This course is designed to familiarize participants with the basic principles associated with the flow of water and steam in various types of boilers. After completing this course, participants should be able to describe the flow path of water through a typical drum-type boiler, explain the differences between natural circulation and controlled circulation, and describe the functions and components of a typical boiler drum. They should also be able to describe the flow path of steam from the boiler to the condenser in a typical generating unit and explain the function of each component in the flow path. In addition, participants should be able to explain why some boilers operate above the critical point, describe the flow path of water in a once-through supercritical boiler, and explain how steam pressure is maintained in a drum-type boiler and in a once-through boiler.