Sheet 4723-2 Page 2
Table 3 Air Jet Capacity cfh for all Sizes
Table 5 Pilot Premix Capacity 4723- -G
A pilot orifice is provided with the pilot assembly. The orifice raises the mixture pressure between the mixer and pilot assembly. This improves the pilot premix distribution when multiple tips are used with a common mixer. It also helps reduce combustion pulsations that can extinguish the pilot as the burner cycles from low to high fire. If there is insufficient air pressure available to use the orifice, the mixer should be installed as close as possible to the pilot tip.
Jet pressure osi
cfh 68 85 98
8
12 16
The use of jet air will reduce the maximum excess air limit at low fire rates. Since jet air is intended for use in low excess air conditions this should not be an issue. If higher excess air rates are desired, lowering the jet pressure will increase the excess air limit while still suppressing CO formation.
No Pilot Orifice
Mixer*
pressure
Air cfh 103 150
Min. /Max.
Mixture
Table 4 Minimum Gas Pressure Factors for 10% Excess Air
pressure "w.c.
"w.c.
Gas cfh
8/11
3 6
4.8 9.6
12/16
Burner designation 4723-2-E, G 4723-3-E, G 4723-4-E, G 4723-4B-E, G 4723-5-E, G 4723-6-E, G
With Pilot Orifice (0.219 )
Factor
Mixer*
0.08 0.07 0.06 0.10 0.09
Mixture
pressure
Air cfh 118 155 172
Min. /Max.
pressure "w.c.
"w.c.
Gas cfh
8/11
8
9.8
14
17.6 24.7
12/16 13/18
0.17
20
* Mixer air pressure is measured upstream with a single tip on a 4031 mixer. See Sheet 4011-4 for general mutiple tip information and instructions. Any radiant tube backpressure must be added to the mixture pressures shown. After pilot ignition, the spark should be turned off to prolong electrode life. Spark distributor systems can be used with 4723- -G (but NOT 4723- -E). Pilot air flow should be set between 120-160 cfh. Use a 8666 Testip or sight down the center observation port to set fuel/air ratio in the center of the stability range.
To find approximate minimum natural gas pressure required at burner for Table 1 capacity ratings, multiply high fire air pressure by factor shown. Do not use this table to set air/gas ratios.
Example: 4723-5 with 9.0 osi air pressure at high fire
= 9.0 osi 0.09 (from chart)
= 0.81 osi minimum gas pressure at 10% excess air
SELECTION EXAMPLE Select radiant tube burners for an installation requiring 350 000 Btu/h HHV gross heat release in each tube, with 9 osi air pressure drop across the burners. Solution . To allow for possible adjustment of primary air to 20% for best heat distribution in tubes, divide required capacity by 87.5% (from "notes" under Table 2). To convert cfh air flow to Btu/h HHV multiply air flow by 91 for 10% excess air (100 for stoichiometric ratio). Capacity to use for burner selection = 350 000 (0.875 91) = 408 163 Btu/h HHV. From Table 1, select 4723-4 Burners which are rated at 427 000 Btu/h HHV with 9 osi air. Capacity to use for blower selection = 4270 cfh 1.17 number of burners. (From "notes" under Table 2.) From Table 3, the minimum gas supply pressure should be 0.06 9 osi air pressure = 0.54 osi.
WARNING: Situations dangerous to personnel and property may exist with the operation and maintenance of any combustion equipment. The presence of fuels, oxidants, hot and cold combustion products, hot surfaces, electrical power in control and ignition circuits, etc., are inherent with any combustion application. Components in combustion systems may exceed 160°F (71°C) surface temperatures and present hot surface contact hazard. Fives North American Combustion, Inc. suggests the use of combustion systems that are in compliance with all Safety Codes, Standards, Regulations and Directives; and care in operation.
CONTACT fna.sales@fivesgroup.com T +1 800 626 3477 - F +1 216 373 4237
Fives North American Combustion, Inc. 4455 East 71st Street - Cleveland, OH 44105 - USA www.fivesgroup.com
Made with FlippingBook flipbook maker