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.
Question 2
Temper embrittlement is a metallurgical change that is:
Options:
A.
Not readily apparent but can be confirmed through tension testing
B.
Readily apparent and can be confirmed through impact testing
C.
Readily apparent and can be confirmed through metallography
D.
Not readily apparent but can be confirmed through impact testing
Answer:
D
Explanation:
API RP 571 describes temper embrittlement as a subtle metallurgical change that reduces impact toughness without obvious macrostructural change:
“Temper embrittlement is not readily apparent by visual or standard tensile testing. It is confirmed by Charpy impact testing which measures toughness at low temperatures.”
“It typically affects Cr-Mo steels exposed to intermediate temperatures (650°F to 1100°F) for extended times.”
(Reference: API RP 571, Section 4.2.1.4 – Temper Embrittlement)
Thus, the condition is not visually or physically apparent, but is confirmed through impact testing, making option D correct.
Question 3
The likelihood of brittle fracture is best lessened by:
Options:
A.
Using thicker construction materials to lower the resulting stress
B.
Using carbon or low-alloy steels
C.
Frequent inspection of the piping or equipment involved
D.
Postweld heat treatment (PWHT)
Answer:
D
Explanation:
From API RP 571, brittle fracture prevention measures include:
“Postweld Heat Treatment (PWHT) reduces residual stresses in the heat affected zone and base metal, thus lowering susceptibility to brittle fracture.”
“PWHT is particularly effective when applied to pressure-containing components fabricated from carbon steel or low-alloy steel that will experience low-temperature service.”
(Reference: API RP 571, Section 4.2.1.2 – Brittle Fracture)
Therefore, while other measures may reduce stress or detect flaws, PWHT directly targets one of the root causes: residual stress. Thus, option D is the best prevention method.