API 510 Corrosion, Welding & Material Defects 4

Question 1

In API 510, the 'remaining life' of a pressure vessel is calculated by dividing which two values?

Accepted Answer

Actual thickness minus required thickness by the corrosion rate

Answer

Remaining life = (actual measured thickness − required minimum thickness) ÷ corrosion rate, giving the estimated years before the vessel wall reaches the retirement thickness.

Question 2

Which form of corrosion attacks along grain boundaries of the metal, often caused by chromium depletion in stainless steels?

Accepted Answer

Intergranular corrosion

Answer

Intergranular corrosion in stainless steels is typically caused by sensitization — chromium carbide precipitation at grain boundaries depletes chromium in adjacent zones, making them anodic relative to the grain interior.

Question 3

What is 'lamellar tearing' in the context of weld defects?

Accepted Answer

A subsurface cracking in base metal parallel to the surface caused by through-thickness stresses

Answer

Lamellar tearing occurs in rolled plate when through-thickness welding stresses exceed the low ductility of the plate in the short-transverse direction due to non-metallic inclusions aligned parallel to the plate surface.

Question 4

Which API 510 inspection approach involves using risk assessment to prioritize and set inspection intervals?

Accepted Answer

Risk-based inspection (RBI)

Answer

Risk-based inspection (RBI) uses the probability and consequence of failure to establish inspection priorities and optimize intervals, allowing resources to be focused on higher-risk equipment.

Question 5

Erosion-corrosion in pressure vessels is characterized by accelerated metal loss caused by:

Accepted Answer

Combined mechanical abrasion and corrosive attack from flowing fluid

Answer

Erosion-corrosion occurs when the mechanical action of a flowing fluid (especially with entrained solids or at turbulent zones) removes protective surface films, exposing fresh metal to corrosive attack in a continuous cycle.

(API 510) Certified Pressure Vessel Inspector Practice Test

(API 510) Certified Pressure Vessel Inspector Practice Test

API 510 Corrosion, Welding & Material Defects 4