🔍 Key Concepts

• Purpose of a surface blow on a boiler (removing floating impurities and scum from the water surface) • How water level in the boiler affects the effectiveness and safety of a surface blow • The relationship between firing rate/steam demand and water level movement during the blow

💭 Think About

• Think about where the impurities and scum you want to remove are located and how the water level should be positioned to sweep them out most effectively. • Consider what will happen to the boiler water level and pressure the moment you crack open the surface blow valve—does it tend to rise or fall? • Ask yourself which option maintains safe boiler operation while still letting you remove as much surface impurity as possible.

✅ Before You Answer

• Verify how a surface blow differs from a bottom blow in both purpose and procedure. • Check what happens to the water level and steam bubbles when you open a surface blow line under normal firing conditions. • Confirm which actions would be unnecessary or unsafe just for a routine surface blow (e.g., taking the boiler offline or making large level changes).