During an internal inspection, metallurgical examination at a hot spot on a vessel should be conducted if the metal temperature has exceeded what threshold?

In the context of pressure vessel inspection, specific temperature thresholds are critical for determining the need for metallurgical examination. A hot spot on a vessel, indicating that local temperatures may be elevated due to various operational or environmental factors, raises concerns about material integrity.

The threshold of 750°F is established as a critical point at which metallurgical examinations become essential. At temperatures exceeding this level, metallurgical properties of the material can degrade, potentially leading to issues such as embrittlement, reduced toughness, or altered mechanical strength. These changes may not be visible through standard external inspections, making internal metallurgical examination crucial for ensuring the safety and reliability of the vessel.

By conducting a metallurgical inspection at temperatures above 750°F, inspectors can assess potential changes in the material's structure, identify any detrimental effects due to prolonged exposure to high temperatures, and evaluate the need for repair or mitigation strategies to prevent failure. It's a proactive approach to maintaining the integrity and safe operation of pressure vessels under demanding thermal conditions.