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5.14.2 Gas pressure
Indicates the pressure drop of the combustion head and the gas
butterfly valve depending on the operating output of the burner.
The values shown the table refer to:
–
natural gas G 20 NCV 10 kWh/Nm
–
natural gas G 25 NCV 8.6 kWh/Nm
Column 1
Combustion head pressure drop.
Gas pressure measured at test point 1)(Fig. 38), with:
•
combustion chamber at 0 mbar;
•
gas butterfly valve fully opened (90°) as in Fig. 38;
•
combustion head set as on page 22.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 38) 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. 38).
–
Find, in related to the burner concerned, the pressure value
closest to the result of the subtraction.
–
Read off the corresponding output on the left.
Example with G 20 natural gas:
Maximum output operation
Gas pressure at test point 1)(Fig. 38)
Pressure in combustion chamber
13.4 - 3.0
A pressure of 10.4 mbar, (column 1, corresponds in to an output
of 913 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. 38),
set the maximum modulating output required from the burner op-
eration:
–
find the nearest output value in for the burner in question.
–
Read, on the right (column 1), the pressure at the test point
1)(Fig. 38).
–
Add this value to the estimated pressure in combustion
chamber.
Example with G 20 natural gas:
Operation at maximum modulating output
Gas pressure at an output of 913 kW
Pressure in combustion chamber
10.4 + 3.0
pressure required at test point 1)(Fig. 38).
Installation
3
3
(8.6 Mcal/Nm
)
3
3
(7.4 Mcal/Nm
)
= 13.4 mbar
=
3.0 mbar
= 10.4 mbar
= 10.4 mbar
=
3.0 mbar
= 13.4 mbar
29
1 p (mbar)
kW
G20
290
1.7
394
2.5
498
3.5
601
4.8
705
6.4
809
8.2
913
10.4
1016
12.8
1120
15.5
1224
18.5
The heat output and gas pressure data in the
head refer to operation with gas butterfly valve
fully open (90°).
WARNING
WARNING
S9159
GB
2 p (mbar)
G25
G20
2.4
0.6
3.5
0.6
4.9
0.7
6.7
0.8
9.0
0.9
11.5
1.1
14.6
1.2
17.9
1.4
21.7
1.6
25.9
1.8
G25
0.8
0.8
1.0
1.1
1.3
1.5
1.7
2.0
2.2
2.5
Tab. O
Fig. 38
20168262
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