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Field Testing for Early Detection of Creep Damage

Background: A client contacted KnightHawk Materials Lab to have some quench exchanger piping analyzed during a turnaround. Because the temperature control in the units had been historically unreliable, the client wanted to have the piping analyzed in the field to determine if early stage creep degradation had occurred.

Figure 1: SEM Micrographs of a Damaged (Left) and Undamaged (Right) Exchanger Pipe


Summary:  KnightHawk performed field metallography to pull replicas of the exchanger pipe microstructures and took field hardness data. Although the majority of the pipes were in good condition, the data from some pipe samples indicated a need for replacement due to microstructural changes and decreases in hardness associated with creep damage. Specifically, the pearlite (shown undamaged on the right in Figure 1) had degraded through a process called spheroidization (shown on the left in Figure 1), and the hardness had decreased by a statistically significant amount, which correlates to a weaker material.

Take Away: There are a wide range of nondestructive testing techniques available to quantify damage after an upset, or even to check on critical systems during routine maintenance or turn-arounds. Use of these techniques can save time and money, by identifying and addressing problem areas when convenient (e.g. during a turnaround) rather than causing downtime or forced outages.