REVERSE ANNULUS COMBUSTION

Th

e 4748 is a unique low NOx, high effi

  ciency single ended 

radiant tube burner. Unlike conventional SERT burners, 
combustion occurs in the annulus formed between the outer 
radiant tube and the inner fl ue tube. Combustion gases then 
turn 180° to reverse through the inner fl ue tube to the integral 
high effi

  ciency heat exchanger having a return gas fl ow path 

to conventional SERT burners; hence the name Reverse Annulus 
Single Ended Radiant Tube burner, or "RASERT."

The 4748 RASERT has a number of advantages over 
conventional SERTs. Since the fl ame is in direct contact with 
the inside surface of the radiant tube, heat is transferred to 
the furnace more effi

  ciently. The fl ame propagates outside the 

combustion tube rather than inside, resulting in less thermal 
stress on the combustion tube. RASERT is a patented design 
(#6,321,743) of the Gas Technology Institute (GTI) developed in 
collaboration with North American.

BURNER CAPACITY

The 4748-650 is available in one size. The minimum radiant 
tube inside diameter for this burner is noted in Table 1 below.

Air capacities will be higher when starting the burner in a 
cold environment. Air fl ow will decrease as fl ue gases and 
tube temperatures increase. See page 3 for a detailed graph 
showing fl ue gas oxygen levels 

vs. 

radiant tube temperature. 

Furnace temperatures may cause slight variations in burner 
capacity. Page 4 has further information on radiant tube sizing

. 

Radiant 

Tube

 Burner 

inside 

diameter

designation 

1 osi 

4 osi 

9 osi 

16 osi 

inches

4748-650 

425 

 850 

1300 

1750 

6.50 - 7.38

Air Capacity (scfh at 1650 F furnace temperature) 

with burner air supply pressure of

Table 1

Table 1

—

Low NOx, CO and CO 

2

 emissions achieved by effi  cient

staged combustion, and integral fl ue gas recirculation

—

Compatible with many existing control systems including

simple cross-connected regulator systems

—

Built-in air/fuel metering and gas limiting orifi ce valve mean  

easier installation and commissioning 

—

Direct spark ignition

THE 4748 RASERT

™

 ADVANTAGE:

FLUE OUTLET

FUEL IN

COMBUSTION AIR IN

PRIMAR

Y AIR / FUEL

RETURNED FLUE PRODUCTS

ANNULAR COMBUSTION ZONE

SECONDARY AIR

Bulletin 4748

Page 2

Product Overview | Rasert™