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4.12 Hydraulic connections
The pumps are equipped with a by-pass that connects return
line and suction line.
The pumps are installed on the burner with the by-pass closed
by screw 6)(Fig. 26). It is therefore necessary to connect both
hoses to the pump.
The pump will break immediately if it is run with
the return line closed and the by-pass screw in-
serted.
CAUTION
Remove the plugs from the suction and return connections of
the pump.
Insert the hose connections with the supplied seals into the
connections and screw them down.
Take care that the hoses are not stretched or twist-
ed during installation.
WARNING
Install the hoses where they cannot be stepped on or come
into contact with hot surfaces of the boiler and where they do
not hamper the opening of the burner.
Now connect the other end of the hoses to the suction and
return lines by using the supplied nipples.
4.12.1 Pressure variator
The pressure variator (Fig. 25) 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. 3 at page 11) which
simultaneously 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 pres-
sure on nozzle return.
The servomotor is operated by the electronic cam 11)(Fig. 4 at
page 12); 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. 3 at page 11) 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 regulating 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 sufficient.
Installation
1
Key (Fig. 25)
1 Nozzle pressure gauge
2 Position indicator (0 - 90) of pressure variator
31
GB
2
D9975
Fig. 25
20102963
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