Chapter 11-BOILER FITTINGS AND CONTROLS 



CAP^«. HEAD CHAMBERS 



CAP 



superheaterX Zsuper- 

 outletA heater 



SETTLING POTS 

 DRAIN VALVES 



INLET 



98.90 

 Figure 11-29.— General arrangement of Yarway 

 superheater steam flow indicator. 



to maintain alignment with the internal armature 

 attached to the float shaft; thus the yoke pivots 

 as the armature moves up and down. 



The datum chamber is connected by piping 

 to the superheater inlet and outlet connections 

 and thus provides the means for impressing dif- 

 ferential pressure on the instrument. As noted 

 previously, the pressure difference between 

 superheater inlet and superheater outlet is used 

 as a measure of the rate of steam flow through 

 the superheater. 



Remote Water Level Indicators 



Remote water level indicators are used on 

 most ships to provide a means whereby the 

 boiler water level may be observed from the 

 lower level of the fireroom. The two types of 

 remote water level indicators discussed here 

 are in common use on combatant ships; other 

 types may be found on auxiliary ships. 



The Yarway remote water level indicator 

 consists of three parts: (1) a constant-head 

 chamber which is mounted on the steam drum 

 at or near the vertical centerline of the drum- 

 head; (2) a graduated indicator which is usually 

 mounted on an instrument panel; and (3) two 

 reference legs that connect the constant-head 

 chamber to the indicator. The reference legs 

 are marked A and B in figure 11-33, which 

 shows the general arrangement of a Yarway 

 remote water level indicator. 



A constant water level is maintained in 

 leg A, since the water level in the constant- 

 head chamber does not vary. The level in leg 

 B is free to fluctuate with changes in the 

 steam drum water level. The upper hemisphere 

 of the constant-head chamber is connected to 

 the steam drum at a point above the highest 

 water level to be indicated; because of this 

 connection, boiler pressure is exerted equally 

 upon the water in the two legs. The variable 

 leg B is connected to the steam drum at a point 

 below the water level to be indicated; because 

 of this connection, the water level in leg B is 

 equalized with the water level in the steam drum. 



As may be seen in figure 11-33, each leg 

 is connected by piping to the indicator. In the 

 indicator, the two columns of water terminate 

 upon opposite sides of a diaphragm. The in- 

 dicating unit is almost identical with the in- 

 dicating unit of the Yarway superheater steam 

 flow indicator, previously described. 



The general arrangement of a Jerguson 

 remote water level indicator is shown in figure 

 11-34, As may be seen, the operating prin- 

 ciples of this device are very similar to the 

 operating principles of the Jerguson steam 

 flow indicator, previously discussed. 



Superheater Temperature Alarms 



Superheater temperature alarms are in- 

 stalled on most boilers to warn operating per- 

 sonnel of dangerously high temperatures in the 

 superheater. One type of superheater temper- 

 ature alarm is shown in figure 11-35. The bulb. 



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