil pressure
172.4 to 206.8 kPa gage (25 to 30 psig)
Airflow to end cover
0.165 0.01 L/sec (0.35 0.02 cfm)
Pressure drop across seal
0.76 to 1.27 cm (0.3 to 0.5 in) of test oil (test
compartment higher)
After the foregoing conditions stabilize, the run is continued until the test- bearing temperature
from the highest reading thermocouple stabilizes (about 1 h). This temperature is then noted and
used as an indication of the mechanical condition of the bearing. Previous tests on bearing
stabilization at a 121.1C (250F) oil-in temperature to the jet indicate that a temperature range
of 148.9C (300F) is normal for a properly functioning 100-mm test bearing. Higher
stabilization temperatures indicate the test-bearing condition is questionable, and the bearing
should probably be replaced before continuing with the test.
6.5.3.1 Once the test bearing has reached a satisfactory stabilization temperature, the
setting on the West controller for the test-oil heaters is increased to raise the bulk-oil temperature
to required value. The uppermost sump band heater is controlled by a manual on-off switch, not
the West controller. This heater is used only to accelerate the heating rate when a sump
temperature of 232.2C (450F), or above, is employed. The heater is not actuated until a sump
temperature of 204.4C (400F) is reached, and is deactivated when the desired sump
temperature is achieved. The bearing heater should be turned on simultaneously with the change
in sump heater setting to bring the bearing outer race temperature (max) to the required
temperature. 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 West temperature controller.
6.5.3.2 When the required bearing and sump oil temperatures are reached, the test-oil
flow rate is again checked and adjusted as necessary to maintain 600 mL/min. The sump
vent-gas flow is also measured at this time. The scavenge pump motor speed is adjusted to
obtain a flow of 0.24 0.01 L/sec (0.5 0.02 cfm).
6.5.4 Test cycle. The 48-hour test is conducted in three 16-hour operating periods. A
fixed shutdown period consisting of a minimum of 4 h and a maximum of 8 h is observed
between each 16-hour operating period. Run time begins counting when the test-oil heaters are
turned on, including bearing stabilization time. Test time stops when the test-oil heaters are
deactivated. Except for emergency stops, all shutdowns are made in accordance with the
detailed procedure subsequently outlined.
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