Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGTOP SHUTOFF VALVEGENERATOR IKKER TUBEGENERATOR OUTER TUBECOPPER TUBE ENDAT GENERATORINNERTUBE COOLINGFINSFigure 11-37.— Single-element feed water regulator.38.184the position of the vane in a nozzle-and-vaneassembly located in the transmitter.A set point knob is linked in some way tothe nozzle of the nozzle-and-vane assembly, sothat the setting of the set point knob affects theposition of the nozzle. The set point knob ispositioned to represent the desired temperatureof the hot water output.The nozzle-and-vane assembly is the comparingand computing device in this pneumatictransmitter. Since the position of the Bourdontube affects the position of the vane and thesetting of the set point knob affects the positionof the nozzle, the distance between the nozzleand the vane at all times represents a comparisonof the actual measured value (Bourdon tube)and the desired value (set point knob). Thedistance between the tip of the nozzle and thevane is responsible for the computation of theamount and direction of change that must bemade in the position of the steam valve, since:(1) the rate of air flow from the nozzle dependsupon the distance between the nozzle andthe vane; and310