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4.15.3 Gas pressure
Tab. J indicates the pressure drops of the combustion head and
gas butterfly valve, on the basis of the burner operating output.
The values shown in Tab. J refer to:
–
Natural gas G 20 NCV 9.45 kWh/Sm
–
Natural gas G 25 NCV 8.13 kWh/Sm
Column 1
Combustion head pressure drop.
Gas pressure measured at test point 1)(Fig. 25), with:
•
combustion chamber at 0 mbar;
•
burner working at maximum modulating output;
•
combustion head set as on page 17.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 25) with maximum
opening: 90°.
To calculate the approximate output at which the burner oper-
ates:
–
subtract the pressure in combustion chamber from the gas
pressure measured at test point 1)(Fig. 25).
–
Find, inTab. J related to the burner concerned, the pressure
value closest to the result of the subtraction.
Read the corresponding output on the left.
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at test point 1)(Fig. 25)
Pressure in combustion chamber
66.7 - 10
A pressure of 61.7 mbar (column 1) corresponds in Tab. J to an
output of 15500 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 1)(Fig. 25),
set the maximum modulating output required from the burner op-
eration:
–
find the nearest output value in Tab. J for the burner in ques-
tion.
–
read, on the right (column 1), the pressure at the test point
1)(Fig. 25).
–
Add this value to the estimated pressure in combustion
chamber.
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at an output of 15500 kW
Pressure in combustion chamber
61.7 + 5
pressure required at test point 1)(Fig. 25).
20155221
Installation
3
3
(8.2 Mcal/Sm
)
3
3
(7.0 Mcal/Sm
)
4.15.4 Pilot - gas train connection
The burner is fitted with a dedicated gas train that is fixed to the
pipe coupling.
It should be connected to the main train downstream the fil-
= 66.7 mbar
=
10 mbar
= 61.7 mbar
= 61.7 mbar
=
10 mbar
= 66.7 mbar
22
GB
1 p (mbar)
kW
G 20
3500
3.1
5000
6.4
6500
10.8
8000
16.5
9500
23.2
11000
31.1
12500
40.2
14000
50.4
15500
61.7
16500
70
The data of thermal output and combustion
head gas pressure are related to full open (90°)
gas butterfly valve.
WARNING
ter or the pressure adjuster (depending on configuration).
Supply pressure 68 ÷ 500 mbar.
WARNING
2 p (mbar)
G 25
G 20
G 25
4.6
0.4
0.6
9.5
0.8
1.2
16.1
1.5
2.1
24.4
2.2
3.2
34.5
3.1
4.5
46.2
4.2
6
59.6
5.5
7.8
74.8
6.8
9.8
91.7
8.4
12
104
9.5
13.6
Tab. J
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