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7.6
Combustion head
The combustion head comprises a highly heat resistant cylinder
whose surface features numerous holes, encased in a metal
"mesh".
The air-gas mixture is pushed inside the cylinder and out of the
head through the holes in the perimeter.
Pilot system operates correctly with pressure between 5 and
20 mbar. Such value can be varied by means of pressure regula-
tor 3)(Fig. 163 on page 49).
Combustion begins with ignition of the air/gas mixture that comes
out of the pilot system by means of the electrode spark.
After the stabilization of the pilot flame (approx. 3 seconds), the
main valve opens up and, after approx. 7 seconds, the pilot flame
goes out while the main one stays on.
The metal "mesh" is the combustion head's most essential ele-
ment since it improves burner performance considerably.
The flame developed on the surface of the head is perfectly re-
tained and adheres to the mesh when operating at the maximum
setting.
This allows modulating ratios as high as 6:1, avoiding the danger
of flashback when modulating is at its minimum.
The flame features an extremely compact geometry, meaning
that there is no risk of contact between the flame and parts of the
generator, consequently eliminating the possible problem of poor
combustion.
The flame's structure means that smaller combustion chambers
can be developed, designed to exploit this particular feature.
Before starting up the burner, it is good practice to
adjust the gas train so that ignition takes place in
conditions of maximum safety, i.e. with gas deliv-
ery at the minimum.
CAUTION
Start-up, calibration and operation of the burner
53
GB
20152192
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