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)

Bottom blowdown uses two valves in the discharge line: a fast-opening valve that can be opened quickly to dump water and purge the line, and a slow-opening valve that allows a controlled, gradual flow to avoid pressure surges and water hammer. Opening the fast-opening valve first establishes an immediate path for blowdown so the boiler water level can drop quickly and solids begin to be carried out. Once the initial purge is achieved, the slow-opening valve is used to regulate the remaining blowdown rate to the desired level. When the blowdown is complete, you close the slow-opening valve to stop the regulated flow, and then you close the fast-opening valve last to fully isolate the line. Therefore, the valve opened first and closed last is the quick-opening valve.