Technical description of the burner
9
20045163
GB
3.9
Firing rate
During operation, burner output varies between:
– MINIMUM OUTPUT: area A;
– MAXIMUM OUTPUT: area B.
NOTE:
The firing rate areas given in Fig. 5 have been reduced by 10%
with respect to the maximum range that can be reached.
The firing rate (Fig. 5) may be found by plotting a vertical line from
the desired delivery and a horizontal line from the pressure in the
combustion chamber.
The intersection of these two lines is the firing rate which must lie
within area A, for MIN output, and within area B, for MAX output.
Consult Procedure on page 9 to refer burner operating condition in
high altitude plants.
3.9.1
Procedure to refer burner operating condition
in high altitude plants
Find the corrected burner capacity for the plant’s altitude in chart
1 and the corrected pressure in chart 2.
Check in the firing rate graph of the burner (Fig. 5), if the working
point defined by the values above is within the range limits.
If not, higher burner size is needed.
Note
Charts are based only on altitude variation (reference temperature
= 68°F , 20°C)
To get the combined correction in case of different air temperature,
a compensation of 1000 ft each 20°F (305 m each 11°C) is appli-
cable.
Example
Rated capacity = 3000 MBtu/hr - Rated air pressure = 1.5”WC.
Real altitude = 5000 ft - Real temperature = 108°F
∆
= 108°F - 68°F (reference temp.) = 40°F (equivalent 2000 ft var-
iation)
Proceeding as descripted above and considering a “virtual altitude”
of (5000 + 2000) ft:
- the corrected capacity is 3847 MBtu/hr
- the corrected burner air pressure is 1.92
Reference conditions (Charts 1-2):
– Ambient temperature 68 °F (20 °C)
– Barometric pressure 394” WC (1000 mbar)
– Altitude 328 ft a.s.l. (100 m a.s.l.).
WARNING
The firing rate area values have been obtained con-
sidering an ambient temperature of 68 °F (20°C),
and an atmospheric pressure of 394” WC and with
the combustion head adjusted as shown on
page 17.
Fig. 5
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D12158
Burner output
