In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.

A.Ash content, carbon residue, and gravity
B.Viscosity, acidity, and demulsibility
C.Pour point, flash, point, and precipitation number
D.Auto-ignition point, viscosity index, and film strength

A.Protects against suction valve float
B.Provides a positive pressure on the air inlet valves
C.Prevents lubricating oil contamination of the compressed air supply
D.Protects against the damaging effects of airborne solid particles

A.warm-up allows the hydraulic system to become charged with oil
B.warm-up allows the relief valves to be properly tested
C.hydraulic strainers operate only during the warm-up period
D.hydraulic fluid must be at the proper viscosity