Chapter 10- PROPULSION BOILERS 



pump in some other space to supply feed to the 

 boiler. If the operating conditions do not allow 

 this solution of the problem, it will be neces- 

 sary to secure the boiler immediately in order 

 to prevent a low water casualty. 



FUEL SYSTEM CASUALTIES 



Casualties to any part of the fuel oil system 

 are serious and must be remedied at once. 

 Common casualties include (1) oil in the fuel 

 oil heater drains, (2) water in the fuel oil, (3) 

 loss of fuel oil suction, (4) failure of the fuel 

 oil service pump, and (5) fuel oil leaks. It 

 should be noted that these casualties to the fuel 

 oil system are for ships burning NSFO. The 

 procedures for ships burning other types of fuel 

 will differ to some extent, but not in all cases. 



Oil leakage from the fuel oil heaters into 

 the drains may cause oil contamination of the 

 drain lines, the reserve feed tanks, the deaerat- 

 ing feed tank, and the feed system piping and 

 pumps. The presence of oil in any part of the 

 feed system is dangerous because of the possi- 

 bility that the oil will eventually reach the 

 boilers, where it will cause steaming difficulties 

 and serious damage to the boilers. 



Fuel oil heater drains must be inspected 

 hourly for the presence of oil. 



The presence of an appreciable amount of 

 water in the fuel oil is indicated by hissing and 

 sputtering of the fires and atomizers and by 

 racing of the fuel oil service pump. The situa- 

 tion must be remedied at once; otherwise, choked 

 atomizers, loss of fires, flarebacks, and re- 

 fractory damage may result. 



A loss of fuel oil suction usually indicates 

 that the oil in the service suction tank has 

 dropped below the level of the fuel oil service 

 pump suction line. This causes a mixture of 

 air and oil to be pumped to the atomizers. The 

 atomizers begin to hiss and the fuel oil service 

 pump begins to race. It must be strongly em- 

 phasized that the loss of fuel oil suction can 

 cause serious results. Related casualties may 

 include loss of auxiliary steam and electric 

 power, with the complete loss of all electrically 

 driven and steam-driven machinery. 



Failure of the fuel oil service pump can 

 cause the same progressive series of casual- 

 ties as those which result from loss of fuel oil 

 suction. 



Fuel oil leaks are very serious, no matter 

 how small they may be. Fuel oil vapors are 



very explosive. Any oil spillage or leakage must 

 be wiped up immediately. 



FLAREBACKS 



A flareback is likely to occur whenever the 

 pressure in the furnace momentarily exceeds 

 the pressure in the boiler air casing. Flare- 

 backs are caused by an inadequate air supply 

 for the amount of oil being supplied, or by a 

 delay in lighting the mixture of air and oil. 



Situations which commonly lead to flare- 

 backs include: (1) attempting to light off or to 

 relight burners from hot brickwork; (2) gunfire 

 or bombing which creates a partial vacuum at 

 the blower intake, thus reducing the air pres- 

 sure supplied by the blowers; (3) forced draft 

 blower failure; (4) accumulation of unburned 

 fuel oil or combustible gases in furnaces, tube 

 banks, uptakes, or air casings; and (5) any 

 event which first extinguishes the burners and 

 then allows unburned fuel oil to spray out into 

 the hot furnace. An example of this last situa- 

 tion might be a temporary interruption of the 

 fuel supply which would cause the burners to 

 go out; when the fuel oil supply returns to 

 normal, the heat of the furnace might not be 

 sufficient to relight the burners immediately. 

 In a few seconds, however, the fuel oil sprayed 

 into the furnace would be vaporized, and a 

 flareback or even an explosion might result. 



SUPERHEATER CASUALTIES 



If the distant-reading superheater thermom- 

 eter does not register a normal increase in 

 temperature when the superheater is first 

 lighted off, the trouble may be either lack of 

 steam flow or failure of the distant-reading 

 thermometer. Lack of steam flow must be con- 

 sidered as a possible cause even if the super- 

 heater steam flow indicator (if installed) shows 

 that there is a flow. If the thermometer does 

 not register a normal increase in temperature, 

 secure all superheater burners. 



When operating with superheat, it is essen- 

 tial to keep a constant check on the flow of steam 

 through the superheater and on the superheater 

 outlet temperature. Any deviation from normal 

 conditions must be corrected without delay. 



It is important to remember that a casualty 

 to some other part of the engineering plant 

 may reduce or entirely stop the flow of steam 

 through the superheater, and so cause a super- 

 heater casualty, unless appropriate action is 



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