Installation Manual Series CF (excluding encapsulated screw compressors) 23042013 Rev. A / May 2007 12 of 60
4.2.4 Switch-off
Switch-off takes place intentionally upon ac-
tuation of the motor circuit breaker or by
means of safety cut out in the event of:
• A pressure behind the compressor of more
than p
2
+ 0.3 bar by contact manometer [6],
• A temperature behind the compressor of
more than 110 °C by quick-action tempera-
ture controller [7],
• a temperature in oil reservoir [9] of more
than 110 °C by quick-action temperature
controller [11].
Switch-off must be initiated at a
temperature of not more than
120°C.
For safety reasons the motor should be swit-
ched-off from No-load position.
If the motor comes to standstill before the
system is completely relieved, non-return val-
ve [8] prevents reverse motion caused by
backward pressure drop.
Oil stop valve [30] is generally open. If at
switching-off, the motor comes to standstill
before the system has been relieved, a pres-
sure difference occurs between the pressure
side of the compressor and the oil line of oil
stop valve [30] and closes oil stop valve [30].
This ensures that the compressor cannot be
filled with oil from the oil system due to the
pressure drop (risk of a liquid hammer when
starting-up again).
4.2.5 Oil system
Utilizing the pressure difference, the oil collected
in the oil reservoir/coarse separator is used to
supply the compressor with oil.
By means of adjustable throttle valve [31], the
oil injection amount into the compression
chamber (connection A) is adjusted in a way
to provide for the desired discharge tempera-
ture (between the dew point temperature and
110 °C).
By means of the thermostatic valve [29], the
oil intake temperature for the compressor
stage is kept approximately constant depend-
ing on operating condition and dew point.
Connection F is used to return the oil col-
lected in fine separator [14] into compression
chamber of the compressor. With minimum
discharge pressure, adjust throttle valve [34]
in a way that (visible on sight glass [33]) only
a small amount of air is returned with the oil.
Non-return-valve [35] prevents, that during
relief, oil from the compression chamber is
blown into the open through the fine separa-
tor and relief valve [16].
Non-return valve [25] prevents that oil flows
back from compressor and oil system into the
oil reservoir if, when switching from No-load
to Load, a pressure has already built-up in
the compressor whilst oil reservoir [9] is still
relieved.
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