In what order should bottom blowdown valves be opened and closed?

The correct choice emphasizes the importance of the sequence in which bottom blowdown valves are operated. Opening the valve closest to the boiler first and closing it last is essential for several reasons related to safety and system efficiency.

By opening the closest valve first, it allows for more effective and controlled removal of sediment and impurities from the boiler. This approach ensures that the pressure is released evenly throughout the system, which helps to minimize the risk of shock or rapid pressure change that could lead to damage or operational issues.

Closing the valve closest to the boiler last allows for any remaining sediment or particles to be expelled effectively, ensuring that the system is clean and that no contaminants remain that could affect boiler performance. This sequence also helps maintain the boiler's operational integrity and extends its lifespan by preventing buildup that could lead to scaling or other issues.

In summary, this order of operation ensures safety, efficiency, and effective maintenance of the boiler system.