TM 5-4310-386-14
b. Normal Operation. 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 taken
from the inlet to the second stage cylinder. The control pressure is approximately 72.5 psi (499.88 kPa). The control air
for the condensate drain valve for the oil and water separator (11) is taken from the intermediate filter (6). At compressor
start, 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 condensate
drain valves (13) and (14). The valve-pistons (16) are pressed onto valve seats (17) and the condensate valve closes.
c. Condensate Drain. Every 15 minutes the solenoid valve (12) is energized for approximately 6 seconds. Solenoid
valve (12) closes the control air path from the second stage inter-filter (6). The servo-pistons (16) of the condensate
drain valves are unloaded, and the control pressures are vented through the relief port of the solenoid valve. The pistons
of the drain valves are raised, the valves open, and the condensate is drained.
d. Start Unloading. The unloading during the starting phase of the compressor is effected due to the lack of control air
immediately after switching on the unit. After the compressor has attained nominal speed, control air flows through the
open solenoid valve (12) to the condensate drain valves (13), (14), and (15). These valves close and the compressor
delivers air to the consuming device.
e. Standstill Drainage. 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.
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