What happens to the safety factor value if the operating temperature of a vessel operating at maximum allowable working stress is increased?

When the operating temperature of a vessel is increased, especially when it is operating at its maximum allowable working stress, the material properties of the vessel typically change. Most materials will exhibit a decrease in yield strength and tensile strength as temperature rises. This phenomenon occurs because higher temperatures can lead to increased atomic vibrations within the material, resulting in a reduction of its load-bearing capacity.

The safety factor is essentially a ratio that compares the maximum allowable load to the actual operational load. If the material's strength decreases due to the elevated temperature and the operational conditions remain the same, the effective safety margin diminishes. Thus, the safety factor value is reduced in this scenario, reflecting the increased risk associated with operating at higher temperatures.

This principle is vital in the field of engineering, particularly in pressure vessel design, as it emphasizes the need to account for temperature effects on material properties to maintain safe operation.