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5.13.4 Gas pressure
indicates the minimum pressure drops along the gas supply line,
depending on the maximum burner output.
The values shown in refer to:
–
Natural gas G 20 NCV 9.45 kWh/Sm
Column 1
Pressure drop on combustion head.
Gas pressure measured at the test point P1)(Fig. 28 on page 28),
with:
•
Combustion chamber at 0 mbar;
•
Burner working at maximum output;
•
Combustion head adjusted as in page 22.
Column 2
Pressure loss at gas butterfly valve 29)(Fig. 4 on page 11) with
maximum opening: 90°.
Calculate the approximate maximum output of the burner in this
way:
–
subtract the combustion chamber pressure from the gas
pressure measured at test point P1)(Fig. 28 on page 28).
–
Find, in the table related to the burner concerned, the pres-
sure value closest to the result of the subtraction.
–
read the corresponding output on the left.
Example with G20 natural gas:
Maximum output operation
Gas pressure at test point P1)(Fig. 28 on
page 28)
Pressure in combustion chamber
A pressure of 13.2 mbar, column 1, corresponds in the table to
an output of 3000 kW.
This value serves as a rough guide; the effective output must be
measured at the gas meter.
To calculate the required gas pressure at test point P1)(Fig. 28
on page 28), set the MAX output required from the burner opera-
tion:
–
find the nearest output value in the table for the burner in
question.
–
read, on the right (column 1), the pressure at the test point
P1)(Fig. 28 on page 28).
–
Add this value to the estimated pressure in the combustion
chamber.
Example with G20 natural gas:
Required burner maximum output operation: 3000 kW
Gas pressure at an output of 3000 kW
Pressure in combustion chamber
Pressure required at test point P1)(Fig. 28 on page 28).
Installation
3
3
(8.2 Mcal/Sm
)
=
15.2 mbar
=
2 mbar
15.2 - 2 =
13.2 mbar
=
13.2 mbar
=
2 mbar
13.2 + 2 =
15.2 mbar
29
kW
5400
5000
4000
3000
2000
1080
0% Flue gas recirculation
The data of thermal output and combustion
head gas pressure are related to full open (90°)
gas butterfly valve.
WARNING
GB
1 p (mbar)
1 p (mbar)
G 20
G 20
43.0
1.1
36.8
--
23.5
--
13.2
--
5.8
--
1.7
--
Tab. Q
20171988
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