13
20011755
GB
Hydraulic system
6.3
Depressurised systems
Depressurised systems (Fig. 11 and Fig. 12) have a negative fuel
pressure (depression) on intake to the burner. Usually the tank is
lower than the burner.
SYSTEM
ONLY FOR ITALY
:
Automatic shutoff device as per Ministry of Internal Affairs’ regu-
lation no. 73 dated 7/29/71.
H
= difference of level;
L
= max. length of the suction pipe;
ø
i
= internal diameter of the oil pipe.
In the systems in figs. 8 and 9, the table shows the maximum in-
dicated lengths for the supply line, depending on the difference in
level, length and the diameter of the oil pipes.
6.3.1
Pump priming
On the systems in Fig. 11 and Fig. 12 it is necessary to start the
burner and wait for the priming.
Should lockout occur prior to the arrival of the fuel, await at least
20 seconds before repeating the operation.
In two pipe vacuum systems (Fig. 13) the return line should ter-
minate within the oil tank at the same level as the suction line. In
this case a non-return valve is not required.
Should however the return line arrive over the fuel level, a non-
return valve is required.
This solution however is less safe than previous one, due to the
possibility of leakage of the valve.
WARNING
The installer must ensure that the supply de-
pression is not above 0.4 bar (30 cm Hg).
Above that level, gas leaks out from the fuel.
The pipes must all be perfectly sealed.
H
max. 4 m
H
D9345
ONE PIPE
Fig. 11
H
max
. 4 m
D9435
TWO PIPE
Fig. 12
H
meters
L meters
Øi
8 mm
Øi
10 mm
0
35
100
0,5
30
100
1
25
100
1.5
20
90
2
15
70
3
8
30
3.5
6
20
