Chapter 10- PROPULSION BOILERS 



ECONOMIZER TUBES 



STEAM DRUM 



DOWNTAKE NIPPLE 



GENERATING TUBES 



AIR 

 INTAKE 



DOWNTAKE HEADER 



SUPERHEATER TUBES 



WATER SCREEN TUBES 



JUNCTION HEADER 

 (MUD DRUM) 



WATER WALL 

 DOWNTAKE HEADER 



WATER WALL UPTAKE HEADER 



WATER WALL TUBES 



38.34 



Figure 10-16.— Side view of header-type boiler. 



installed in such a way as to form an air cham- 

 ber between the inner and outer casings. The air 

 inlet is at the rear of the boiler; an air duct 

 beneath the furnace floor connects the front air 

 chamber and the rear air chamber. The double- 

 cased air chambers at the sides of the boiler are 

 connected directly to the cold air inlet so that an 

 air pressure is maintained in these side cham- 

 bers at all rates of operation. Removable casing 

 panels are located at various points to permit 

 access for cleaning, inspection, and repair. 



In summary, we may consider the header- 

 type boiler as one which, on the basis of the 



classification methods given earlier in this chap- 

 ter, has the following characteristics: It is a 

 water-tube boiler with natural circulation of the 

 free (not accelerated) type. It has sectional 

 headers instead of water drums, and so is called 

 a "header-type" boiler instead of a drum-type 

 boiler. It has only one furnace— but the term 

 "single-furnace boiler" is never applied to 

 header-type boilers, possibly because such iden- 

 tification has not been needed. It is not a 

 pressurized-furnace boiler. It does not have 

 controlled superheat. It operates at a pressure 

 of 450 to 465 psig; however, header-type boilers 

 are quite often referredtoas "400-psi boilers." 



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