PRINCIPLES OF NAVAL ENGINEERING 



I 1 



SEE ENLARGED VIEW 

 FOR BELLEVILLE 

 SPRING ASSEMBLY 



COVER 

 STUD BOLTS 



GLASS 



ASBESTOS GASKET 



ENLARGED VIEW OF 



BELLEVILLE SPRING ASSEMBLY 



(IN SETS OF SIX SPRINGS) 



ASBESTOS GASKET 

 J MICA GASKET 



^-*^*STAMP 



BRASS GASKET 



CENTERPLATE 

 COVER 



"PLACE THIS SIDE 

 NEXT TO WATER 



Figure 11-28.— Recent type of water gage glass. 



38.239 



A permanent horseshoe magnet is rigidly 

 mounted on that side of the deflection plate 

 which is free to move. The poles of the magnet 

 straddle a tubular well in which a spiral-shaped 

 strip armature is mounted on jeweled bearings. 

 A counterbalanced pointer is attached to the end 

 of the armature mounting shaft. 



When the deflection plate moves in response 

 to variations in pressure, the magnet is made 

 to move along the axisof the well. As the magnet 

 moves the spiral-shaped armature rolls in order 

 to keep in alignment with the magnetic field be- 

 tween the poles of the magnet. Thus a rotary 

 motion is imparted to the armature mounting 

 shaft; and the rotation of the shaft causes the 

 pointer to move. The pointer moves over a 

 brightly illuminated vertical dial which is divided 

 into green and red zones to represent safe and 

 unsafe operating conditions. 



The Jerguson superheater steam flow indi- 

 cator, shown schematically in figure 11-32, 

 consists of three main parts: (1) a datum 

 chamber assembly, (2) a valve manifold, and 

 (3) an indicating unit. 



The Jerguson indicator is essentially a 

 mercury-filled manometer with a stainless steel 

 float in one leg. As the pressure differential 

 between the superheater inlet and the super- 

 heater outlet varies, the mercury level in the 

 instrument changes and thereby actuates the 

 indicating pointer. The movement of the float 

 in the manometer is transmitted to the pointer 

 on the scale by means of a magnetic coupling 

 drive. The coupling consists of an internal 

 magnetic armature on the end of the float shaft 

 and an externalyoke with magnetically energized 

 arms. The yoke, forming a part of the pointer 

 system, pivots on precision bearings in order 



302 



