TM 5-4310-386-14b. NormalOperation.The drain valves are connected in cascade and operated pneumatically via a normally closed 3-way solenoid valve (12) actuated by an electrical signal. The required control air applied to the solenoid valve is takenfrom the inlet to the second stage cylinder. The control pressure is approximately 72.5 psi (499.88 kPa). The control airfor the condensate drain valve for the oil and water separator (11) is taken from the intermediate filter (6). At compressorstart, both condensate drain valves (13) and (14) are open. At start-up of the compressor, the 3-way solenoid valve (12)is energized and opens. Due to the pressure built up by the compressor operation control air flows into the condensatedrain valves (13) and (14). The valve-pistons (16) are pressed onto valve seats (17) and the condensate valve closes.c. CondensateDrain.Every 15 minutes the solenoid valve (12) is energized for approximately 6 seconds. Solenoidvalve (12) closes the control air path from the second stage inter-filter (6). The servo-pistons (16) of the condensatedrain valves are unloaded, and the control pressures are vented through the relief port of the solenoid valve. The pistonsof the drain valves are raised, the valves open, and the condensate is drained.d. StartUnloading.The unloading during the starting phase of the compressor is effected due to the lack of control airimmediately after switching on the unit. After the compressor has attained nominal speed, control air flows through theopen solenoid valve (12) to the condensate drain valves (13), (14), and (15). These valves close and the compressordelivers air to the consuming device.e. StandstillDrainage.At compressor shut-down, solenoid valve (12) is energized and vents condensate drain valves(13) to (15). The valve pistons are raised by the residual pressure within the filters and separators. The valves open,and the filters are drained at standstill of the compressor unit.1-7/(1-8 blank)
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