13-21-615 v01 Page 37
304EBF797-A
(Ref. Drawing)
Figure 4-4 Turn Valve, Electra Saver Only
Turn Valve
(Electra Saver only) (Figure 4-4) The turn valve is a helical valve which, when rotated, opens
and closes a series of ports cast into the compressor cylinder. When these ports are open, they direct
some of the air which would otherwise be compressed back to the inlet, reducing both capacity and
power consumption.
Turn Valve Actuator
(Electra Saver only) - The turn valve actuator is a rotary rack and pinion device
which positions the turn valve according to system demand. Filtered oil from the compressor sump is
directed to the outboard end of the two actuating cylinders to move the rack and rotate the valve.
Located on the ends of the cylinders are adjusting screws which limit the travel of the actuator. When
looking at the rear of the compressor, the adjusting screw on the right on the compressor adjusts the fully
closed (full-load) position of the valve. The full load position of the actuator may be checked by removing
the adjusting screw at the unloaded end of the actuator (left side of the compressor) and using a rod to
push the pistons to the full load position. The rod must be clean and free of burrs and scale. Take care
not to scrape the cylinder walls when moving the pistons.
Solenoid Valves TVC and TVO
(Electra Saver only) - These valves control the position of the turn valve
in response to signals from the Governor Controller. With both valves de-energized, equal pressure is
applied to both ends of the actuator to hold it in its present position. If TVC only is energized, the right
side of the turn valve actuator is exhausted to the compressor inlet cavity, causing the turn valve to move
towards the full load position. If TVO only is energized, the left end of the turn valve actuator is
exhausted to the compressor inlet cavity, causing the turn valve to move towards the unload position.
Plant Delivery (System) Pressure Transducer
- This transducer is connected after the aftercooler. It
converts the pressure in the plant air system into an electrical signal for use by the Governor Controller
for modulation and control.
Separator (Discharge) Pressure Transducer
- This transducer is connected after the minimum
pressure valve. Its signal is used to monitor the condition of the air/oil separator and cooler.
