Temperature Selector Valve; Temperature Selector Indicator Knob - Aerotech BT 400-46 Installation And Operation Maintenance

Section 4
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4.20

Temperature Selector Valve

4.21 Manual adjustment of the temperature selector valves within the operating range (150°F to 280°F)
applies motion through a pressure cone (see figure 4-4) to an inverted spring cup which forms the holder
for the needle assembly. The resulting movement of the needle seat orifice gives a smooth, continuous
regulation of fuel flow throughout the normal operating temperatures. A similar control of fuel is obtained
by upward and downward movement of the diaphragm. The diaphragm is spring loaded to the point
where a very slight additional upward pressure will result in further opening of the valve and increase the
flow of fuel in the by-pass line. This additional pressure is supplied by the expansion of the thermostatic
medium in the heat sensing element located in the discharge air stream. This pressure applied to the heat
sensing element located in the discharge air stream. This pressure applied to the diaphragm balances the
fuel flow to the selected temperature.
4.22 Adjustment of the valve for any discharge temperature results in an initial fuel discharge greater than
needed to maintain the selected temperature. The resulting increased heat output of the combustor brings
the heater up to the selected temperature rapidly. As the discharge temperature rises, the action of the
temperature sensing element opens the valve further, increasing the fuel flow in the by-pass line, thereby
decreasing the nozzle fuel discharge, consequently reducing the combustor heat output. The discharge air
temperature overshoots the selected temperature, then cycles about this temperature until a stable
condition is reached. Selecting a new temperature results in the same type of hunting action until
stabilizing at the new temperature.
4.23

Temperature Selector Indicator Knob

4.24 The temperature selector indicator knob is mounted on the control panel next to the temperature selector
knob. The approximate temperature is indicated by the pointer. When the temperature selector knob is
rotated, a pinion on the shaft engages a pinion on the temperature selector indicator knob shaft and rotates
the knob in direct relationship to the temperature selector valve.
AEROTECH HERMAN NELSON INTERNATIONAL INC.
100 Eagle Drive, Winnipeg, Manitoba Canada R2R 1V5
Phone: 204-633-1999 (24 Hours) Fax: 204-694-1612 Email:
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