FED-STD-791D
6.5.1 Throughout the entire test the variables for different test severities (types 1, 1-1/2,
and 2) as shown in Table I should be controlled within the limits specified.
6.5.2 Initial test oil jet calibration. To calibrate the test oil jet, the test tank should be
heated until bulk oil temperature is about 149C (300F). Turn on air to the end cover. Then the
test oil and support oil pumps are turned on, and the rig speed increased to 10,000 rpm. The rig
speed should be brought up immediately after oil circulation is started as the screw thread seal
depends on relative motion for its sealing action. The previous setting on the test oil pressure
pump or a minimum of 69 gage kPa (10 psig) oil pressure at the jet should be used to insure
against possible oil starvation during this initial startup. The pressure drop across the seal is
maintained at 0.8 to 1.5 cm (0.3 to 0.6 in) of test oil by making fine adjustments to the gear box
vent valve. Under these conditions of air flow, the pressure in the test compartment should be
0.25-0.51 cm (0.1-0.2 in) of test oil above rig room pressure conditions. As soon as a 121C
(250F) oil temperature at the jet has stabilized, a minimum of two separate flow checks of
one-minute duration each should be made at the three-way valve position on the pressure side of
the scavenge pump. The oil pressure at the jet should be adjusted using the variable speed drive
unit on the test oil pump until the jet oil flow is 600 mL/min. Once the flow rate of 600 mL/min
is established for an oil, the flow at this condition is maintained constant during the test.
6.5.3 After the oil jet calibration step, the following conditions are allowed to stabilize:
121 C
250 F
Oil-in temperature
Oil flow rate
600 " 30 mL/min
600 " 30 mL/min
Bearing speed
10,000 " 100 rpm
10,000 " 100 rpm
Radial load
51 psig (500 lb)
352 gage kPa (2220 N)
Support oil-in temperature
160-180 F
71-82 C
Support oil pressure
80-100 psig
552-689 gage kPa
Gear box oil pressure
25-30 psig
172-207 gage kPa
Air flow to end cover
9.9 "1.4 L/min
0.35 " 0.05 cfm
Pressure drop across seal
0.8-1.5 cm of test oil (test
0.3-0.6 in. of test oil (test
compartment higher)
compartment higher)
6.5.3.1 After the foregoing conditions stabilize, the run is continued until the test bearing
temperature from the highest reading thermocouple levels off (about one hour). 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 C (250 F) oil-in temperature to the jet indicate
that a temperature range of 149 C to 177 C (300 F to 350 F) is normal for a properly
functioning 100-mm Erdco test bearing. Higher stabilization temperatures indicate the test
bearing condition is questionable and the bearing should probably be replaced before continuing
with the test.
6.5.4 Once the test bearing has reached a satisfactory stabilized temperature, the
temperature setting on the temperature controller on the test tank should be increased to raise
bulk oil temperatures to about 28 C (50F) higher than the desired temperature of the oil at the
jet (149C [300F] for the test of type 1 lubricants, 177C [350F] for the type 1-1/2 lubricants,
and 204C [400F] for the test of type 2 lubricants). In order to reduce the length of warmup
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