FED-STD-791D
4.1.4.2 Heat loss from the test oil system has been minimized by placing a 0.6-cm
(1/4-in) insulating box around the test oil tank. For screening tests at 149C (300F) oil-in
temperature, no other insulation is usually used. However, at 176C (350F) and 204C (400F)
oil in temperature, the test oil lines are wrapped, if necessary, with 2.5-cm (1-in) wide insulating
tape. In addition, insulating covers are placed over the test oil pressure pump housing. The
amount of insulation required is fixed for any individual system by the oil-in temperature
requirements for each test. For all types of operation the test oil tank is vented to atmosphere,
although plant exhaust suction systems are permissible as long as suction pressures do not
exceed 12.7 cm (5.0 in) of water. Normally, the test tank vapor space is slightly pressurized (0 to
0.76 cm [0 to 0.3 in] Hg) due to back pressure from vapor condensers in the vent line.
4.1.4.2.1 Only stainless steel tubing or pipe lines and fittings (including sump below
head) should be used in the test oil system. No insulation is required on scavenge lines but is
required on pressure lines and pump housings, as necessary to maintain the test oil temperature
conditions; however, the test oil in the thermocouple tee should be well insulated at all times.
The tee should be located not more than 7.6 cm (3 in) from end cover and should be large
enough to provide an oil annulus around the thermocouple. The tip of the thermocouple should
be located in the center of the tee. A 40-mesh filter screen (stainless steel, Erdco P/N 1RB 2007
S.S. for type 1-1/2 test conditions) should be used in the test oil scavenge filter housing which
should be located between the bearing head and scavenge pump.
4.1.4.3 Test oil tank.
4.1.4.3.1 Overall configuration. The overall configuration and general construction
details of the test oil tank should conform to the detailed Erdco Part No. 01RB2160. The tank
and baffle is constructed from AMS 5504C material; (AISI 410) 12.5% chromium steel sheet
and welding rod. Baffle plate height should be checked and adjusted if necessary to insure that
the top of the plate is 12.1 cm (4-3/4 in) from the botom of the tank. The top of the stirrer
propeller is to be even with the top of the baffle plate as determined by a straight edge.
4.1.4.3.2 Cover gasket material. A Teflon sheet gasket or equivalent cut to match the
outside flange dimensions should be used between the cover and mounting flange around the top
of the tank.
4.1.4.3.3 Stirrer and stirrer mounting. A Lightning Model L 1/30 hp motor having a
no-load (in air) shaft speed of 1800 rpm should be used in conjunction with a 5.1 cm (2.0 in)
diameter, three-blade propeller.
4.1.5 Air system. Saturated air is metered to the test oil compartment in the bearing
head. The air supply for the test bearing compartment should be shop air connected in the
following sequence; air supply to pressure regulator to flow control valve to rotameter to water
saturator to water separator tank to end cover fitting on bearing head. The air directed through
the end cover (at about 11 o'clock or 1 o'clock on the same diameter as the test oil jet) into the
bearing compartment is used primarily to control the pressure drop across the seal so as to insure
against oil transfer from the support section into the test oil section. A 1/4- H 1/8-in tubing to
pipe fitting should be used for the metered air supply to the rig.
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