Creep and Stress Rupture

Creep and stress rupture is a form of time-dependent deformation and failure that occurs in materials subjected to high temperatures and sustained stress. It is significant concerns in refinery, particularly for high-temperature equipment and components such as reactors, furnaces, piping/tubes, and reformers. It can compromise the integrity and reliability of refinery equipment, leading to costly downtime, maintenance, and potentially hazardous situations.

General Information

Under applied or internal stress and at elevated temperatures, the polycrystalline structure of metal tends to dislocate along the grain boundaries, resulting in the formation of grain boundary voids. These voids weaken the metal’s overall structure, leading to a reduction in its strain properties. This deterioration in mechanical properties can occur even when the stress levels are below the material’s elastic yield stress. The elastic yield stress is the point at which a material begins to deform plastically and will not return to its original shape when the applied stress is removed. When grain boundary voids form, the metal can no longer withstand the same level of stress without deforming, compromising its integrity and performance. Temperature plays a critical role in determining the creep rate, and below a specific level – which varies for different materials – it is generally assumed that creep will not progress, or its rate can be neglected. Table 1 shows some creep threshold temperatures for popular materials.¹

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References

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