Oil Circuit; Air Circuit; System Control; System Control L15-L22 - Gardner Denver L15 Original Operating Manual

5. Design and functioning
5.3

Oil circuit

The oil flows from the pressure reservoir (- 6 - Fig. 3)
into the oil thermostat (- 17 - Fig. 3). With oil tempera-
tures < 131 °F the oil flows via the by-pass of the oil
cooler directly into the oil filter (- 11 - Fig. 3) and is then
injected into the screw compressor (- 4 - Fig. 3).
With oil temperatures of between 131 °F and 158 °F the
oil flow is divided and fed into the oil cooler (-12- Fig. 3)
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 - Fig. 3) 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 suction regulator (- 2 - Fig. 3) is
closed, a vacuum pressure occurs in the intake
connection.
Excess pressure of approx. 22 PSI is produced in the
pressure reservoir at the same time.
5.4

Air circuit

The intake air passes through the intake filter (- 1 - Fig. 3)
and the suction regulator (- 2 - Fig. 3) into the screw
compressor (- 4 - Fig. 3). During the compression
process, the intake air is cooled via the injected oil, and
the developed air/oil mixture flows tangentially into the
pressure reservoir (oil reservoir) (- 6 - Fig. 3). After pre-
separation and subsequent fine separation by the
separator element (- 7 - Fig. 3), the compressed air with
a low oil content is fed via the minimum pressure valve
(- 15 - Fig. 3) and the air cooler (- 16 - Fig. 3) into the
consumer network.
20
5.5

System control

Fig. 4

5.5.1 System control L15-L22

Standstill of the system
When the system is at rest the suction regulator
•
(- 2 - Fig. 4) is closed.
The solenoid valve (Y1 Fig. 4) is de-energized.
•
The pressure reservoir (- 5 - Fig. 4) is bled via the
•
blow-off line (- 2.2 - Fig. 4) and the orifice (-9- Fig. 4)
into the suction channel.
Starting the system
The motor (- 3 - Fig. 4) starts up in the Y-mode.
•
The compressor extracts a certain volume of air via
•
a start valve (- 2.1 - Fig. 4). Pressure builds up in
the reservoir and closes the regulator.
When changing over to Δ operation, the solenoid
•
valve (- Y1 - Fig. 4) is energized, which blocks the
connection between pressure vessel and suction
regulator.
The suction regulator opens due to the intake
•
vacuum pressure. Venting of the control piston
takes place via the blow-off line.
The minimum pressure valve (- 8 - Fig. 4) opens
•
when the pressure reservoir is approx. 65 PSI.
Compressed air is now delivered into the consumer
•
network.