PRINCIPLES OF NAVAL ENGINEERING 



conditions. These steam leaks will waste more 

 fuel than could be saved by a few minutes of 

 superheat operation. 



The no-control, integral superheater boiler 

 creates a different types of problem. The super- 

 heater tubes must be protected from the heat of 

 the furnace in the interval during which fires 

 are lighted but the rate of steam generation is 

 still insufficient to ensure a safe flow through 

 the superheater. During operation, there is no 

 problem since all steam passes through the 

 superheater and leaves the boiler at superheat 

 temperature. After the boiler is on the line and 

 furnishing steam, there will be sufficient flow 

 because all steam passes through the super- 

 heater. 



It is sometimes necessary to light off and put 

 additional boilers on the line, when a ship is 

 underway. With no-control superheat boilers, the 

 steps are much the same as for putting the first 

 boiler or boilers onthe line. With superheat con- 

 trol boilers, additional precautions must be 

 taken. 



When the steam lines are carrying super- 

 heated steam, it would be dangerous to admit 

 saturated steam to the lines. It is not usually 

 possible to establish enough steam flow to light 

 off the superheaters of the incoming boilers, 

 until they are on the line. It is permissible to 

 bring in the incoming boilers, without their 

 superheaters in operation, if the superheater 

 outlet temerature of the steaming boilers is 

 lowered to 600° F. Lowering of the superheat 

 temperature on the steaming boilers should be 

 started in time so that the cutting- in tempera- 

 ture can be reached before the incoming boilers 

 are up to operating pressure. Except in an 

 emergency, the temperature of the superheaters 

 should NOT be lowered or raised at a faster 

 rate than 50° F every 5 minutes. 



A number of other items must be checked or 

 inspected at frequent intervals when a ship is 

 underway. Engineeroom personnel must be con- 

 stantly alert for abnormal pressures, temper- 

 atures, sound and vibrations. 



The first indication of bearing trouble is 

 usually a rise in temperature. There is no ob- 

 jection to a bearing running warm as long as 

 the temperature is not high enough to cause 

 damage to the bearing. Any RAPID rise in 

 temperature, or any increase over the normal 

 operating temperature, is probably a sign of 

 trouble. The first things to check are the 

 quantity of lube oil and the quality of lube oil. 

 If possible, the amount of oil going to the over- 

 heated bearing should be increased and the flow 

 of cooling water through the lube oil cooler should 



344 



be increased. If these measures do not reduce the 

 bearing temperature, the unit must be stopped or 

 slowed. 



A sight-flow indicator is fitted in the lube oil 

 line of each main engine bearing and each re- 

 duction gear bearing. When the plant is in op- 

 eration, each sight-flow indicator should always 

 show a steady flow of lube oil. 



The rotor position indicator for each turbine 

 must be checked every hour and the reading 

 must be logged. Any abnormal reading must be 

 investigated at once. 



Once of the first indications of engineroom 

 trouble is an abnormal reading on a thermometer 

 or pressure gage. All gages should be checked 

 frequently. 



The oil level in the main engine sump must 

 be checked every hour and logged in the main 

 engine operating record. In addition, other 

 checks should be made in between the required 

 hourly checks. A rise in the oil level may mean 

 that water is entering the lube oil system or that 

 the system is gaining oil in an abnormal manner. 

 A drop in the oil level of the main engine sump 

 may indicate a leak in the lube oil system or 

 incorrect operation of the lube oil purifier. 



The water level in each operating deaerating 

 feed tank should be kept between the minimum 

 and the maximum allowable levels. If the water 

 level goes above the maximum, the tank no 

 longer deaerates the water. If the water level is 

 below the minimum, a sudden demand for feed 

 water may empty the deaerating feed tank and 

 cause cumulative casualties to the feed booster 

 pump, the main feed pump, and the boilers. 



A salinity indicator is located at or near the 

 throttle board in each engineroom so that engine- 

 room personnel can detect the entrance of salt 

 water into the condensate system. The salinity 

 indicator must be checked constantly. Even a 

 very small amount of salt in the condensate 

 system will very rapidly contaminate a steaming 

 boiler. Any abnormal reading of the salinity 

 indicator must be investigated immediately and 

 the source of contamination must be found and 

 corrected. 



PLANT MAINTENANCE 



The maintenance of maximum operational 

 reliability and efficiency of steam propulsion 

 plants requires a carefully planned and executed 

 program of inspections and preventive mainte- 

 nance, in addition to strict adherence to pre- 

 scribed operating instructions and safety pre- 

 cautions. If proper maintenance procedures are 

 followed, abnormal conditions may be prevented. 



