API 510 Corrosion, Welding & Material Defects 5

Question 1

What is the primary purpose of a corrosion allowance specified in the original design of a pressure vessel?

Accepted Answer

To allow for predictable metal loss over the vessel's intended service life

Answer

The corrosion allowance is extra wall thickness deliberately included in the design to accommodate expected corrosion over the vessel's intended service life without falling below the calculated minimum required thickness.

Question 2

Which weld discontinuity is described as non-metallic material, such as flux or oxide, trapped within the weld metal?

Accepted Answer

Slag inclusion

Answer

Slag inclusions are non-metallic solid materials (flux residue, oxides) entrapped in the weld metal or between weld passes, typically caused by inadequate interpass cleaning or improper welding technique.

Question 3

Hydrogen blistering in pressure vessels typically occurs in which environment?

Accepted Answer

Wet hydrogen sulfide (H2S) or other sour service environments

Answer

Hydrogen blistering occurs in sour (wet H2S) service where atomic hydrogen generated by the sulfide corrosion reaction diffuses into the steel and combines at internal voids or laminations to form H2 gas, causing blisters.

Question 4

According to API 510, which organization's welding standards are typically referenced for repair welding procedures on pressure vessels?

Accepted Answer

ASME Section IX

Answer

API 510 specifies that repair welding must be performed in accordance with ASME Section IX, which governs welding and brazing qualifications including procedure and performance qualifications.

Question 5

What type of corrosion damage is characterized by small, deep, cup-shaped cavities on the metal surface while the surrounding metal remains relatively unattacked?

Accepted Answer

Pitting corrosion

Answer

Pitting corrosion creates localized, deep cavities (pits) on the metal surface while surrounding areas remain largely unaffected, making it particularly dangerous because the small surface area masks the true depth of attack.

(API 510) Certified Pressure Vessel Inspector Practice Test

(API 510) Certified Pressure Vessel Inspector Practice Test

API 510 Corrosion, Welding & Material Defects 5