A.provide a means of draining the boiler
B.warn the engineer of low water level
C.cool the crown sheet at high firing rates
D.open the burners electrical firing circuits

A.the beveled edges of the intake valves provide for serf-centering during seating
B.intake valves utilize stellite-coated valve seat inserts which reduce wear
C.the volume of air passing through intake valves is less than the volume of air passing through exhaust valves
D.intake valves are less affected to the corrosive action of exhaust gases