Festo MPAC-VI, Руководство пользователя

Страница: 38 / 74

4 Commissioning
38 Festo – MPAC-VI-EN – 2017-12a – English
Immediately after switch-on, the pilot air supply must reach a pressure of 3 ... 8 bar. Otherwise there is
no guarantee that the valve will reverse directly (
è
Fig. 4.1).
If the pressure is less than 3 bar, there may be a delay before the valve is switched, in spite of an elec­
tric signal being present. The gradual pressure build-up of the overall supply does not affect the actuat­
or in that case. The actuator would react suddenly (e.g. a cylinder would extend or retract suddenly,
depending on the valve function).
1
4 2
5 3
14 12
1
12/14
12/14
3
82/84
2
1
2
1
External pilot air (3 to 8 bar), branched in
front of the safety start-up valve
2
Safety start-up valve (gradual pressure
build-up of the complete supply)
Fig. 4.1 Example: valve-cylinder combination with slow pressure build-up of the complete system
The table below shows the effects of gradual start-up pressurisation when electric signals are present:
External pilot air supply Pressure
rise in the
overall
supply
Pressure rise
in the pilot
air (12/14)
Time when a valve
reverses Movement
of the
actuator
Branched downstream of
the safety start-up valve
Slow
Slow
After
pressure rise at (1)
Fast
Branched upstream
of the safety start-up valve
Slow Fast Before pressure rise
at (1)
Slow
Tab. 4.1 Effects of slow start-up pressurisation