20102152
8
GB
Technical description of the burner
3.7
Firing rate
The
maximum output
is chosen within area A) and B)(Fig. 3) of
the diagram.
The
minimum output
must not be lower than the minimum limit of
the diagram.
3.7.1
Procedure to refer burner operating condition
in high altitude plants
Find the
CORRECTED BURNER CAPACITY
for the plant’s alti-
tude in chart
1
and the
CORRECTED PRESSURE
in chart
2
.
Check in the firing rate graph of the burner (Fig. 3), 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 tem-
perature = 68°F, 20°C)
To get the combined correction in case of different air tem-
perature, a compensation of 1000 ft each 3.6°F (305 m each
2°C) is applicable (100 ft = 0.36°F).
Example
–
Rated Capacity = 2517 MBtu/hr
–
Rated Air Pressure = 1.39” WC
–
Reference Altitude = 328 ft
–
Reference Temperature = 20°C = 68°F
–
Real Altitude = 3000 ft
–
Real Temperature = 17°C = 62.6°F
–
Temperature Difference = 68°F - 62.6°F = 5.4°F
–
Virtual Altitude Increment = 5.4°F/3.6°F x 1000 ft = 1500 ft
–
Virtual Altitude = (Real Altitude) + (Virtual Altitude Increment) =
3000 ft + 1500 ft = 4500 ft
–
Corrected Capacity = (2585 + 2607)/2 = 2596 MBtu/hr
–
Corrected Pressure = (2.76 + 3.19)/2 = 2.98” WC
Reference conditions:
–
Ambient Temperature 68 °F (20 °C)
–
Barometric Pressure 394” WC (1000 mbar)
–
Altitude 328 ft a.s.l. (100 m a.s.l.)
WARNING
To use area B) as well, the pre-calibration of the
combustion head is necessary, as explained in the
paragraph
"Pre-calibration of combustion head"
WARNING
The firing rate was obtained considering a room
temperature of 68 °F and an atmospheric pressure
of 394 “WC (approx. 0 ft above sea level), with the
combustion head adjusted.
Fig. 3
20061167
Pressure in com
b
ustion
chamber -
“WC
Thermal power
