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APPENDIX
- Burner firing rates according to air density
average barom.
above sea level
ft
m
" W.C.
0
0
399
329
100
394
658
200
389
987
300
385
1316
400
380
1645
500
376
1974
600
372
2303
700
367
2632
800
363
2961
900
358
3290
1000
354
3947
1200
346
4605
1400
337
5263
1600
329
5921
1800
321
6579
2000
313
(A)
The FIRING RATE area values have been obtained considering a surround-
ing temperature of 68°F (20°C), and an atmospheric pressure of 398" W.C.
and with the combustion head adjusted as shown on page 7.
The burner may be required to operate with combustion air at a higher tem-
perature and/or at higher altitudes.
Heating of air and increase in altitude produce the same effect: the expan-
sion of the air volume, i.e. the reduction of air density.
The burner fan's delivery remains substantially the same, but the oxygen
content per cubic meter and the fan's head are reduced.
It is therefore important to know if the maximum output required of the burner
at a given combustion chamber pressure remains within the burner's firing rate range even at different temperature and altitude con-
ditions. Proceed as follows to check the above:
1 -Find the correction factor F in the Table (A) for the plant's air temperature and altitude.
2 -Divide the burner's delivery Q by F in order to obtain the equivalent delivery Qe:
Qe = Q : F (MBtu/hr)
3 -In the firing rate range of the burner, Fig. (B), indicate the work point defined by:
Qe = equivalent delivery
H1 = combustion chamber pressure
The resulting point A must remain within the firing rate range.
4 -Plot a vertical line from Point A as shown in Figure (B) and find the maximum pressure H2 of the firing rate.
5 -Multiply H2 by F to obtain the maximum reduced pressure H3 of the firing rate.
H
= H
x F (" W.C.)
3
2
If H3 is greater than H1, as shown in Fig. (B), the burner delivers the output required.
If H3 is lower than H1, the burner's delivery must be reduced. A reduction in delivery is accompanied by a reduction of the pressure in
the combustion chamber:
Qr = reduced delivery
H1r = reduced pressure
Qr
2
( )
H
r = H
x
1
1
Q
Example, a 5% delivery reduction:
Qr = Q x 0.95
2
H1r = H1 x (0.95)
Steps 2 - 5 must now be repeated using the new Qr and H1r values.
Important: the combustion head must be adjusted in respect to the equivalent delivery Qe.
pressure
mbar
0 (0°C)
1013
1,087
1000
1,073
989
1,061
978
1,050
966
1,037
955
1,025
944
1,013
932
1,000
921
0,988
910
0,977
898
0,964
878
0,942
856
0,919
836
0,897
815
0,875
794
0,852
CORRECTION FACTOR
Air temperature
41 (5°C)
50 (10°C)
59 (15°C)
1,068
1,049
1,031
1,054
1,035
1,017
1,042
1,024
1,006
1,013
0,995
1,031
1,018
1,000
0,983
0,972
1,007
0,989
0,995
0,977
0,960
0,982
0,965
0,948
0,971
0,954
0,937
0,959
0,942
0,926
0,946
0,930
0,914
0,925
0,909
0,893
0,902
0,886
0,871
0,881
0,866
0,851
0,859
0,844
0,829
0,837
0,822
0,808
" W.C.
H
2
H
3
H
1
16
F
°F (°C)
68 (20°C)
77 (25°C)
86 (30°C)
1,013
0,996
1,000
0,983
0,989
0,972
0,978
0,962
0,966
0,950
0,955
0,939
0,944
0,928
0,932
0,916
0,921
0,906
0,910
0,895
0,898
0,883
0,863
0,878
0,856
0,842
0,836
0,822
0,815
0,801
0,794
0,781
A
Qe
104 (40°F)
0,980
0,948
0,967
0,936
0,956
0,926
0,946
0,916
0,934
0,904
0,923
0,894
0,913
0,884
0,901
0,872
0,891
0,862
0,880
0,852
0,868
0,841
0,849
0,822
0,828
0,801
0,808
0,783
0,788
0,763
0,743
0,768
MBTU/h
(B)
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