FED-STD-791D
controlled by a West type JP controller, or equivalent, with a watt-hour meter connected between
the heaters and the controller to monitor total power input. The test oil is pumped from the sump
by the variable-speed pressure pump to the 100-mesh filter housing. The lubricant then flows to
a tubing cross attached to the filter housing. One leg of the cross contains a bayonet
thermocouple measuring the test-oil-in temperature. One leg transmits fluid pressure to an
indicating gage and two pressure safety switch units connected in series. The latter units are set
with one unit at a minimum pressure of 34.5 kPa gage (5 psig) and one at a maximum pressure of
241.3 kPa gage (35 psig). In the event of a test-oil pressure excursion outside this range, the
applicable safety switch deactivates the main drive motor. The system protects against rig tieup
as a consequence of lubricant starvation in the event of test-oil pump failure, jet plugging, or
other equipment malfunction. The third leg of the cross delivers test oil to the jet and then to the
test bearing. The test oil is drained from the bearing head at two locations, G, as shown on
Figure 1. The front drain collects splash oil which does not pass through the bearing, whereas
the rear drain collects only oil that has gone through the bearing. Both drains feed into a fluid
accumulator via a single line leading to a three-way valve used for in-line sampling. The test-oil
line continues beyond this valve to a second three-way valve which permits routing of the oil to
an incorporated test-oil flow measuring system. The test oil next passes through a 40-mesh filter
and enters the scavenge pump prior to discharging into the sump.
4.2.4.1 Heat loss from the test-oil system is minimized by placing insulation on the sump
sides, base, and cover as identified on Figure 2. The test-oil-in lines and filter housing are
wrapped with a single thickness of Fiberfrax insulation, or equivalent, to reduce the differential
between test-oil-in temperature and sump temperature. Insulating in this manner will normally
result in a test- oil-in temperature slightly below the required bulk-oil (sump) temperature. If this
differential exceeds the allowed maximum, additional insulation thicknesses are applied. In
operation, the test-oil sump is vented to atmosphere.
4.2.4.2 The test-oil entering the sump is normally hotter than the bulk-oil in the sump.
A forced-air cooler, shown on Figure 2, is placed around the test- oil line section preceding the
test-oil-out filter to cool the lubricant as required. In some cases, it may be necessary to insulate
a portion of the scavenge line with insulating tape to maintain the desired oil temperature
entering the sump.
4.2.4.3 Only stainless steel tubing or pipelines and fittings are used in the test-oil system.
The fluid accumulator, filter housings, and sump are similarly constructed of stainless steel.
4.2.4.4 Test-oil sump. The overall configuration and construction details of the test-oil
sump conform to the detailed drawings specified in 4.1.
4.2.4.4.1 Sump cover seal. A 0.16-cm (1/16-in) thickness gasket of suitable
dimension is cut to seal between the sump flange and sump cover. Raybestos-Manhattan
A-56 gasket material, or equivalent is employed.
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