PRINCIPLES OF NAVAL ENGINEERING 



RELEASE NUT 



COMPRESSION SCREW 



LEVER PIN 



COMPRESSION 

 SCREW 

 LOCKING NUT 



TOP SPRING 

 WASHER 



LOCKING NUT 



TOP LEVER 



LEVER PIN 



DROP LEVER 



SPRING 



BOTTOM SPRING WASHER 



FEATHER GUIDE 

 RETAINING RING 



FEATHER GUIDE 

 FEATHER 

 HUDDLING CHAMBER 



I 



SEAT BUSHING 



LOCKING SCREW 



SPINDLE 



ACTUAL LOCATION 

 OF RING PIN IS 90° 

 TO THE RIGHT 

 WHEN FACING THE 

 OUTLET 



RING PIN 



ADJUSTING 



y, N.P.T. FOR DRAIN 



BASE 



, SLOTS FOR 

 WRENCHES 



Figure 11-18.— Steam drum safety valve (huddling chamber type). 



98.80 



raising or lowering 

 raising or lowering 



type of valve is made by 

 the adjusting ring and by 

 the nozzle ring. 



Safety valves are always installed at the 

 superheater outlet as well as on the steam drum. 

 Superheater safety valves are set to lift just 

 below, at, or just above the pressure which lifts 

 the steam drum safety valves, in order to en- 

 sure an adequate flow of steam through the 

 superheater when the steam drum safety valves 

 are lifted. 



Most double-furnace boilers are fitted with 

 a pressure-pilot operated superheater outlet 

 safety valve assembly of the type shown in 

 figure 11-20. This assembly consists of three 

 connected valves: a small spring-loaded safety 

 valve installed on the steam drum; an actuating 

 valve installed on the steam drum; and an actu- 

 ated (or unloading) valve installed on the super- 

 heater. The stem of the drum valve is connected 

 mechanically, by means of a lever, to the stem 

 of the actuating valve. The actuating valve is 



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