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Appendix - Gas supply pressure
C
The table show minimum load losses along the gas supply line
depending on the maximum burner output operation.
The values shown in the tables refer to:
• Natural gas G 20 PCI 9.45 kWh/Sm
• Natural gas G 25 PCI 8.13 kWh/Sm
Column 1
Load loss at combustion head.
Gas pressure measured at the test point 1)(Fig. 39), with:
• Combustion chamber at 0 mbar;
• Burner working at maximum output;
• Combustion head adjusted according to the diagram of
Fig. 16.
Column 2
Load loss at gas butterfly valve 2)(Fig. 39) with maximum open-
ing: 90°.
NOTE
To know the approximate output at which the burner is operating
at its maximum:
- Subtract the combustion chamber pressure from the gas pres-
sure measured at test point 1)(Fig. 39).
- Find, in the table relating to the burner concerned, column 1,
the pressure value closest to the result you want.
- Read off the corresponding output on the left.
Example with natural gas G 20
• Maximum output operation
• Ring nut 2)(Fig. 15) adjusted as in the diagram of (Fig. 16)
• Gas pressure at test point 1)(Fig. 39)
• Pressure in combustion chamber
A pressure of 5.5 mbar, column 1, corresponds in the table to
an output of 900 kW.
This value serves as a rough guide; the effective output must
be measured at the gas meter.
NOTE
To know the required gas pressure at test point 1)(Fig. 39), set
the MAX output required from the burner operation:
- Find the nearest output value in the table for the burner in
question.
- Read, on the right, column 1, the socket pressure 1)(Fig.
39).
- Add this value to the estimated pressure in the combustion
chamber.
Example with natural gas G 20
• Required burner maximum output operation: 900 kW
• Ring nut 2)(Fig. 15) adjusted as in the diagram of (Fig. 16)
• Gas pressure at output of 900 kW
• Pressure in combustion chamber
pressure required at test point 1)(Fig. 39).
3
3
(8.2 Mcal/Sm
)
3
3
(7.0 Mcal/Sm
)
= 8 mbar
= 2.5 mbar
8 - 2.5
= 5.5 mbar
= 5.5 mbar
= 2.5 mbar
5.5 + 2.5
= 8 mbar
1 p (mbar)
kW
G 20
700
3,1
750
3,7
800
4,3
850
4,9
900
5,5
950
6,2
1000
6,8
1050
7,3
1100
7,9
1150
8,4
1200
9,1
1250
9,9
1300
10,8
1340
11,4
S8883
39
GB
2 p (mbar)
G 25
G 20
G 25
4,6
0,7
1,0
5,5
0,8
1,1
6,4
0,9
1,2
7,3
1,0
1,4
8,2
1,1
1,6
9,0
1,2
1,8
9,9
1,3
1,9
10,7
1,5
2,1
11,6
1,6
2,4
12,4
1,8
2,6
13,5
1,9
2,8
14,8
2,1
3,0
16,1
2,3
3,3
17,1
2,4
3,5
1
2
20133205
Fig. 39
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