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|  MIL-T-21578A
Temperature control - Automatic controls shall be pro-
3.4.5.1
vialed for heating and cooling the test fluid and shall maintain the set tempera-
during constant and transient operation.
ture within
Manual temperature control - Manual controls shall be
3.4.5.1.1
furnished only to trim the hot and cold water supply for better flow control and
for use as shut-off valves.
3.4.5.1.2
Span - The span of automatic temperature-control adjust-
ment shall be as specified in the detailed specification,
3.4.5.1.3
Operation (control) - The automatic temperature control
and steam from +
to
shall operate with water from + 40"F to +
3.4.5.2
Manual operating controls - All controls shall be select-
ed and arranged to provide a maximum of convenience in operating ease, to reduce
test time and operator fatigue,
Location - All controls shall be located so as to permit
3.4.5.2.1
all phases of the test to be accomplished by one operator from the front of the
test equipment.
Remote operation - Control valves larger than 3/4-inch
3.4.5.2.2
port size, shall be remotely operated by air with regulator valve located on the
front panel. The control/valve shall be designed for continuous operation with
compressed air at 150 psi. The controls shall be such that in the event of elec-
trical or air failure the valve will be returned to "rest" or "safe" position
automatically (see 6.3.3(1)).
Shut-off and control valves - The handle motion of the
3.4.5.2.3
valve shall not exceed 90 degrees of rotation between extreme positions. Handle
loads shall be minimized by the use of ball thrust bearings or by balanced pres-
sures. Detents or nameplates shall be provided to identify correct handle posi-
tions. The flow passage diameters in the valves shall be equal to or greater
than the internal diameter of the piping to which they are connected. The valves
shall so operate that no undue hydraulic shocks or surges shall result from their
use to change flow volume or direction, The maximum allowable torque requir-
ed to operate manual-control valves shall not exceed 40 pound-inches. Push-pull
types of valves may be used provided they meet applicable requirements (see
6.3.3(m)).
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