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5.11.4 Gas pressure
Tab. N indicates the minimum pressure drops along the gas sup-
ply line, depending on the maximum burner output.
The values shown in Tab. N 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 the test point P1)(Fig. 27), with:
•
Combustion chamber at 0 mbar;
•
Burner working at maximum output;
•
Combustion head adjusted as in pag. 26.
Column 2
Pressure loss at gas butterfly valve 14)(Fig. 5 on pag. 14) 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. 27).
–
Find, in the table Tab. N related to the burner concerned, the
pressure value closest to the result of the subtraction.
–
read the corresponding output on the left.
Example RS 410/E MZ with G20 natural gas:
Maximum output operation
Gas pressure at test point P1)(Fig. 27)
Pressure in combustion chamber
A pressure of 41.7 mbar, column 1, corresponds in Tab. N to an
output of 4900 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. 27),
set the MAX output required from the burner operation:
–
find the nearest output value in the table Tab. N for the burner
in question.
–
read, on the right (column 1), the pressure at the test point
P1)(Fig. 27).
–
Add this value to the estimated pressure in the combustion
chamber.
Example RS 410/E MZ with G20 natural gas:
Required burner maximum output operation: 4900 kW
Gas pressure at an output of 4900
Pressure in combustion chamber
41.7 + 5
Pressure required at test point P1)(Fig. 27).
20079029
3
(8.2 Mcal/Sm
3
(7.0 Mcal/Sm
= 46.7 mbar
=
5 mbar
46.7 - 5
= 41.7 mbar
kW = 41.7 mbar
=
5 mbar
= 46.5 mbar
Installation
kW
1300
3
)
1560
3
)
1820
2080
2340
2600
2860
3120
3380
3640
3900
2000
2290
2580
2870
3160
3450
3740
4030
4320
4610
4900
2200
2540
2880
3220
3560
3900
4240
4580
4920
5260
5600
2400
2790
3180
3570
3960
4350
4740
5130
5520
5910
6300
GB
30
1 p (mbar)
2 p (mbar)
G 20
G 25
G 20
3.4
5.1
0.1
5.5
8.2
0.5
7.8
11.6
1.6
10.3
15.4
2.7
13.0
19.4
3.9
15.9
23.7
5.0
18.9
28.2
6.2
22.2
33.1
7.5
25.7
38.3
8.7
29.3
43.7
10.0
33.2
49.5
11.4
13.8
20.6
2.4
14.5
21.6
3.6
15.7
23.4
4.9
17.4
26.0
6.3
19.5
29.1
7.7
22.1
33.0
9.1
25.1
37.4
10.5
28.6
42.7
12.0
32.5
48.5
13.6
36.9
55.1
15.1
41.7
62.2
16.8
15.7
23.4
3.3
16.3
24.3
4.8
17.4
26.0
6.3
19.2
28.6
8.0
21.6
32.2
9.6
24.6
36.7
11.4
28.2
42.1
13.1
32.5
48.5
15.0
37.3
55.7
16.9
42.8
63.9
18.8
48.9
73.0
20.8
10.3
15.4
4.1
13.8
20.6
5.9
17.8
26.6
7.8
22.2
33.1
9.7
27.0
40.3
11.7
32.2
48.0
13.7
37.9
56.5
15.9
43.9
65.5
18.1
50.4
75.2
20.3
57.3
85.5
22.7
64.6
96.4
25.1
G 25
0.1
0.7
2.4
4.0
5.8
7.5
9.3
11.2
13.0
14.9
17.0
3.6
5.4
7.3
9.4
11.5
13.6
15.7
17.9
20.3
22.5
25.1
4.9
7.2
9.4
11.9
14.3
17.0
19.5
22.4
25.2
28.0
31.0
6.1
8.8
11.6
14.5
17.5
20.4
23.7
27.0
30.3
33.9
37.4
Tab. N
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