Atlas Copco XAHS 186 Cud PNE, Instruction Manual

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CONTINUOUS REGULATING SYSTEM
The compressor is provided with a
continuous regulating system and a blow-
off valve (BOV) which is integrated in the
unloader assembly (UA). The valve is
closed during operation by outlet pressure
of the compressor element and opens by air
receiver pressure when the compressor is
stopped.
When the air consumption increases, the
air receiver pressure will decrease and vice
versa. This receiver pressure variation is
sensed by the regulating valve (RV) which,
by means of control air to the unloader
assembly (UA), matches the air output to
the air consumption. The air receiver
pressure is maintained between the pre-
selected working pressure and the
corresponding unloading pressure.
When starting the compressor, the throttle
valve (TV) is kept closed via receiver
pressure. The compressor element (CE)
takes in air and pressure builds up in the
receiver (AR). The throttle valve (TV) is
closed. The air output is controlled from
maximum output (100%) to no output
(0%) by:
1. Speed control of the engine between
maximum load speed and unloading
speed (the output of a screw compressor
is proportional to the rotating speed).
2. Air inlet throttling.
If the air consumption is equal to or
exceeds the maximum air output, the
engine speed is held at maximum load
speed and the throttle valve (TV) is fully
open.
If the air consumption is less than the
maximum air output, air receiver pressure
increases and the regulating valve supplies
control air to throttle valve (TV) to reduce
the air output and holds air receiver
pressure between the normal working
pressure and the corresponding unloading
pressure. Unloading pressure = normal
working pr 1 bar (14.504 psi).
When the air consumption is resumed, the
blow off valve (BOV) closes and the
throttle valve (TV) gradually opens the air
intake and the electronic speed regulator
increases the engine speed.
The construction of the regulating valve
(RV) is such that any increase (decrease)
of the air receiver pressure above the pre-
set valve opening pressure results in a
proportional increase (decrease) of the
control pressure to the throttle valve and
the electronic speed regulator.
Part of the control air is vented to
atmosphere, and any condensate
discharged, through the vent holes.