API 653 Pressure Testing 5 — Questions and Answers
Question 1: According to API 653, after completing a successful hydrostatic test, what must be done with the test records?
- Retained by the authorized inspector for 1 year
- Included in the tank's permanent file maintained by the owner/operator (Correct answer)
- Submitted to the API for archival
- Discarded after the tank returns to service
Correct answer: Included in the tank's permanent file maintained by the owner/operator
API 653 requires that all hydrostatic test records become part of the tank's permanent file, retained by the owner/operator for the life of the tank.
Question 2: When a tank shell repair involves installing a flush patch plate, API 653 requires the completed patch weld to be tested by:
- Visual examination only if thickness is less than 0.5 in
- Hydrostatic test or other leak test acceptable to the engineer (Correct answer)
- Pneumatic bubble test at 15 psi minimum
- Dye penetrant test on the exterior surface only
Correct answer: Hydrostatic test or other leak test acceptable to the engineer
API 653 requires flush shell patch welds to be verified by hydrostatic test or another leak test method acceptable to the engineer of record.
Question 3: Which API 653 provision allows an inspector to accept a repaired tank into service WITHOUT performing a new hydrostatic test?
- When the repair affects only the external coating system
- When the tank was originally built to API 650 and is re-rated to a lower fill height
- When repair welds are fully radiographed and meet API 650 acceptance criteria
- Both A and C (Correct answer)
Correct answer: Both A and C
API 653 allows bypass of hydrostatic retesting when repairs are limited to non-pressure items (coating) or when pressure-retaining weld repairs are fully radiographed to API 650 standards.
Question 4: During a hydrostatic test in cold climates, what precaution does API 653 recommend to prevent shell brittle fracture?
- Pre-heat the shell to 200°F before filling
- Use heated water to keep shell metal temperature above the minimum design metal temperature (MDMT) (Correct answer)
- Apply insulation blankets to maintain ambient temperature inside the tank
- Limit fill rate to less than 1 ft/hr in temperatures below 50°F
Correct answer: Use heated water to keep shell metal temperature above the minimum design metal temperature (MDMT)
API 653 recommends using heated water so that the shell metal temperature remains above the MDMT, preventing brittle fracture during the hydrostatic test.
Question 5: What does API 653 require an authorized inspector to verify about the tank's venting system before starting a hydrostatic fill?
- That all vents are sealed to maintain pressure during the test
- That adequate venting exists to prevent vacuum or over-pressure conditions during filling and emptying (Correct answer)
- That the pressure-vacuum valve is set to 2 oz/in² above test pressure
- That all roof drain valves are closed and locked out
Correct answer: That adequate venting exists to prevent vacuum or over-pressure conditions during filling and emptying
The inspector must confirm adequate venting is available to prevent tank vacuum collapse during draining and overpressure during filling before the hydrostatic test begins.
Question 6: For an API 653 reconstructed tank with a new bottom installed, what is the required sequence of testing operations?
- Shell hydrostatic test first, then bottom leak test
- Bottom leak test first, then hydrostatic shell test (Correct answer)
- Both tests performed simultaneously during the fill
- Bottom leak test is optional if shell radiography passes
Correct answer: Bottom leak test first, then hydrostatic shell test
API 653 requires the bottom leak test (vacuum box or equivalent) to be completed before the hydrostatic fill so that bottom defects can be repaired without draining the full shell.
Question 7: Under API 653, if hydrostatic test water will remain in a carbon steel tank for more than 30 days, what must the owner/operator consider?
- Mandatory nitrogen blanketing of the water surface
- Corrosion inhibitor addition or other measures to prevent internal corrosion during the extended test hold (Correct answer)
- Draining and refilling with fresh water every 30 days
- Installing a cathodic protection system before the test
Correct answer: Corrosion inhibitor addition or other measures to prevent internal corrosion during the extended test hold
API 653 notes that if test water is retained for extended periods, the owner/operator should add corrosion inhibitors or take other steps to prevent accelerated internal corrosion of the tank bottom and shell.
API 653 Pressure Testing 5
According to API 653, after completing a successful hydrostatic test, what must be done with the test records?