🔍 Key Concepts

• Purpose and risks of blowing down a boiler water wall header • Effect of pressure, temperature, and firing rate on metal stress in boiler components • Difference between operational adjustments (still steaming) vs. shutting down / taking out of service a boiler

💭 Think About

• Before you open any blowdown valve on a high‑pressure part of the boiler, what condition of the furnace and metal temperature will make sudden pressure/flow changes safer? • Which option best reduces thermal and mechanical shock on the water wall tubes while still allowing you to perform a controlled blowdown? • Think about whether a routine header blowdown normally requires a complete shutdown of the boiler, or if it’s done while the unit is still in operation but under modified conditions.

✅ Before You Answer

• Verify which step directly reduces thermal and mechanical stress on the water wall header just before blowdown. • Eliminate any choice that would unnecessarily remove the boiler from service if the procedure is typically done online. • Check which choice is a standard operator’s action to prepare for any sudden change in water circulation and pressure in the water walls.