Chapter 10- PROPULSION BOILERS 



enormous heat losses. The blowerman must 

 learn by experience how much air pressure 

 should be shown on the air pressure gage for 

 all the various combinations of different num- 

 bers of burners, different sizes of sprayer 

 plates, and different fuel pressures. 



The number of men assigned to operate the 

 fireroom auxiliary machinery varies from one 

 ship to another, depending upon the size of the 

 ship and the number of men available. Some 

 ships may have two or more men assigned to 

 this duty; on other ships, the work may be done 

 by the petty officer in charge of the watch or 

 by the messenger. The burnerman and the 

 blowerman may also take care of some of the 

 auxiliaries. The checkman must never be given 

 any duties other than his primary ones of watch- 

 ing and maintaining the water level. 



All fireroom operations are supervised and 

 coordinated by the petty officer in charge of the 

 watch. The petty officer in charge of the watch 

 supervises all lighting off, operating, and se- 

 curing procedures. He keeps the engineroom 

 and the engineering officer of the watch in- 

 formed of operating conditions when necessary. 

 He must be constantly alert to the slightest 

 indication of trouble and must be constantly 

 prepared to deal with any casualty that may 

 occur. The petty officer in charge of the watch 

 is responsible for making sure that all safety 

 precautions are being observed and that unsafe 

 operating conditions are not allowed to exist. 



FIREROOM EFFICIENCY 



The military value of a naval vessel depends 

 in large measure upon her cruising radius, 

 which, in turn, depends upon the efficiency with 

 which the engineering plant is operated. Perhaps 

 the largest single factor in determining the 

 efficiency of the engineering plant is the effi- 

 ciency with which the boilers are operated. 

 Greater savings in fuel, with consequent increase 

 in steaming radius of the ship, may often be 

 made in the fireroom than in all the rest of the 

 engineering plant put together. 



The capacity of a boiler is defined as the 

 maximum rate at which the boiler can generate 

 steam. The rate of steam generation is usually 

 expressed in terms of pounds of water evapo- 

 rated per hour. You should know something of 

 the limitations upon boiler capacity, the sig- 

 nificance of full-power and overload ratings, 

 and the procedure for checking on boiler loads. 



The capacity of any boiler is limited by 

 three factors that have to do both with the design 

 of the boiler and with its operation. These lim- 

 itations, which are known as end points , are 

 (1) the end point for combustion, (2) the end 

 point for moisture carryover , and (3) the end 

 point for water circulation. 



Boilers are so designed that the end point 

 for combustion should occur at a lower rate of 

 steam generation than the end point for mois- 

 ture carryover, and the end point for moisture 

 carryover at a lower rate than the end point for 

 water circulation. Since the end point for com- 

 bustion occurs first, it is the only end point that 

 is likely to be reached in a properly designed 

 and properly operated boiler. However, it should 

 be understood that it is quite possible to reach 

 the end points for moisture carryover and water 

 circulation before reaching the end point for 

 combustion, by using larger sprayer plates than 

 those recommended by the manufacturer or by 

 the Bureau of Ships. In such a case, the boiler 

 might suffer great damage before the end point 

 for combustion was reached. 



End Point for Combustion 



The process of burning fuel in a boiler 

 furnace involves forcing the fuel into the furnace 

 at the proper viscosity through atomizers which 

 break up the oil into a foglike spray, and forcing 

 air into the furnace in such a way that it mixes 

 thoroughly with the oil spray. The amount of fuel 

 that can be burned is limited primarily by the 

 actual capacity of the equipment that supplies 

 the fuel (including the capacity of the sprayer 

 plates), by the amount of air that can be forced 

 into the furnace, and by the ability of the burner 

 apparatus to mix this air with the fuel. The 

 volume and shape of the furnace are also limit- 

 ing factors. 



The end point for combustion for a boiler is 

 reached when the capacity of the sprayer plates, 

 at the designed pressure for the system, is 

 reached or when the maximum amount of air 

 that can be forced into the furnace is insufficient 

 for complete combustion of the fuel. If the end 

 point for combustion is actually reached because 

 of insufficient air, the smoke in the uptakes will 

 be black because it will contain particles of 

 unburned fuel. However, this condition should be 

 rare, since the end point for combustion is 

 artificially limited by sprayer plate capacity 

 when the fuel is supplied at the burner manifold 

 at designed operating pressure. As noted before, 



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