Product Overview | Immersion Tube Burners
pressures must be available. Engineering and application information are presented in Tables I, II, III, and IV, together with a sample calculation to illustrate equipment selection. For special conditions, consult North American. PILOTS/FLAME SUPERVISION A 4021-12 Pilot Tip and 4031 Mixer should be used. A manually lit pilot is not recommended. Pilot regulator must be cross- connected to pilot air line. Flame Supervision : Use flame rod or UV detector. Flame rod should extend 4" beyond outer surface of mounting boss.
4762 HI-CAPACITY Immersion Tube Gas Burners give unsurpassed performance in applications where liquids are heated by direct-fired tubes. Large tanks of liquids are commonly heated by immersion tubes through which burners fire. Flames and flue products scrub inside tube surfaces, rapidly releasing heat to the liquid. This arrangement provides more efficient and economical heating than remote, separately-fired heat sources. 4762 Burners allow high heat releases within confined tubes --higher firing rates in smaller diameter tubes than previously possible, resulting in lower tube costs and smaller tanks. They are sealed-in for full control of air/gas ratio and to permit firing into high backpressure. No refractory tile is used. Flames are extremely stable and quiet burning, operating over a wide range of air/gas ratios. Burners include a primary air adjustment to correct for unusual tube conditions, and an observation port for easy viewing of pilot and main flame. 4762- 4 and -6 Burners have a built-in gas adjustment. A separate 1807 Limiting Orifice Gas Valve is used with -7-A, -7-B, and -8 sizes. OPERATION Accurate air/gas ratio can be obtained by using metering orifices in air and fuel lines, or by analysis of flue products. Although 4762 Burners have wide turndown with normal air/gas ratios, additional turndown is possible by using excess air at low fi re. Control: High-low, high-low-off, modulating or modulating-off (not on-off) control can be used. Easy lighting and smooth operation give safe operation with minimum attention. Pressure Drop in Tubes. High heat releases in small diameter tubes require careful calculation of pressure drops within the tubes to ensure satisfactory operation. Adequate air and gas
SAMPLE SELECTION PROCEDURE
Information Required to Select Equipment:
Heat transfer rate to liquid, load and losses*--for example, 550 000 Btu/hr. Available tank space--for example, enough for 25' of tube with 4 mitered elbows. Fuel--for example, natural gas . Step 1--Effective Tube Length for Heat Transfer. Each elbow or return bend adds 1.1' of effective heat transfer length to the total centerline length (including bends); so Total Effective Length = 25' + (4 × 1.1') = 25' + 4.4' = 29.4' Step 2--Firing Rate. At 550 000 Btu/h HHV in Table I, the next smallest tube length is 28'. This tube length and heat transfer rate result in a required firing rate of 786 000 Btu/h HHV and 70% tube efficiency. (From Table I.)
Then only 28' – 4.4' = 23.6' of tube is needed.
Bulletin 4762 Page 2
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