Atlas Copco MAS 200, Инструкция

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modulating control
In general, the modulating control system consists of:
• A control valve
• A bleed-off nozzle
• A throttle valve with a pneumatic actuator
Installation
The modulating control system needs an air net of a certain volume to operate in a stable
manner. An air net of 5000 l is deemed to be sufficient.
Working principle
A throttle valve is placed in between the air inlet pipe and the unloader valve. The air net
pressure is reduced by a control valve. The resulting control pressure is fed into the actuating
cylinder of the throttle valve.
If the air demand decreases, the net pressure will increase accordingly and the throttle valve will
close. This will result in a decrease in absolute pressure at the inlet of the compressor element
and consequently in a decrease in air delivery, reducing fluctuations in net pressure.
An increase in air demand will result in the same way in an increase in air delivery. This will result
in a net pressure staying within a narrow band. To protect the compressor element against too
high a pressure ratio the throttle valve has by-pass holes to guarantee a minimum air flow. In the
table below the minimum air flow as well as the number and diameter of the by-pass holes are
given.
Minimum FAD, modulating control :
Unit designation Pressure
(bara)
max.FAD
(l/s) min.FAD
(l/s) min.FAD
(%) number of
by-pass
holes d (mm)
MAS 200 10.4 529 140 26 2 22
Instruction book
18 APF219617