Principles of naval engineering - Historic Naval Ships Association

Chapter 10- PROPULSION BOILERSBOILER CASUALTY CONTROLThere are many fireroom casualties whichrequire a knowledge of preventive measuresand corrective measures. Some are major, someare minor; but all can be serious. In the eventof a casualty, the principal doctrine to be impressedupon operating personnel is the preventionof additional or major casualties. Undernormal operating conditions, the safety of personneland machinery should be given firstconsideration. Therefore, it is necessary toknow instantly and accurately what to do foreach casualty. Stopping to find out exactly whatmust be done for each casualty could mean lossof life, extensive damage to machinery, and evencomplete failure of the engineering plant. Afundamental principle of engineering casualtycontrol is split-plant operation. The purpose ofsplit-plant design is to minimize the damagethat might result from any one casualty whichaffects propulsion power, steering, and electricalpower generation.Although speed in controlling a casualty isessential, action should never be taken withoutaccurate information; otherwise the casualtymay be mishandled, and further damage to themachinery may result. Cross-connecting andintact engineering plant with a partly damagedone must be delayed until it is certain that suchaction will not jeopardize the intact one.Cross-connecting valves are provided forthe main and auxiliary steam systems and otherengineering systems so that any boiler or groupof boilers, either forward or aft, may supplysteam to each engineroom. These systems arediscussed in chapter 9 of this manual showingthe construction of the split-plant design onsome types of ships.The discussion of fireroom casualties in thischapter is intended to give you an overall viewof how casualties should be handled. For furtherinformation on casualty control, study the NavalShips Technical Manual , Chapter 9880, and thecasualty control instructions issued for eachtype of ship.Most of the casualties discussed in thischapter are usually treated in a step-by-stepprocedure, but it is beyond the scope of thischapter to give each step in handling eachcasualty. In the step-by-step procedure onestep is performed, then another, then another,and so forth. In handling actual casualties,however, this step-by-step approach will probablyhave to be modified. Different circumstancesmay require a different sequence of steps forcontrol of a casualty. Also, in handling realcasualties several steps will have to be performedat the same time. For example, maincontrol must be notified of any casualty to theboilers or to associated equipment. If "Notifymain control" is listed as the third step incontrolling a particular casualty, does this meanthat the main control is not notified until thefirst two steps have been completed? Not atall. Notifying main control is a step that canusually be taken at the same time other stepsare being taken. It is probably helpful to learnthe steps for controlling casualties in the orderin which they are given; but do not overlookthe fact that the steps may have to be performedsimultaneously.FEED WATER CASUALTIESCasualties in the control of water level includelow water, high water, feed pump casualties,loss of feed suction, and low feed pressure.These casualties are some of the most seriousones.Low water is one of the most serious ofall fireroom casualties. Low water may becaused by failure of the feed pumps, rupturesin the feed discharge line, defective checkvalves, low water in the feed tank, or otherdefects.However, the most frequent cause of lowwater is inattention on the part of the checkmanand the PO in charge of the watch, or the diversionof their attention to other duties. Thecheckman's sole responsibility is to keep thewater in the boiler at a proper level.Low water is extremely damaging to theboiler and may endanger the lives of fireroompersonnel. When the furnace is hot and thereis insufficient water to absorbthe heat, the heatingsurfaces are likely to be distorted, thebrickwork damaged, and the boiler casing warpedby the excessive heat. In addition, serious steamand water leaks may occur as a result of lowwater.Disappearance of the water level from thewater gage glasses must be treated as a casualtyrequiring the immediate securing of the boiler!It should be noted that when the water levelfalls low enough to uncover portions of thetubes, the heat transfer surface is reduced. Asa rule, therefore, the steam pressure will drop.Ordinarily a drop in steam pressure is theresult of an increased demand for steam, and271