Principles of naval engineering - Historic Naval Ships Association

Chapter 12- PROPULSION STEAM TURBINESPreventive inspection and maintenance arevital to successful casualty control, since theseactivities minimize the occurrence of casualtiesby material failures. Continuous and detailedinspection procedures are necessary not onlyto discover partly damaged parts which mayfail at a critical time, but also to eliminate theunderlying conditions which lead to early failure(maladjustment, improper lubrication, corrosion,erosion, and other enemies of machineryreliability). Particular and continuous attentionmust be paid to the following symptoms of malfunctioning:1. Unusual noises.2. Vibrations.3. Abnormal temperatures.4. Abnormal pressures.5. Abnormal operating speeds.Operating personnel should thoroughly familiarizethemselves with the specific temperatures,pressures, and operating speeds of equipmentrequired for normal operation, in orderthat departures from normal operation will bemore readily apparent.If a gage, or other instrument for recordingoperation conditions of machinery, gives anabnormal reading, the cause must be fully investigated.The installation of a spare instrument,or a calibration test, will quickly indicatewhether the abnormal reading is due to instrumenterror. Any other cause msut be traced toits source.Because of the safety factor commonly incorporatedin pumps and similar equipment,considerable loss of capacity can occur beforeany external evidence, is readily apparent.Changes in the operating speeds from normalfor the existing load in the case of pressuregovernor-controlledequipment should be viewedwith suspicion. Variations from normal pressures,lubricating oil temperatures, and systempressures are indicative of either inefficient operationor poor condition of machinery.In cases where a material failure occurs inany unit, a prompt inspection should be made ofall similar units to determine if there is anydanger that a similar failure might occur.Prompt inspection may eliminate a wave of repeatedcasualties.Abnormal wear, fatigue, erosion, or corrosionof a particular part may be indicative of afailure to operate the equipment within its designedlimits or loading, velocity and lubrication,or it may indicate a design or material deficiency.Unless corrective action can be takenwhich will ensure that such failures will notoccur, special inspections to detect damageshould be undertaken as a routine matter.Strict attention must be paid to the properlubrication of all equipment, and this includesfrequent inspection and sampling to determinethat the correct quantity of the proper lubricantis in the unit. It is good practice to make a dailycheck of samples of lubricating oil in all auxilaries.Such samples should be allowed tostand long enough for any water to settle. Whereauxiliaries have been idle for several hours,particularly overnight, a sufficient sample toremove all settled water should bedrainedfromthe lowest part of the oil sump. Replenishmentwith fresh oil to the normal level should be includedin this routine.The presence of salt water in the oil can bedetected by drawing off the settled water bymeans of a pipette and by running a standardchloride test. A sample of sufficient size fortest purposes can be obtained by adding distilledwater to the oil sample, shaking vigorously,and then allowing the water to settlebefore draining off the test sample. Because ofits corrosive effects, salt water in the lubricatingoil is far more dangerous to a unit than is anequal quantity of fresh water. Salt water is particularlyharmful to units containing oillubricatedball bearings.An an example, the maintenance requirementswhich shall be conducted in accordancewith the 3-M System is shown in figure 12-30,(Maintenance Index Page).CASUALTY CONTROLThe mission of engineering casualty controlis to maintain all engineering services in a stateof maximum reliability, under all conditions. Tocarry out this mission, it is necessary for thepersonnel concerned to know the action necessaryto prevent, minimize, and correct theeffects of operational and battle casualties onthe machinery and the electrical and pipinginstallations of their ship. The prime objectiveof casualty control is to maintain a ship as awhole in such a condition that it will functioneffectively as a fighting unit. This requires effectivemaintenance of propulsion machinery,electrical systems, interior and exterior communications,fire control, electronic services,ship control, firemain supply, and miscellaneous345