Chapter U-ROTT.KR FTTTTNr.S AND PDNTROLS 



COVER PLATE 



ASBESTOS CUS 



ASBESTOS 

 GASKET 



FRAME 



COVER PLATE 



38.238 



Figure 11-27.— Construction of older type of water gage glass. 



measured and transmitted to an indicating 

 dial. 



The Yarway superheater steam flow indi- 

 cator responds to the difference between super- 

 heater inlet pressure and superheater outlet 

 pressure as these two pressures act upon 

 separate columns or heads of water. The gen- 

 eral arrangement of the Yarway superheater 

 steam flow indicator is shown in figure 11-29. 

 A constant water level is maintained in the 

 two head chambers (reservoirs). Both head 

 chambers are in one casting, but the upper head 

 chamber is located slightly above the lower 

 head chamber in order to provide a slight 

 constant pressure differential which serves to 

 stabilize the zero reading. Steam from the 

 superheater inlet is led to the upper head 



chamber, and steam from the superheater out- 

 let is led to the lower head chamber. Exposed 

 piping connects each head chamber with the 

 indicating unit. 



The interior of the indicating unit is shown 

 in figures 11-30 and 11-31. As may be seen, 

 the water from the upper head chamber enters 

 the indicating unit on one side of the diaphragm, 

 and the water from the lower head chamber 

 enters on the other side. The pressure from 

 the upper head chamber is greater than the 

 pressure from the lower head chamber, so the 

 diaphragm is moved accordingly. The diaphragm 

 is connected by a pin linkage to a deflection 

 plate which moves in sensitive response to 

 the movement of the diaphragm. 



301 



