Burner Firing Rates According To Air Density - Riello PRESS GW Installation, Use And Maintenance Instructions

4.6.1

Burner firing rates according to air density

The burner firing rate range provided in this Manual applies to op-
eration at a surrounding temperature of 20°C at an altitude of 100
meters above sea level (atmospheric pressure approx. 1000
mbar).
The burner may be required to operate with comburent air at a
higher temperature and/or at higher altitudes.
Heating of air and increase in altitude produce the same effect:
the expansion of the air volume, i.e. the reduction of air density.
Altitude
(1)
a.s.l.
m mbar
0 1013
100 1000
200 989
300 978
400 966
500 955
600 944
700 932
800 921
900 910
1000 898
1200 878
1400 856
1600 836
1800 815
2000 794
(1)AVERAGE BAROM. PRESS.
2 -Divide the burner's delivery Q by F in order to obtain the equiv-
alent delivery Qe:
Qe = Q : F
3 -In the firing rate range of the burner (Fig. 4), 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 (Fig. 4) 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.
H3 = H2 x F
If H3 is greater than "H1", as shown in (Fig. 4), the burner deliver
the output required.
If H3 is lower than H1, the burner's delivery must be reduced.
Technical description of the burner
0 5
1,087 1,068 1,049
1,073 1,054 1,035
1,061 1,042 1,024
1,050 1,031 1,013
1,037 1,018 1,000
1,025 1,007 0,989
1,013 0,995 0,977
1,000 0,982 0,965
0,988 0,971 0,954
0,977 0,959 0,942
0,964 0,946 0,930
0,942 0,925 0,909
0,919 0,902 0,886
0,897 0,881 0,866
0,875 0,859 0,844
0,852 0,837 0,822
(kg/h)
(mbar)
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 conditions. Proceed as follows to check the above:
1 -Find the correction factor F in the Tab. D for the plant's air tem-
perature and altitude.
Correction factor F
Air temperature °C
10 15 20
1,031 1,013
1,017 1,000
1,006 0,989
0,995 0,978
0,983 0,966
0,972 0,955
0,960 0,944
0,948 0,932
0,937 0,921
0,926 0,910
0,914 0,898
0,893 0,878
0,871 0,856
0,851 0,836
0,829 0,815
0,808 0,794
mbar
D388
A reduction in delivery is accompanied by a reduction of the pres-
sure in the combustion chamber:
Qr = reduced delivery
H1r = reduced pressure
2
H = H x (Qr/Q)
1r 1
Example, a 5% delivery reduction:
Qr = Q x 0,95
2
H = H x (0,95)
1r 1
Steps 2-5 must now be repeated using the new Qr and H
ues.
The combustion head must be adjusted in respect
to the equivalent delivery Qe.
CAUTION
11 GB
25 30
0,996 0,980 0,948
0,983 0,967 0,936
0,972 0,956 0,926
0,962 0,946 0,916
0,950 0,934 0,904
0,939 0,923 0,894
0,928 0,913 0,884
0,916 0,901 0,872
0,906 0,891 0,862
0,895 0,880 0,852
0,883 0,868 0,841
0,863 0,849 0,822
0,842 0,828 0,801
0,822 0,808 0,783
0,801 0,788 0,763
0,781 0,768 0,743
Qe
40
Tab. D
kg/h
Fig. 4
val-
1r
20140894