KAESER M27 - 4.4 Operating modes and control modes

The air is then compressed in the airend 4 .
The airend is driven by an internal combustion engine 15 .
Cooling oil is injected into the airend. It lubricates moving parts and forms a seal between the ro‐
tors themselves and between them and the airend casing. This direct cooling in the compression
chamber ensures a very low airend discharge temperature.
Cooling oil recovered from the compressed air in the oil separator tank 5 gives up its heat in the oil
cooler 20 . The oil then flows through the oil filter 21 and back to the point of injection. Pressure
within the machine keeps the oil circulating. A separate pump is not necessary. A thermostatic
valve 19 maintains optimum cooling oil temperature.
Compressed air, freed of cooling oil in the oil separator tank 5 , flows through the minimum pres‐
sure nozzle 8 into the air distrubutor 10 . The minimum pressure nozzle ensures that there is al‐
ways sufficient internal air pressure to maintain cooling oil circulation.
The cooling fan 28 ensures optimum cooling of all components within the enclosure.
4.4 Operating modes and control modes
4.4.1 Operating modes
The machine operates in the following modes:
■
LOAD
─ The inlet valve is open.
─ The engine runs at maximum speed.
─ The airend delivers compressed air.
■ MODULATING
─ With the help of a control valve (the proportional controller) the degree of opening of the
inlet valve is continuously varied in response to the air demand.
─ This MODULATING control ensures minimum fuel consumption during times of low de‐
mand. The load and fuel consumption of the engine rises and falls with the air demand.
─ The airend delivers compressed air.
■ IDLE
─ The inlet valve is closed.
─ The control valve opens, allowing pressure in the oil separator tank to be applied to the inlet
valve.
─ Compressed air then flows in a closed circuit through the airend, the oil separator tank and
the control valve.
─ The pressure in the oil separator tank remains constant.
─ The engine runs at minimum speed.
■ STANDSTILL (shut down)
─ The inlet valve closes.
─ The venting valve opens to depressurize the machine.
─ The engine stops.
4.4.2 MODULATING control
The control system regulates the volume of air generated to match the actual demand. The ma‐
chine keeps the working pressure constant by varying the volume of compressed air delivered,
thereby matching the air demand.
4 Design and Function
4.4 Operating modes and control modes
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Operator Manual Screw Compressor
M27 No.: 9_9548 05 USE