What is saturated steam?

• A. Steam that comes immediately from the drum
• B. Steam that has been cooled and condensed
• C. Steam containing air bubbles
• D. Steam that is completely dry and superheated

Answer: (A)

Saturated steam is steam at its boiling point for the current pressure, in equilibrium with liquid water. It comes directly from the boiler drum where water and steam share the same temperature and pressure, so the steam has not been heated above the saturation temperature. This means it’s ready to be further dried or sent to a superheater if needed, but at this stage it is not superheated.

If steam is cooled, it condenses back to water; if air bubbles are present, you’d have a mixture with non-condensables rather than pure saturated steam; and if it’s completely dry and superheated, its temperature is above the saturation point for that pressure, so it’s not saturated.