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4. Design and functioning
24
Automatic operation (open-close operation)
•
When the pressure reaches the upper switching
point set on the network pressure sensor (-28 -
(B1)), solenoid valve (- 30 - (Y1)) is deenergised.
•
The pressure valve (-2.2-) closes because the lower
control space of the adjusting cylinder (-2.1.-) is
relieved by the deenergised valve (-30-(Y1)) the
upper control space is impinged with pressure via
the valve (-32-).
•
The oil separator tank is relieved to no-load
pressure (residual pressure) via the two valves (-31-
and -32-).
•
The screw compressor is now running in the offload
mode.
•
The cooling air ventilator (- 26 -) is switched on or
off in dependence upon the final compression
temperature.
•
When the pressure at the network pressure sensor
(- 28 - (B1)) does not fall to the set lower switching
point within the set motor run-on time (e.g. 120
seconds), the drive motor (- 3 -) and the cooling air
ventilator motor (- 26 -) are shut down and the
system is depressurised to atmospheric pressure.
•
The system is now in the “stand-by” mode and can
restart at any time when the network pressure falls
to the lower switching point (see section “Starting of
the system”).
•
When the pressure at the network pressure sensor
(- 28 - (B1) falls to the preset lower switching point
before the set motor run-on time has elapsed,
solenoid valve (- 30 - (Y1)) is energised again.
•
The unit now changes over to on-load operation.
4.5.2
System control ESM 37-ESM 50
(Fig. 3 b)
(See also operating instructions for the compressor
control GD Pilot MK)
Danger
The lower control area of the operating cylinder
(2.1) is generally pressurised (even when the
system is at a standstill). Before working on the
suction regulator this must be bled by carefully
unscrewing the return valve (2.3).
Standstill of the system
•
During plant standstill the suction regulator (-2)
should be closed via pressurisation in the lower
control area of the operating cylinder (-2.1-).
•
Solenoid valves (- 19 - (Y1) and - 20 - (Y4)) are
deenergised.
•
The oil separator vessel (-6-) is released via the
relief valve (-21-) to atmospheric pressure.
Starting the system
•
The motor starts up in the Y-mode.
•
The intake regulator is closed.
•
The compressor aspires a certain amount of air
through a bypass valve. Pressure builds up in the
reservoir.
•
The oil supply of the screw compressor takes place
through a drop in pressure between the oil separator
vessel and the injection spot in the screw
compressor.
•
When switching the drive motor over to
Δ
-mode,
switch the solenoid valves (-19-(Y1) and 20 (Y4) as
these are supplied with power.
•
The air circulated in the system streams over the
solenoid valve (-20- (Y4)) in the upper control area
of the operating cylinder (-2.1-). The relief valve
(-21-) is closed.
•
The lower control area of the operating cylinder
(-2.1-) is blocked and bled by the solenoid valve
(-19- (Y1)) from the oil separator vessel.
•
The pressure control valve (- 2.2 -) in the intake
regulator (- 2 -) opens.
•
At a reservoir pressure of approx. 4.5 bar/65 PSI the
pressure holding and check valve (- 15 -) opens.
•
Compressed air is now delivered into the consumer
network.
•
The system is now in load running mode.