Most Recent API-571 Exam Dumps

API RP 571 notes under Sour Water Corrosion:

''Localized thinning or under-deposit corrosion in sour water services is best detected by profile radiography, which provides a visual comparison of wall thickness over a length of pipe.''

''This technique is especially useful for assessing localized metal loss due to under-deposit attack or flow regime effects.''

(Reference: API RP 571, Section 4.3.2.3 -- Sour Water Corrosion)

Hence, profile radiographic testing is most effective, making option B correct.

Comprehensive and Detailed Explanation From Exact Extract:

Per API RP 571, 885 F (475 C) embrittlement primarily affects carbon and low-alloy steels, causing a loss of toughness without obvious microstructural changes visible by routine metallography. Because the damage mechanism manifests as a shift in ductile-to-brittle transition temperature (DBTT), confirmation requires mechanical property testing, not surface or volumetric NDE.

Impact testing (Charpy V-notch) and bend testing are specifically cited as effective methods to demonstrate the loss of toughness and increased brittleness associated with 475 C embrittlement.

Why the other options are incorrect:

Metallography often shows little or no visible change.

Magnetic particle testing only detects surface-breaking flaws.

Ductility testing alone is not as definitive as impact toughness testing.

Referenced Documents (Study Basis):

API RP 571 -- Section on 885 F (475 C) Embrittlement

API Corrosion and Materials Study Guide

According to API RP 571 Section 5.3.2.3 (Spheroidization):

''Spheroidization is the transformation of the microstructure of carbon and low alloy steels when exposed to elevated temperatures for long durations. The rate of spheroidization depends on temperature, prior microstructure, and exposure time... The microstructure becomes less effective at carrying loads, and strength is reduced.''

Key influencing factors for the rate of spheroidization are:

Temperature (higher accelerates the process),

Microstructure (initial phase distribution and morphology).

Pressure and hydrogen partial pressure are not relevant for this transformation, nor is stress a primary driver.

Therefore, Option D (temperature and microstructure) is correct.

API RP 945, dedicated to environmental cracking in amine units, states:

''Carbon steel is widely used in amine systems but is particularly susceptible to localized corrosion, under-deposit corrosion, and stress corrosion cracking, especially in high-pressure or rich amine environments.''

''Proper control of amine quality, oxygen ingress, and temperature is critical to avoid accelerated corrosion in carbon steel equipment.''

Thus, carbon steels are the most commonly affected materials, making option C correct.

API RP 751 (referenced in RP 571) lists materials appropriate for HF acid alkylation service. It specifies:

''Chrome-moly steels such as ASTM A-193 B5 (5% Cr) bolts are preferred for their resistance to HF acid-induced cracking.''

''Standard low alloy steels (e.g., B7) are not considered adequately resistant.''

(Reference: API RP 571 summary & API RP 751, Section 5.6.3 -- Bolting Materials)

Therefore, the correct and industry-approved answer is option A.