PRINCIPLES OF NAVAL ENGINEERING 



mixed by spraying the water so that it comes in 

 contact with steam from the auxiliary exhaust 

 line. The quantity of steam must always be pro- 

 portional to the quantity of water, otherwise, 

 faulty operation or a casualty will result. 



Overfilling the deaerating tank may upset the 

 steam-water balance and cool the water to such 

 an extent that ineffective deaeration will take 

 place. Overfilling the deaerating tank also wastes 

 heat and fuel. The excess water, which will have 

 to run down to the condenser, will be cooled— and 

 when it reenters the deaerating tank, more steam 

 will be required to reheat it. If an excessive 

 amount of cold water enters the deaerating feed 

 tank, the temperature drop in the tank will cause 

 a corresponding drop in pressure. As the deaer- 

 ating feed tank pressure drops, more auxiliary 

 exhaust steam enters the tank. This reduces the 

 auxiliary exhaust line pressure, which causes the 

 augmenting valve (150 psi line to auxiliary 

 exhaust line) to open and bleed live steam into the 

 deaerating feed tank. 



When an excessive amount of cold water sud- 

 denly enters the deaerating feed tank, a serious 

 casualty may result . The large amount of cold 

 water will cool (quench) the upper area of the de- 

 aerating feed tank and condense the steam so fast 

 that the pressure is reduced throughout the de- 

 aerating feed tank. This permits the hot conden- 

 sate in the lower portion of the deaerating feed 

 tank and feed booster pump to boil or flash into 

 vapor causing the booster pump to lose suction 

 until the pressure is restored and the boiling of 

 the condensate ceases. With a loss of feed 

 booster pump pressure, the main feed pump suc- 

 tion is reduced or lost entirely, causing serious 

 damage to the feed pump and loss of feed water 

 supply to the boiler(s). Some of the newer ships 

 have safety devices installed on the main feed 

 pumps which will stop the main feed pump when 

 a partial or total loss of main feed booster pres- 

 sure occurs. 



The mixture of condensate, drains, and make- 

 up feed water, constituting the inlet water to the 

 deaerating tank, enters through the tubes of the 

 vent condenser. The condensate pump discharge 

 pressure forces the water through the spray 

 valves of the spray head and discharges it in a 

 fine spray throughout the steam filled top or 

 preheater section of the deaerating feed tank. 



K a spray nozzle sticks open, or if a spray 

 nozzle spring is broken, the flow from the nozzle 

 will not be in the form of a spray and the result 

 will be ineffective deaeration. This condition 

 cannot be discovered except by analysis of the 



feed water leaving the deaerating feed tank, or 

 by inspecting the spray nozzles. 



Inspection of the spray nozzles should be 

 scheduled at frequent intervals. 



In most deaerating feed tanks, the manhole 

 provides access for the inspection of spray 

 nozzles; other tanks are so designed that the 

 spray nozzle chamber and the vent condenser 

 must be removed in order to inspect the nozzles. 



Complete information on constructing and 

 using a test rig for spray valves can be found in 

 chapter 9560 of NavShips Technical Manual. 



SAFETY PRECAUTIONS 

 FOR CONDENSERS 



When opening a main condenser for cleaning 

 or inspection, or when testing a main condenser, 

 there are several safety precautions that must 

 be observed. The following procedures and pre- 

 cautions, when carried out properly, will help 

 prevent casualties to personnel and machinery: 



1. Before the salt water side of a condenser 

 is opened, all sea connections, including the main 

 injection valve, circulating pump suction valve, 

 and main overboard valve, are to be closed tightly 

 and secured against accidental opening with wire, 

 and tagged, DO NOT OPEN, and signed by 

 the person tagging the valve. This is necessary 

 to avoid the possibility of flooding an engineroom. 

 Safety gates, where provided, are to be installed. 



2. On condenser having electrically operated 

 injection and overboard valves, the electrical 

 circuits serving these motors are to be opened 

 and tagged to prevent accidentally energizing 

 these circuits. 



3. Before a manhole or handhole plate is re- 

 moved, drain the salt water side of the condenser 

 by using the drain valve provided in the inlet 

 water box. This is done to make sure that all sea 

 connections are tightly closed. 



4. If practicable, inspection plates are to be 

 replaced and secured before work is discontinued 

 each day. 



5. Never subject condensers to a test pres- 

 sure in excess of 15 psig. 



6. When testingfor leaks, do not stop because 

 one leak is found. The entire surface of both tube 

 sheets must be checked, as other leaks may exist. 

 Determine whether each leak is in the tube joint 

 or in the tube wall, so that the proper repairs can 

 be made. 



7. There is always a possibility that hydro- 

 gen or other gases may be present in the steam 



358 



