API 510 Material Evaluation and Selection 4

Question 1

How is the Minimum Design Metal Temperature (MDMT) defined for a pressure vessel?

Accepted Answer

The lowest temperature at which the vessel may be subjected to full design pressure

Answer

The MDMT is a design parameter stamped on the nameplate that sets the lower bound for pressurized operation, below which material toughness may be insufficient to prevent brittle fracture.

Question 2

Per ASME Section VIII Division 1 Figure UCS-66, impact testing exemptions for carbon steel are governed by which factors?

Accepted Answer

Material thickness and the exemption curve (A through D) for the specific material specification

Answer

Figure UCS-66 assigns each carbon steel specification to a curve (A–D) based on inherent toughness, then relates nominal thickness to the minimum temperature at which impact testing is exempt.

Question 3

What is the minimum Charpy V-notch energy absorption required for weld metal and HAZ per ASME Section VIII Division 1 UG-84?

Accepted Answer

20 ft-lb (27 J) average with 15 ft-lb (20 J) minimum per specimen

Answer

ASME VIII-1 UG-84 requires a minimum average of 20 ft-lb for the three-specimen set with no single specimen below 15 ft-lb for weld procedure and material qualification.

Question 4

When performing a hydrostatic pressure test at temperatures below the vessel's MDMT, what is the primary risk the inspector must address?

Accepted Answer

Brittle fracture of the pressure-containing shell or nozzles

Answer

Steel tested below its MDMT may have insufficient fracture toughness to resist the stress imposed by the hydrostatic test pressure, leading to brittle fracture.

Question 5

ASTM A516 Grade 70 is frequently selected for low-temperature pressure vessel applications primarily because it is:

Accepted Answer

Produced with killed, fine-grain practice that improves low-temperature toughness

Answer

Killed, fine-grain practice refines the grain size and reduces inclusion content, shifting the ductile-to-brittle transition temperature lower compared to non-fine-grain carbon steel plates.

(API 510) Certified Pressure Vessel Inspector Practice Test

(API 510) Certified Pressure Vessel Inspector Practice Test

API 510 Material Evaluation and Selection 4