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|  MIL-T-21578A
3.4.4.4
Motor and pump tachometer - The range, degree of
accuracy, size, and type of tachometer shall be as specified in the detail
specification. Electrical components shall be easily removable by plug-in
type construction and shall be contained in one chassis which can be mounted
in a non-hazardous area up to 500 feet from the hazardous test area so that
no electronic circuity other than the indicator need be located in the hazardous
area,
3.4.4.4.1
Calibrating - Provisions shall be made for checking the
calibration of tachometers, other than electronic, without removal from the
stand either by checking the shaft speed with the hand tachometer or by incor-
poration of a common junction box with disconnect plugs for checking with
auxiliary test equipment.
3.4.4.5
Timers - Where precision timers are required, the timer
shall be self contained and shall not require an external source of frequency con-
trol.
3.4.4.6
Temperature indicators - Temperature indicators shall
be of a type and range as specified in the detail specification,
3.4.4.7
Pressure gages - All panel mounted pressure gages shall
be recess-type provided with mounting flange at the front of gage. The mounting
flange (and dial) shall not extend more than 5/8-inch beyond the external surface
of the panel. All gages shall incorporate a safety blow-out device to prevent blow-
out through the face of the gage. The safety blow-out device shall automatically
relieve the gage case-pressure should it reach l/2-psi due to gage failure. The
pointer shall be adjustable from the face of the gage. Stainless steel or nylon
movements shall be required on all gages. Gages subjected to continuous surges
and extreme pressure fluctuations shall be protected by a hydraulic damper. The
type, size, range, and accuracy of pressure gages shall be as specified in the de-
tail specification. The dial pointer shall be separated from the gage movement
such as to prevent rupture through the front of the gage in the event of gage
failure.
3.4.4.7.1
Mounting - Gages shall be mounted utilizing screws and
tapped holes to permit removal from the front of the panel by one man.
Connections - Gages shall be connected to the panel with
3.4.4.7.2
flexible hose of sufficient length to permit removal and installation from the front
of the panel.
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