In blowdown with a quick opening and slow opening valve on the bottom blowdown line, which valve is opened first and closed last?

In blowdown with a quick opening and slow opening valve on the bottom blowdown line, which valve is opened first and closed last?

• A. Slow Opening Valve
• B. Quick Opening Valve
• C. Both Opened at the Same Time
• D. Neither Valve is Used

Answer: (B)

Two valves in the bottom blowdown line are used in two stages: a quick-opening valve for a fast purge and a slow-opening valve for a controlled, gradual discharge. The quick-opening valve is opened first to rapidly drop pressure and flush out sediment and sludge from the boiler. After the initial purge begins, the slow-opening valve is opened to maintain a steady blowdown at a safer, controlled rate, which helps prevent water hammer and thermal shock. When shutting down, you close the slow-opening valve first to stop the controlled discharge, and then close the quick-opening valve last to ensure the line is fully shut off. This sequence means the valve opened first is also the one closed last.