Burner Firing Rates According To Air Density - Riello RLS 28 Installation, Use And Maintenance Instructions

7.4

Burner firing rates according to air density

average barom.
above sea level
pressure
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
"w.c.
H2
H3
H1
D2617
The FIRING RATE area values have been obtained considering a
surrounding temperature of 68°F (20°C), and an atmospheric pres-
sure of 398" W.C. and with the combustion head adjusted as
shown on page 14.
The burner may be required to operate with combustion 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.
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 al-
titude conditions. Proceed as follows to check the above:
1 - Find the correction factor F in the Tab. K for the plant's air tem-
perature and altitude.
2 - Divide the burner's delivery Q by F in order to obtain the equiv-
alent delivery Qe:
Qe = Q : F (MBTU/h)
3 - In the firing rate range of the burner, (Fig. 34), indicate the work
point defined by:
Qe = equivalent delivery
H1 = combustion chamber pressure
The resulting point A must remain within the firing rate range.
C6505058 - 2915759
Electrical system
mbar 0 (0°C) 41 (5°C)
1013 1,087 1,068
1000 1,073 1,054
989 1,061 1,042
978 1,050 1,031
966 1,037 1,018
955 1,025 1,007
944 1,013 0,995
932 1,000 0,982
921 0,988 0,971
910 0,977 0,959
898 0,964 0,946
878 0,942 0,925
856 0,919 0,902
836 0,897 0,881
815 0,875 0,859
794 0,852 0,837
A
MBtu/hr
Qe
Fig. 34
CORRECTION FACTOR F
Air temperature
°F (°C)
50 (10°C) 59 (15°C) 68 (20°C)
1,049 1,031 1,013
1,035 1,017 1,000
1,024 1,006 0,989
1,013 0,995 0,978
1,000 0,983 0,966
0,989 0,972 0,955
0,977 0,960 0,944
0,965 0,948 0,932
0,954 0,937 0,921
0,942 0,926 0,910
0,930 0,914 0,898
0,909 0,893 0,878
0,886 0,871 0,856
0,866 0,851 0,836
0,844 0,829 0,815
0,822 0,808 0,794
4 - Plot a vertical line from Point A as shown in (Fig. 34) 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. 34), the burner delivers
the output required.
If H3 is lower than H1, the burner's delivery must be reduced. A re-
duction 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
H1r = H1 x (0.95)2
Steps 2 - 5 must now be repeated using the new Qr and H1r values.
NOTE:
the combustion head must be adjusted in respect to the equiv-
alent delivery Qe.
34
77 (25°C) 86 (30°C)
0,996 0,980
0,983 0,967
0,972 0,956
0,962 0,946
0,950 0,934
0,939 0,923
0,928 0,913
0,916 0,901
0,906 0,891
0,895 0,880
0,883 0,868
0,863 0,849
0,842 0,828
0,822 0,808
0,801 0,788
0,781 0,768
(" W.C.)
104 (40°C)
0,948
0,936
0,926
0,916
0,904
0,894
0,884
0,872
0,862
0,852
0,841
0,822
0,801
0,783
0,763
0,743
Tab. K