PRINCIPLES OF NAVAL ENGINEERING 



the headers, serves as a telltale^ in the event of 

 handhole leakage in the economizer. 



Superheater vents are installed at or near 

 the top of each superheater header or header 

 section; superheater drains are installed at or 

 near the bottom of each header or header sec- 

 tion. Thus each pass of the superheater is 

 vented and drained. 



Superheater drains discharge through gravity 

 (open-funnel) drains to the fresh water drain 

 collecting system while steam is being raised 

 in the boiler. After a specified pressure has 

 been reached, the superheater drains are shifted 

 to discharge through steam traps^ to the high 

 pressure drain system. The steam traps allow 

 continuous drainage of the superheater without 

 excessive loss of steam or pressure. 



Figure 11-14 illustrates diagrammatically 

 the arrangement of superheater vents and drains 

 on a newer type of single-furnace boiler. This 

 illustration also shows the superheater protec- 

 tion steam connections. Note, also, the water- 

 drum installation of the desuperheater. 



Sampling Connections 



It is difficult to say just where the connec- 

 tion for drawing test samples of boiler water 

 may be located, since this connection is found 

 in different places on different types of boilers. 

 On some boilers the sampling connection is 

 located at the rear of the water drum. On others 

 it comes off of the bottom blow line between 

 the water drum and the bottom blow valve, 

 either at the front of the boiler or at about the 

 middle of the water drum. On boilers that have 

 a chemical feed pipe in the steam drum, the test 

 samples may be drawn through the nozzle con- 

 nection of the chemical feedpipe. On some ships 

 the surface blow line connection is used to take 

 boiler water samples. 



It is also difficult to say just what the sam- 

 pling connection may be called. On some draw- 

 ings it is identified as a test cock; on others 

 as a salinity cock; on others as a salinometer 

 valve; and on still others as a water test sample 

 connection. 



A sample cooler is fitted to the outlet side 

 of the sampling connection. The cooler brings 



the temperature of the sample water down below 

 the boiling point at atmospheric pressure and 

 thus keeps the water from flashing into steam 

 as it is drawn from the higher pressure of the 

 boiler to the lower pressure of the fireroom. 



Feed Stop and Check Valves 



Manually operated feed stop and check valves 

 are installed in the feed line to each boiler."* 

 Feed stop and check valves are operated man- 

 ually, with a separate handwheel for each valve. 

 In addition, the feed check valve has remote 

 operating gear so that it can be operated from 

 the firing aisle. In normal operation, the stop 

 valve is kept fully open and the check valve is 

 used to regulate the supply of feed water to the 

 boiler. When automatic feed water controls are 

 in use, both the feed stop valve and the feed 

 check valve are kept fully open so that they will 

 not interfere with the automatic feeding of the 

 boiler. (Similarly, the automatic feed regulating 

 valve is kept fully open when the boiler is being 

 fed manually through the feed check valve. 



The feed stop and check valves shown in 

 figure 11-15 are combined in one manifold cast- 

 ing. Note, however, that there are two separate 

 valves. In some installations the two valves are 

 housed in separate flanged castings which are 

 bolted together. No matter what type of instal- 

 lation is used, the feed stop valve is always in- 

 stalled between the feed check valve and the 

 economizer inlet. 



Steam Stop Valves 



Main steam stop valves are used to cut 

 boilers in on the main steam line and to dis- 

 connect them from the line. The main steam 

 stop valve located just after the superheater 

 outlet is usually called the main steam boiler 

 stop. Figure 11-16 shows an external view of 

 a main steam boiler stop. Figure 11-17 shows 

 a cross-sectional view of a globe-type main 

 steam boiler stop. Gate valves instead of globe 

 valves are used as main steam boiler stops on 

 many newer ships. 



The term telltale is frequently used in connection 

 with engineering equipment to indicate any device which 

 shows leakage, flow, position, or other conditions. 

 3 



Steam traps are discussed in chapter 14 of this text. 



The stop valve is a regular globe-type stop valve. 

 The so-called "check" valve is actually a stop-check 

 valve which functions either as a stop valve or as a 

 check valve, depending upon the position of the valve 

 stem. 



288 



