North American Dual-Fuel ™ Hot Spot Burners Sheet 6841 Dual-Fuel ™ Hot Spot Burners produce short, intense, concentrated flames on gas or distillate oil. Two sizes are available -- 6841-7, which uses 20 osi atomizing air, and 6841-8-B25, which uses 15 psi compressed air for atomization. Excellent turndown characteristics of the 6841-8-B25 permits its use over the capacity range normally served by -8-A and -8-B burners. Use of atomizing air during gas operation permits equal capacity on gas or oil. If reduced gas capacity is acceptable for the 6841-8-B25, compressed air can be reduced to 1 psig (minimum to prevent atomizer overheating). The 6841-7 is stable in a cold, tight chamber. Do not run it rich on oil.
6841-7 Burners have 13 ½ " square by 9" (nominal) long tiles. 6841-8-B25 Burners have 24" diameter grooved tiles. Tiles are of refractory material suitable for 3000°F tile temperature. Tile cover plates are heat-resisting cast iron. Burner internals that see flame are alloy.
Required gas pressure at the burner connection is 3 osi for 6841-7 and 1.5 osi for 6841-8-B25.
Pilots, Flame Supervision. A 4011-12 pilot set is recommended for individual burner ignition. When multiple burners share a single pilot pre-mix header, a 4021-12 pilot tip per burner with an appropriately sized air/gas mixer is recommended. Pilot Tips use 6"wc mixture pressure. Flame rods or UV detectors work satisfactorily with pilot and main gas flames. For monitoring oil fires, only UV is satisfactory--flame rods tend to collect carbon. For satisfactory operation, UV detectors must be purged with air. Flame detectors must be installed clockwise of pilot as viewed from rear of burner. Total Capacities. Gas capacity is based on 0.6 sp gr, 1000 Btu/ft 3 gas, using main and full atomizing air. Oil capacity is based on #2 oil at 140 000 Btu/gallon.
16 osi main air pressure drop acrosss burner
12 osi main air pressure drop across burner
Burner designation
Air, scfh 22 100 57 600
Gas, scfh
Oil, gph
Air, scfh Gas, scfh
Oil, gph
6841-7
2210 5760
15.8 41.1
25 200 66 500
2520 6650
18.0 47.5
6841-8-B25
Main and Atomizing Air Capacities in scfh
main air pressure drop across burner, osi
Burner
Atomizing
0.5
1
5
6
8
12
16
Air, scfh
designation
0.1
1860 6750
4 160 11 500
5 900 16 500
13 100 36 900
14 400 40 400
16 600
20 400
23 500 66 000
1700 at 20 osi 420 at 15 psi
6841-7
6841-8-B25
46 700 57 200
Metric Conversions
1 osi = 43.94 mm H 2 O = 0.004 39 kg/cm 2
1"wc
= 25.40 mm H = 8.899 kcal/m 3 2 O
1Btu/ft 3
1 psi = 0.0703 kg/cm 2
1" C
= 25.40 mm = 5⁄9 (F – 32)
1 Btu/gal = 0.666 kcal/L
= 0.028 26 sm 3 /h = 0.026 86 nm 3 /h
1 scfh 1gph
1 lb = 0.4536 kg
= 0.001 05 L/s
Excess Air
main air pressure drop across burner, osi
Max % Excess Air
0.1
1
4
8
12
16
6841-7, Gas
– –
250 150 700 550
500 300 120 1030
400 450
375 500 100
350 575 160
6841-7, Oil
6841-8-B25, Gas 6841-8-B25, Oil
160 140
90
1050
1300
1500
With 150 scfh atomizing air at 1 psi.
Without atomizing air.
Flame Length
main air pressure drop across burner, osi
Flame Length, inches
1
4
8
12
16
36 27 24 24
40 27 30 36
50
– –
40 22 48 48
6841-7, Gas 6841-7, Oil
16
6841-8-B25, Gas 6841-8-B25, Oil Flame dia., inches 6841-7, Gas
36-48 36-48
36
36-48
24 18
30
48
– –
24
6841-7, Oil
18
14
15
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