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5.12.4 Pressure regulator
The pressure variator (Fig. 20), integrated into the valve unit of
the oil circuit makes it possible to vary the pressure on return of
the nozzle depending on the flow rate required.
Governing of the pressure on return is obtained with the variation
of a section by rotating the servomotor 23)(Fig. 4) which simulta-
neously also controls the gas butterfly valve.
Pressure governor at 0° (maximum opening) minimum pres-
sure on nozzle return.
Pressure governor at 90° (minimum opening) = maximum
pressure on nozzle return.
The servomotor is operated by the electronic cam 4)(Fig. 5); by
means of this device it is possible to set different curves for oil
and gas on the same servomotor (the air gate valve servomotor
4)(Fig. 4) may be operated in the same way.
In adjusting with gas it is advisable to set the servomotor at
90° in order to reduce losses from the gas butterfly valve.
In adjusting with oil , setting is made depending on the type
of nozzle used and on the modulation required. Under the
conditions of minimum firing rate, 20° rotation may be suffi-
cient.
D3520
Key to layout (Fig. 20)
1
Nozzle delivery pressure gauge
2
Pressure gauge for pressure on nozzle return
3
Position indicator (0 ÷ 90) of pressure variator
4
Maximum oil pressure switch on return circuit
20010309
Installation
5.12.5 Hydraulic system layout
Key to layout (Fig. 21)
1
Pump suction
2
Pump and nozzle return
3
By-pass screw in pump
4
Pump pressure governor
5
Safety solenoid
6
Safety solenoid
7
Nozzle delivery
8
Nozzle without interception pin
9
Nozzle return
10 Pressure variator on nozzle return
11 Servomotor for pressure variator
12 Pressure switch on nozzle return
13 Safety valve on nozzle return
14 Safety valve on nozzle return
15 Pressure switch on pump delivery
Fig. 20
B
Oil valve assembly and pressure variator
M Pressure gauge
V
Vacuometer
OPERATION
Pre-purging phase:
of closed valves 5), 6), 13) and 14).
Firing phase and operation:
of opened valves 5), 6), 13) and 14).
Halt : All the valves closed.
22
GB
D3517
Fig. 21
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