Oil Circuit; Air Circuit; System Control - Gardner Denver L Series Original User And Service Manual

5.3

Oil circuit

The oil flows from the pressure reservoir (- 6 -) into the
oil thermostat (- 16 -). With oil temperatures < 131 °F
the oil flows via the by-pass of the oil cooler directly into
the oil filter (- 17 -) 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 (- 15 -) 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 (- 7 -) is
fed through an oil scavage 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.
5.4

Air circuit

The intake air passes through the intake filter (- 1 -) and
the intake regulator (- 2 -) into the screw compressor
(- 4 -). 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) (- 6 -). After pre-separation and subsequent
fine separation by the separator element (- 7 -), the
compressed air with a low oil content is fed via the
minimum pressure valve (- 12 -) and the air cooler
(- 14 -) into the consumer network.
5.5

System control

(See also operating instructions for the compressor
controller)
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 (- 23 - (Y1)) is de-energized.

The oil separator vessel is released via valve
(- 24 -) to atmospheric pressure.

The cooling water solenoid valve (-33-(Y6)) is
closed in a de-energized state (only water-cooled
units)
Starting the system

The motor starts up in the Y-mode.

The cooling water solenoid valve (-33-(Y6)) is
supplied with power and opens (only water-cooled
units).

The intake regulator is closed.

The compressor aspires a certain amount of air
through an adjustable choke valve (bypass valve)
(- 2.4 -). Pressure builds up in the pressure vessel.

The oil supply of the screw compressor takes place
through a drop in pressure between the pressure
vessel and the injection spot in the screw
compressor.

If the drive motor is switched over to Δ operation,
the magnetic valve switches over (-23-(Y1) since it
is supplied with current.

The air circulated in the system streams over the
solenoid valve (-23- (Y1)) in the upper control area
of the operating cylinder (-2.1-). The blow off valve
(-24-) is closed. The lower control space of the
adjusting cylinder is ventilated.

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 (- 12 -) opens.

Compressed air is now delivered into the consumer
network.

The system is now in load running mode.
13-25-639 v00 Page 22