API-571 Exam Dumps : Corrosion and Materials Professional

API RP 571 on Thermal Fatigue:

“Mixing of hot and cold streams, particularly where hydrogen is present, can induce thermal cycling stresses, leading to thermal fatigue cracking, especially at fittings like tees.”

“Hydrogen embrittlement typically affects stressed zones, but this pattern strongly indicates thermal fatigue.”

So the correct answer is C – Thermal fatigue.

According to API RP 571 Section 5.3.2.1 (Creep):

“Creep damage is exponentially dependent on temperature. A small increase in temperature (e.g., 25°F or 15°C) can reduce remaining life by more than half. This is because the creep rate increases rapidly with temperature, especially above design limits.”

Stress is a contributing factor, but the dominant and most sensitive variable is temperature.

Thus, Option C (increase in temperature of 25°F/15°C) is the correct answer.

Under Thermal Fatigue and Shock, API RP 571 explains:

“Thermal shock damage often initiates at locations with sudden temperature changes, such as quench zones, cold/hot injection points, and areas subjected to rapid cycling.”

“These are critical inspection points for detecting cracking from thermal shock.”

Thus, option B best matches the described mechanism.