5
GAS PRESSURE
The adjacent table shows minimum pressure
losses along the gas supply line depending on
the burner output in 2nd stage operation.
Column 1
Pressure loss at combustion head.
Gas pressure measured at test point 1)(B), with:
• Combustion chamber at 0 mbar
• Burner operating in 2nd stage
• Combustion head adjusted as indicated in
diagram (C)p. 7.
Column 2
Pressure loss at gas butterfly valve 2)(B) with
maximum opening: 90°.
Column 3
Pressure loss of gas train 3)(B) includes: adjust-
ment valve VR, safety valve VS (both fully
open), pressure governor R, filter F.
The values shown in the table refer to:
natural gas G 20 NCV 9.45 kWh/Sm3
(8,2 Mcal/Sm3)
With:
natural gas G 25 NCV 8,13 kWh/Sm3
(7,0 Mcal/Sm3) multiply tabulated values:
- column 1 - 2: by 1.5
- column 3: by 1.35.
Calculate the approximate 2nd stage output of
the burner thus:
- Subtract the combustion chamber pressure
from the gas pressure measured at test point
1)(B).
- Find the nearest pressure value to your result
in column 1 of the table (A).
- Read off the corresponding output on the left.
Example:
• 2nd stage operation
• Natural gas G 20 NCV 9.45 kWh/Sm3
• Gas pressure at test point 1)(B) = 11 mbar
• Pressure in combustion chamber = 3 mbar
11 - 3= 8 mbar
A 2nd stage output of 1600 kW shown in Table
(A) corresponds to 8 mbar pressure, column 1.
This value serves as a rough guide, the effective
delivery must be measured at the gas meter.
To calculate the required gas pressure at test
point 1)(B), set the output required from the
burner in 2nd stage operation:
- Find the nearest output value in the table (A).
- Read off the pressure at test point 1)(B) on
the right in column 1.
- Add this value to the estimated pressure in
the combustion chamber.
Example:
• Required burner output in 2nd stage opera-
tion: 1600 kW
• Natural gas G 20 NCV 9.45 kWh/Sm3
• Gas pressure at burner output of 1600 kW,
taken from table (A), column 1 = 8 mbar
• Pressure in combustion chamber = 3 mbar
8 + 3 = 11 mbar
pressure required at test point 1)(B).
(A)
RS 190 p (mbar)
kW 1 2
3
3970181
3970182
3970221
3970225
3970222
3970226
3970223
3970227
1280 7.0 1.3 28.6 10.3 7.2 4.8
1400 7.3 1.6 33.5 12.1 8.2 5.2
1500 7.6 1.8 37.7 13.6 9.0 5.5
1600 8.0 2.1 41.8 15.2 9.9 5.8
1700 8.7 2.4 46.0 16.7 10.7 6.1
1800 9.3 2.7 50.2 18.2 11.6 6.5
1900 10.2 3.0 54.3 19.8 12.5 6.8
2000 11.3 3.3 59.3 21.6 13.6 7.3
2100 12.5 3.6 64.4 23.5 14.8 7.7
2290 15.0 4.3 74.1 27.1 17.0 8.6
(B)
D3734
MB 420
MBC 1200
MBC 1900
MBC 3100
