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|  MIL-T-21578A
Recharging the accumulator - An air valve in accordance
3.4.3.9.4
with MS28889 shall be provided and shall be installed in an easily accessible
location for recharging the accumulator.
Instruments -
3.4.4
3.4.4.1
Flowmeters (fuel) - Flowmeters shall be as specified in
the detail specification,
3.4.4.1.1
Flowmeter graduations - Meter tubes and scales of var-
iable-area glass tube (direct reading) meters shall have logarithmic character-
istics to provide uniform percentage readability at all points on the scale, and
shall be calibrated in pounds per hour with at least 0.5 percent graduations. The
type fluid to be used shall be as specified in the detail specification. One half
of the percent of instantaneous flow at any point shall not be less than 0.625 inch.
Float position readings to the nearest scale graduation shall not exceed 0.5 per-
cent of the indicated flow. The lighting for the direct reading flowmeter shall be
behind the glass indicating tube(s) with a translucent material in between. The
illumination shall be evenly distributed over the translucent surface. The scales
shall be of translucent material. If the flowmeter is to be calibrated for MIL-F-
7024 fluids, the scale for Type I fluid shall be white and the scale for Type 2
fluid shall be green. If calibration for both Types I and 2 fluids are required on
the same test equipment, the white scale shall be on the right-hand side of the
tube and the green scale on the left-hand side of the tube. All other fluid scales
shall be white.
3.4.4.1.2
Accuracy - The flowmeters shallhave an instantaneous
percent when utilizing a fluid within the specified density,
accuracy within
viscosity, and temperature limits (see 6.3.3(h)).
Line pressure - Flowmeters shall be designed for a line
3.4.4.1.3
pressure of 50 psi, The meter shall withstand a leak test of 150 percent of the
maximum operating pressure (see 6.3.3(i)).
Pressure drop - Maximum pressure drop through the flow
3.4.4.1.4
meter or through a series of flow meters shall not exceed 8 psi. A back pres-
sure valve may be used for the suppression of vapor release and bubbles within
the instrument (see 6.3.3(j)).
3.4.4.1.5
Vent valves - The flowmeter shall have provisions for at-
taching vent valves to each tube which discharge through visible drip indicators
that return to the main fluid reservoir. The vent valves, indicators, and return
lines need not be component parts of the meter.
17
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