Sullair LS-200S Operator's Manual And Parts List page 21

Figure 2-5D Control System Diagram- MODULATION
line pressure will rise above 100 psig (6.9 bar), and
a pressure regulator starts feeding an air signal to
close the inlet poppet valve, throttling the air enter-
ing the compressor and thereby reducing the air
delivery. The air throttling of the inlet poppet valve
system increases proportionately with a rise of line
pressure from 101 to 110 psig (7 to 7.6 bar).
MODULATING MODE WITH OPTIONAL SPIRAL
VALVE - 100 to 110 PSIG (6.9 TO 7.6 BAR)
Refer to Figures 2-5A and 2-5D. As air demand
DESCRIPTION
drops below the rated capacity of the compressor,
the line pressure will rise above 100 psig (6.9 bar).
As a result, the differential pressure regulator for
the spiral valve gradually opens, applying air pres-
sure to the spiral valve actuator. Air pressure at the
actuator expands the diaphragm. The rack, in turn,
engages with the pinion mounted on the spiral
valve shaft assembly. This results in a rotary
motion. As the spiral valve rotates, it starts opening
the bypass ports gradually. Excess air is then being
Section 2
15