FED-STD-791D
4.1.5.1 Air to the test head is metered through a rotameter. Prior to each run, the
rotameter is calibrated against a wet test gas meter for a flow of 9.90 L/min (0.35 CFM). The
procedure is to disconnect the air supply line at the fitting where the air enters the head and then
connect the supply line to a wet test gas meter which in turn discharges to atmosphere. A
mercury manometer is located immediately upstream from the rotameter. The settings of the
manometer and rotameter are observed and recorded for a wet test gas meter reading of 9.90
L/min (0.35 CFM). The air line is then reconnected to the bearing head and the previously
observed manometer and rotameter settings are maintained throughout the test.
4.1.5.2 Seal (test support). The screw-type seal (P/N IRBB-6204) should be vented to
the test cell at both top and the botom of the seal housing connections.
4.1.5.3 Connections for seal differential pressure measurement. The lines to the
manometer used to measure the differential pressure across the seal should be connected to top,
front of the bearing head, and the rear vertical surface of the bearing housing between 11 and 1
o'clock 2.5 cm (1 in) above the junction of the rear case with the main housing. After startup
there should be no venting of the manometer lines. In this connection, the pipe plug in the top of
the gear box, if used, should be removed and replaced with a small valve to insure atmospheric
pressure in the gear box and hence in the support system.
4.1.6 Fenwall thermostatic control switch (Cat. No. 17802-510 or equivalent) (-18 to
315C [0 to 600 F] normally closed). This switch should have a stainless steel sheath and be
located in end of tank opposite stirrer motor 10.8 cm (4-1/4 in) from bottom and on the center
line of the tank.
4.1.7 Heater unit. A Chromalox tubular heater unit (MT0345) having a rating of 4500
W, rated at 115-120 V should be series connected to a 220 V supply and controlled by means of
a differentiating type temperature controller or a suitable auto-transformer. Three thermocouples
installed 31.8 cm (12-1/2 in) from terminal end of tank should be used. All thermocouple lead
wire should be of the Ceramo, a metal-sheathed type. Test oil heater thermocouples are to be
attached to the tubular heater by clamps, welded shoes, or spot weld.
4.2 Graduated cylinder, borosilicate, 1000 mL.
5. MATERIALS
5.1 CAUTION: SOME MATERIALS ARE TOXIC AND HAZARDOUS. The
materials refer-ences and standards listed in this section must be handled carefully. Federal Test
Method 10000, Material Handling Safety Precautions, is a reference which lists all toxic and
hazardous materials cited in FTMS 791. The synonyms, life hazard, flammability, handling and
storage precautions, emergency treatment and measures, and spill practices of each chemical are
explained.
5.2 Lubricating oil, qualified under MIL-L-23699.
5.3 Dry cleaning solvent, (A-A-59601D).
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