API 510 Pressure Testing Procedures 5 — Questions and Answers
Question 1: Under what condition may an API 510 inspector waive a pressure test entirely for a vessel that has undergone major repair?
- Only with documented engineering analysis demonstrating continued fitness-for-service without testing (Correct answer)
- Whenever the operator requests a waiver
- When the vessel is older than 20 years and fully corroded
- When the repair cost is less than 50% of replacement cost
Correct answer: Only with documented engineering analysis demonstrating continued fitness-for-service without testing
A major repair waiver requires documented engineering justification confirming the vessel remains fit-for-service without a pressure test.
Question 2: If a hydrostatic test reveals a leak at a threaded connection, the correct action before retesting is to:
- Apply thread sealant and retighten the connection, then retest (Correct answer)
- Replace the entire nozzle assembly
- Increase the test pressure to overcome the leak
- Accept the leak if it is less than one drop per minute
Correct answer: Apply thread sealant and retighten the connection, then retest
Minor threaded connection leaks can be corrected by applying appropriate sealant and retightening before conducting a new test.
Question 3: API 510 requires that the results of each pressure test be documented. Which of the following must be recorded as a minimum?
- Test pressure, test medium, hold time, temperature, and test result (pass/fail) (Correct answer)
- Only the final test pressure and date
- The name of the inspector's supervisor
- The cost of the test fluid used
Correct answer: Test pressure, test medium, hold time, temperature, and test result (pass/fail)
Complete pressure test records per API 510 must include the test pressure, medium, hold time, temperature, and the outcome of the test.
Question 4: When a vessel has an internal lining, such as a refractory or rubber lining, how does this affect pressure testing requirements?
- The lining must be inspected and its condition considered before the test to avoid damage from test pressure (Correct answer)
- The lining eliminates the need for a pressure test
- The test pressure must be reduced by 50% for lined vessels
- Lined vessels are exempt from API 510 pressure testing requirements
Correct answer: The lining must be inspected and its condition considered before the test to avoid damage from test pressure
Internal linings can be damaged by pressure testing if they are unbonded or cracked, so their condition must be evaluated before a test is performed.
Question 5: For pressure vessels in lethal service, what additional requirement applies to pressure testing compared to non-lethal service vessels?
- Full radiographic examination of all pressure joints is required in addition to the pressure test (Correct answer)
- The test pressure must be 3.0 times MAWP instead of 1.3 times
- Only pneumatic testing is permitted
- Hydrostatic testing is not required for lethal service vessels
Correct answer: Full radiographic examination of all pressure joints is required in addition to the pressure test
Vessels in lethal service require full radiography of all pressure joints per ASME Section VIII Division 1, providing additional assurance beyond pressure testing alone.
Question 6: When using a pressure-measuring system during a test, API 510 recommends that gauge calibration be verified within how long before the test?
- Within a recent, documented calibration period appropriate to the owner's quality program, typically within one year (Correct answer)
- Within 24 hours of the test
- Within 5 years
- Calibration is not required if the gauge looks undamaged
Correct answer: Within a recent, documented calibration period appropriate to the owner's quality program, typically within one year
Gauges must be within their current calibration cycle per the owner's QA program; a one-year interval is typical practice in the industry.
Question 7: What is the significance of the term 'test pressure at the top of the vessel' versus 'test pressure at the pump' during a hydrostatic test?
- The pressure at the top of the vessel is lower due to the hydrostatic head of fluid, so the pump must develop higher pressure to achieve the required test pressure at the top (Correct answer)
- The pressure at the top is always higher because the pump supplies excess pressure
- There is no difference because fluid distributes pressure equally in all directions
- The pump pressure must equal exactly the MAWP, regardless of vessel elevation
Correct answer: The pressure at the top of the vessel is lower due to the hydrostatic head of fluid, so the pump must develop higher pressure to achieve the required test pressure at the top
The hydrostatic head of water in a tall vessel reduces pressure at the top relative to the pump, so the pump pressure must compensate to achieve the required test pressure at the vessel's highest point.
API 510 Pressure Testing Procedures 5
Under what condition may an API 510 inspector waive a pressure test entirely for a vessel that has undergone major repair?