API-580 Equipment-Specific RBI Applications — Questions and Answers
Question 1: What unique inspection challenges do heat exchangers present in an RBI program?
- Multiple damage mechanisms on tube and shell sides due to different process fluids (Correct answer)
- Heat exchangers never require inspection
- They can only be inspected when fully disassembled
- Only the external surface needs monitoring
Correct answer: Multiple damage mechanisms on tube and shell sides due to different process fluids
Heat exchangers face different damage mechanisms on the tube side versus the shell side due to exposure to different fluids, temperatures, and flow conditions, requiring inspection strategies tailored to each side.
Question 2: How should atmospheric storage tanks be addressed in an RBI program?
- By evaluating both internal corrosion of the floor/shell and external corrosion of the bottom (Correct answer)
- Only by checking the roof for leaks
- By measuring the tank capacity annually
- Atmospheric tanks are exempt from RBI requirements
Correct answer: By evaluating both internal corrosion of the floor/shell and external corrosion of the bottom
Storage tanks require evaluation of internal corrosion (floor and lower shell from product side), external corrosion (tank bottom from soil side), and structural integrity of the roof and shell, per API 653 standards.
Question 3: What is the primary concern for piping systems in an RBI assessment?
- Localized corrosion and erosion at flow changes, welds, and dead legs (Correct answer)
- The color of the pipe insulation
- The distance between pipe supports only
- The brand of pipe fittings used
Correct answer: Localized corrosion and erosion at flow changes, welds, and dead legs
Piping is particularly susceptible to localized damage at elbows, tees, reducers, welds, dead legs, and injection points where flow changes, turbulence, or stagnant conditions accelerate corrosion and erosion.
Question 4: Why do pressure relief devices (PRDs) need RBI evaluation?
- Their failure to operate when needed can lead to catastrophic overpressure events (Correct answer)
- They have the highest purchase cost in the plant
- They are purely decorative safety features
- They only need replacement every 50 years
Correct answer: Their failure to operate when needed can lead to catastrophic overpressure events
PRDs are the last line of defense against overpressure. If they fail to open when needed (fail to danger), catastrophic vessel rupture can occur, making their reliability critical to overall plant safety.
Question 5: How does insulation affect the RBI assessment of piping and equipment?
- Insulation can trap moisture and hide corrosion under insulation (CUI) (Correct answer)
- Insulation always prevents corrosion
- Insulation has no effect on corrosion rates
- Insulated equipment is exempt from inspection
Correct answer: Insulation can trap moisture and hide corrosion under insulation (CUI)
Corrosion under insulation (CUI) is a significant damage mechanism where moisture trapped beneath insulation accelerates external corrosion, particularly in carbon steel operating between 10°F and 350°F (-12°C to 175°C).
Question 6: What special considerations apply to RBI for equipment in cyclic service?
- Fatigue cracking must be evaluated in addition to corrosion-based damage mechanisms (Correct answer)
- Cyclic service eliminates the need for corrosion assessment
- Only visual inspection is required for cyclic equipment
- Cyclic equipment never experiences corrosion
Correct answer: Fatigue cracking must be evaluated in addition to corrosion-based damage mechanisms
Equipment in cyclic service (frequent pressure or temperature cycling) is susceptible to fatigue cracking, which must be assessed alongside corrosion and other damage mechanisms, potentially requiring crack detection inspections.
API-580 Equipment-Specific RBI Applications
What unique inspection challenges do heat exchangers present in an RBI program?