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|  MIL-T-21578A
3 . 4 . 5 . 2 . 3 . 1 Hystersis - Valves shall not creep from selected posi-
tion and shall be free from hysteresis,
Needle valves - Needle valves shall be panel-mounted.
3.4.5.2.4
AH needle valves used shall show the manufacturer's operating pressure rating
stamped on the valve body, as well as an arrow showing flow direction. Needle
and packing shall be readily accessible from the front of the stand. The valve
knob or handle shall be installed on a square or milled flat-section of the valve
stem. Valves shall be of a type that can be disassembled for inspection, repair
or replacement of parts.
Automatic controls - Where it is necessary to control
3.4.5.3
pressure or flow to a constant value, automatic controls shall be used. A slight
amount of adjustment of the control will be permitted when it is necessary to
control within close limits over a wide range of operating conditions. Limits
and accuracy shall be as specified in the detail specification.
Automatic shut-off valves - Automatic shut-off valves shall
3.4.5.4
be inter-locked to operate automatically with the test equipment emergency-
disconnect controls. Automatic shut-off valves other than those in the flowmeter
system shall be pneumatic or solenoid actuated valves. In the event of test
stand power, water, or air failure automatic shut-off valves shall fail in the
safe position.
Test fixtures - Test fixtures for test equipment designed
3.4.6
to test only one type of accessory shall be furnished as component parts of the
equipment.
Multiple purpose - Test fixtures for test equipment designed
3.4.6.1
to test various types of accessories shall not be included with the
basic test equipment, with the exception of the base mounting fixture which shall
be furnished.
3.4.6.2
Location - Mounting pads and brackets for test fixtures
shall be conveniently located in relation to the related instruments and controls.
Test fixtures shall not interfere with the instrument and control adjustments that
are required during calibration.
Drive pad - All drive pads for testing driven components
3.4.7
shall be designed so that the mounting pad and spline adapter will be fully remov-
able and interchangeable with other sizes ofsplines and pads. The pads and splines
shall bc easily removed and installed from the front of the stand by one man. Pads
and splines shall be in accordance with AND 20001 and AND 20002, as applicable.
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