Two-Pipe System; 5.11.1 Priming Pump - Riello RDB 3.2 BX 32/50 Installation, Use And Maintenance Instructions

5.11

Two-pipe system

Two-pipe vacuum systems (Fig. 13) have a negative fuel pres-
sure (depression) on the burner intake.
Usually the tank is lower than the burner.
The return line should terminate in 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 arrives over the fuel level, the
non-return valve is indispensable. This solution however is less
safe than previous one, due to the possibility of leakage of the
valve.
You are advised to use additional filters on the fuel
supply line.
The manufacturer recommends the use of a good
CAUTION
quality fuel filter on the tank (Fig. 13), and a sec-
ondary filter (60 m for light oil and 15 m for kero-
sene), to protect the burner pump and nozzle from
contamination.
In case of biodiesel use, pay attention to install
bio-compatible filters.

5.11.1 Priming pump

Before starting the burner make sure that the re-
turn pipe-line is not clogged: any obstruction
would cause the pump seals to break.
WARNING
On the system in Fig. 13, 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.
The pump vacuum should not exceed a maximum
of 0.4 bar (30 cm Hg).
Beyond this limit gas is released from the oil.
WARNING
Installation
H
metres
0
0.5
1
1.5
2
3
3.5
H difference of level
L max. length of the suction line
I.D. internal diameter of the oil pipes
NOTE:
The Tab. C shows the maximum approximate lengths for the sup-
ply line, depending on the difference in level, length, and the di-
ameter of the fuel conduit.
17
GB
D10011
L metres
I.D. (8 mm)
35
30
25
20
15
8
6
Fig. 13
I.D. (10 mm)
100
100
100
90
70
30
20
Tab. C
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