API 510 Code Requirements 2 — Questions and Answers
Question 1: According to API 510, what is the minimum required thickness (Tmin) concept used for?
- To set the design wall thickness for new construction
- To determine the thickness below which a component is no longer fit for continued service (Correct answer)
- To establish the nominal thickness stamped on the nameplate
- To calculate corrosion allowance for future inspections
Correct answer: To determine the thickness below which a component is no longer fit for continued service
Tmin is the minimum required thickness below which a pressure vessel component cannot remain in service without repair, alteration, or retirement.
Question 2: Under API 510, which of the following conditions requires an on-stream inspection rather than an internal inspection?
- When the corrosion rate is unknown
- When the vessel has been in service for more than 10 years
- When entry is physically impossible or creates a greater hazard than the inspection itself (Correct answer)
- When the vessel operates above 650°F
Correct answer: When entry is physically impossible or creates a greater hazard than the inspection itself
API 510 permits on-stream inspection as an alternative to internal inspection when vessel entry is impractical or would create a greater hazard.
Question 3: API 510 defines the term 'pressure-containing parts' to include which of the following?
- Only the shell and heads of the vessel
- Shells, heads, nozzles, manways, and other components exposed to internal pressure (Correct answer)
- Only components that are welded to the vessel shell
- Insulation supports and fireproofing attachments
Correct answer: Shells, heads, nozzles, manways, and other components exposed to internal pressure
Pressure-containing parts include all components that form the pressure boundary, such as shells, heads, nozzles, and manways.
Question 4: When API 510 allows the next inspection interval to be set based on half-life, what does 'half-life' mean?
- Half the original design life of the vessel
- Half the time it would take for corrosion to reduce wall thickness to Tmin (Correct answer)
- Half the time since the last inspection
- Half the corrosion rate established in the previous period
Correct answer: Half the time it would take for corrosion to reduce wall thickness to Tmin
Half-life is the time it would take corrosion to consume half the remaining corrosion allowance (i.e., half the time to reach Tmin).
Question 5: According to API 510, what is the maximum inspection interval for an internal or on-stream inspection of a pressure vessel in typical service?
- 5 years
- 10 years (Correct answer)
- 15 years
- 20 years
Correct answer: 10 years
API 510 sets a maximum interval of 10 years for internal or on-stream inspection, unless a longer interval is justified by RBI.
Question 6: Under API 510, who has the authority to approve an extension of the maximum inspection interval beyond the code limits using risk-based inspection (RBI)?
- The vessel owner/operator alone
- The authorized inspection agency
- The owner/operator with concurrence from the inspector and an engineer (Correct answer)
- Only the jurisdiction authority
Correct answer: The owner/operator with concurrence from the inspector and an engineer
RBI-based interval extensions require concurrence from the inspector and an engineer experienced in pressure vessel technology, with the owner/operator responsible for the program.
Question 7: API 510 requires that inspection records include which minimum piece of information for each thickness measurement location?
- The name of the ultrasonic equipment manufacturer
- The location of the measurement, thickness reading, and date (Correct answer)
- The ambient temperature during the inspection
- The inspector's personal certification number only
Correct answer: The location of the measurement, thickness reading, and date
Inspection records must identify the measurement location, the actual thickness reading, and the date of measurement to enable corrosion rate calculations.
API 510 Code Requirements 2
According to API 510, what is the minimum required thickness (Tmin) concept used for?