■ 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 compressor block, the oil separa‐
tor tank and the control valve.
─ The pressure in the oil separator tank remains constant.
─ The engine runs at minimum speed.
■ STANDSTILL
─ The inlet valve closes.
─ The venting valve opens to depressurize the machine.
─ Machine cools down.
─ 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 volumetric flow rate within the machine's
regulating range, independent of the air demand.
With the help of an electrical control valve (the proportional controller), the opening and closing of
the inlet valve is continuously varied in response to the actual air demand. The airend provides
compressed air for connected consumers.
This continuous delivery regulation minimizes the fuel consumption of the engine. The load and
fuel consumption of the engine rises and falls with the air demand.
4.5 Safety devices
4.5.1 Monitoring functions with shut-down
The SIGMA CONTROL SMART monitors important machine parameters. The machine is automat‐
ically shut down if an alarm occurs.
The SIGMA CONTROL SMART saves the alarm message in its event memory.
Further information Further information on alarm messages at the controller is provided in chapter 9.2.1.
4.5.2 Further safety devices
The following safety devices are provided and may not be modified in any way:
■ «EMERGENCY STOP» push button
:«The EMERGENCY STOP» push button is for immediate shut-down of the machine. The mo‐
tor/engine comes to a stop. The pressure system is vented.
■ Safety relief valves:
Safety relief valves protect the system against unacceptable pressure rise. They are factory
set.
■ Enclosures and covers for moving parts and electrical connections:
Protect against unintentional contact.
4
Design and Function
4.5
Safety devices
42
Operator Manual Portable Rotary Screw Compressor
MOBILAIR M55 PE SIGMA CONTROL SMART pV
No.: 902366 10 USE
