Oil Circuit; Air Circuit; System Control; Manner Of Operation Of The Suction Regulator - Gardner Denver L Series Service Manual

Oil circuit

5.3
The oil flows from the pressure reservoir (-22-) into the
oil thermostat (-13-). With oil temperatures < 131°F the
oil flows via the by-pass of the oil cooler directly into the
oil filter (-12-) and is then injected into the screw
compressor (-4-).
With oil temperatures of between 131°F and 158°F the
oil flow is divided and fed into the oil cooler (-14-) and
the by-pass.
With oil temperatures above 158°F the entire oil flow is
directed via the oil cooler through the oil filter into the
screw compressor.
The oil separated by the oil separator element (-27-) is
fed through an oil scavenge line to the screw
compressor.
The entire oil circulation is based on a differential
pressure in the system. Considering the pressure
difference of approx. 29 PSI within the oil circuit, the oil
is then injected into the screw compressor with approx.
116 PSI at a reservoir pressure of e.g. 145 PSI.
When the screw compressor is in the off-load mode, a
sufficiently high pressure differential and thus the
required oil injection quantity is achieved owing to the
fact that when the intake regulator (-2-) is closed, a
vacuum pressure occurs in the intake connection and at
the place of injection.
Excess pressure of approx. 22 PSI (off-load pressure)
is produced in the pressure reservoir at the same time.

Air circuit

5.4
The intake air passes through the intake filter (-1-) and
the intake regulator (-2-) into the screw compressor
(-7-). During the compression process, the intake air is
cooled via the injected oil. The developed air/oil mixture
flows tangentially into the pressure reservoir (oil
reservoir) (-22-). After pre-separation and subsequent
fine separation by the separator element (-27-), the
compressed air with a low oil content is fed via the
minimum pressure valve (-28-) and the air cooler
(-30-) into the consumer network.

System control

5.5
(See also operating instructions for the compressor
controller)
5.5.1 System control L55-75
Standstill of the system

If the plant is shut down, the suction controller (-2-)
is closed by a pressure spring at the adjusting
cylinder (-2.1-).

The solenoid valve (-5-(Y1)) is de-energized.

The oil separator vessel is released via valve
(-4-) to atmospheric pressure.
Starting the system

The drive motor (-9-) starts up in the Y-mode.

The cooling water solenoid valve (-34-(Y6)) is
supplied with power and opens (only water-cooled
units).

The intake regulator (-2-) is closed.

The compressor aspires a certain amount of air
through bypass line with check valve Pressure
builds up in the pressure vessel.

Oil is supplied to the screw compressor (-7-)
due to the pressure differential between the
pressure reservoir (-22-) and the place of
injection in the screw compressor (-7-).

When the drive motor (-9-) switches to Δ
operation, solenoid valves (-5- (Y1) and -4-
(Y4)) perform a switching operation, since they
are energized.

The control chamber of the actuator (-2.2-) is
isolated from the pressure vessel (-22-) by the
solenoid valve (-5- (Y1)) and is bled into the
intake channel.

The choke valve (-2.2-) in the intake regulator
(-2-) opens.

At a reservoir pressure of approx. 65 PSI the
pressure holding and check valve (-28-) opens.

Compressed air is now delivered into the consumer
network.

The system is now in load running mode.
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