What should be monitored to prevent caustic embrittlement in a boiler?

Monitoring water alkalinity levels is crucial in preventing caustic embrittlement in a boiler. Caustic embrittlement occurs when there are high levels of alkaline substances in the boiler water, which can lead to the formation of hydroxides. These conditions contribute to a deterioration of the steel structure of the boiler by causing brittle fractures, especially under high pressures.

By keeping track of the alkalinity, operators can adjust the chemical treatment of the boiler water to maintain an appropriate balance. This ensures that the water chemistry is controlled to avoid excessive alkalinity that leads to caustic conditions.

The other options, while important for overall boiler operation, do not specifically target the prevention of caustic embrittlement. For instance, monitoring feedwater temperature is essential for efficiency and performance but does not directly influence the corrosion phenomena linked to caustic embrittlement. Similarly, while measuring the oxygen content in water is vital for preventing oxidation-related damage, and acidity levels can indicate other corrosion processes, they do not directly address the alkaline conditions that cause caustic embrittlement. Thus, focusing on water alkalinity levels provides a targeted approach for mitigating this specific risk in high-pressure boilers.