PRINCIPLES OF NAVAL ENGINEERING 



the natural tendency is to cut in more burners 

 to fulfill the demand. If the drop in steam pres- 

 sure is caused by low water, however, increas- 

 ing the firing rate will result in serious damage 

 to the boiler and possibly in injury to fireroom 

 personnel. The possibility that a drop in steam 

 pressure indicates low water must always be 

 kept in mind! Always check the level in the 

 water gage glasses before cutting in additional 

 burners, when steam pressure has dropped for 

 no apparent reason. 



High water is another serious casualty that 

 is most frequently caused by the inattention of 

 the checkman and the PO in charge of the watch. 

 If the water level in the gage glass goes above 

 the highest visible part, the boiler must be 

 secured immediately. 



By careful observation, it is sometimes pos- 

 sible to distinguish between an empty gage glass 

 and a full one by the presence or absence of 

 condensate trickling down the inside of the 

 glass. The presence of condensate indicates, 

 of course, an empty glass— that is, a low water 

 casualty. However, the boiler must be secured 

 whether the water is high or low. After the 

 boiler has been secured, the location of the 

 water level can be determined by using the 

 gage glass cutout valves and drain valves. 



Failure of a feed system pump can have 

 drastic consequences. Unless the pump casualty 

 is corrected immediately, the pump failure 

 will lead to low water in the boiler. In addition 

 to the obvious dangers associated with low 

 water, there are some which are equally serious 

 but not so obvious. For example, low water 

 causes complete or partial loss of steam pres- 

 sure. When steam pressure is lost or greatly 

 reduced, you will lose the services of vital 

 auxiliary machinery— pumps, blowers, and so 

 forth. It is essential, therefore, that feed pump 

 casualties be handled rapidly and correctly. 



If the main feed pump discharge pressure 

 is too low, the first three things to be checked 

 are (1) the feed booster pump discharge pres- 

 sure, (2) the level and pressure in the deaerat- 

 ing feed tank, and (3) the feed stop and check 

 valves on idle boilers. A failure of the feed 

 booster pump will, of course, cause loss of 

 suction and, therefore, loss of discharge pres- 

 sure of the main feed pump. If the feed stop 

 and check valves on idle boilers have acciden- 

 tally been left open, the main feed pump dis- 

 charge pressure may be low merely because 

 water has been pumped to an idle boiler, as 

 well as to the steaming boiler. 



Some of the most likely causes of failure of 

 the main feed pump are (1) malfunction of the 

 constant-pressure pump governor, (2) and air- 

 bound or vapor-bound condition of the main 

 feed pump, (3) faulty pump clearances, and (4) 

 malfunction or improper setting of the speed- 

 limiting governor. 



In many installations, the feed booster pump 

 and the main feed pump are in the engineroom. 

 In other installations, the feed booster pump is 

 in the engineroom but the main feed pump is in 

 the fireroom. In this latter type of installation, 

 failure of the feed booster pump will be indi- 

 cated to the fireroom force by loss of main 

 feed pump discharge pressure and by the sound- 

 ing of the low pressure feed alarm that is 

 usually fitted where this type of machinery 

 arrangement exists. The casualty to the feed 

 booster pump will be dealt with by engineroom 

 personnel, if the pump is in the engineroom; 

 but fireroom personnel must take immediate 

 action to maintain a supply of feed water to the 

 boiler. 



If the engineroom is unable to remedy the 

 situation immediately, start the emergency 

 feed pump on cold suction . The emergency 

 feed pump can take a hot suction from the feed 

 booster pump, or a cold suction from the re- 

 serve feed tanks. In standby condition, this 

 pump should always be lined up on cold suction. 



If the main feed pump fails and there is no 

 standby pump available, start the emergency 

 feed pump on hot suction and continue to feed 

 the boiler. If the feed also fails then it will be 

 necessary to start the emergency feed pump on 

 cold suction. 



If the emergency feed pump fails, the pro- 

 cedures for handling the casualty will vary 

 according to the situation existing at the time 

 of the failure. 



In many ships, the emergency feed pump is 

 normally used for in-port operation, with the 

 main feed pump in standby condition and the 

 feed booster pump providing a hot suction for 

 the emergency feed pump. Under these condi- 

 tions, emergency feed pump failure can be 

 handled by notifying the engineroom so that the 

 main feed pump can be put on the line and used 

 to feed the boiler. 



A more difficult problem will arise if the 

 emergency feed pump fails when it isbeingused 

 because of a previous casualty to the feed 

 booster pump or to the main feed pump. Under 

 these conditions, it may be possible to deal with 

 the situation by cross-connecting and using a 



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