API 653 Pressure Testing 2 — Questions and Answers
Question 1: According to API 653, what is the minimum hold time for a hydrostatic test on a reconstructed tank before inspection begins?
- 15 minutes
- 30 minutes
- 1 hour (Correct answer)
- 24 hours
Correct answer: 1 hour
API 653 requires the hydrostatic test pressure to be held for at least 1 hour before the inspection of the shell and bottom is performed.
Question 2: When performing a hydrostatic test on an aboveground storage tank, the test water temperature should be maintained above what minimum to prevent brittle fracture?
- 32°F (0°C)
- 40°F (4°C) (Correct answer)
- 50°F (10°C)
- 60°F (16°C)
Correct answer: 40°F (4°C)
API 653 requires that the hydrostatic test water temperature be maintained above 40°F (4°C) to avoid brittle fracture of the shell material.
Question 3: Which API 653 alternative to a full hydrostatic test requires the tank bottom to be inspected using a sensitive leak detection method such as vacuum box or magnetic flux leakage?
- Pneumatic shell test
- Reduced hydrostatic test
- Inspection in lieu of hydrostatic test (Correct answer)
- Spot radiography alternative
Correct answer: Inspection in lieu of hydrostatic test
API 653 Section 12 allows an inspection in lieu of hydrostatic testing when the bottom is examined by an acceptable leak detection method.
Question 4: During a hydrostatic test of a repaired tank, where should settlement measurements be taken and recorded?
- Only at the fill nozzle
- At equally spaced points around the tank periphery (Correct answer)
- At the highest shell course only
- At the tank center and one edge point
Correct answer: At equally spaced points around the tank periphery
API 653 requires settlement measurements to be taken at equally spaced points around the tank periphery to detect differential settlement during filling.
Question 5: What action must be taken if a leak is discovered in the shell during a hydrostatic test under API 653?
- Continue testing and note the location
- Immediately reduce water level and repair before retesting (Correct answer)
- Apply an external sealant and continue the test
- Increase test pressure to seat the leak
Correct answer: Immediately reduce water level and repair before retesting
Any shell leak found during hydrostatic testing requires immediate depressurization to a safe level, repair of the defect, and a retest.
Question 6: For an API 653 hydrostatic test, the test fill level is typically filled to what level relative to the design fill height?
- 50% of design fill height
- 75% of design fill height
- The design maximum fill height or overflow level (Correct answer)
- 110% of design fill height
Correct answer: The design maximum fill height or overflow level
API 653 requires the tank to be hydrostatically tested by filling to the design maximum fill height or to the overflow level, whichever is lower.
Question 7: Which condition would exempt a repaired tank from a full hydrostatic retest per API 653?
- Repair is limited to the top two shell courses only
- Repair involves only the annular plate with no shell penetrations
- Repair is limited to non-critical non-pressure-retaining components (Correct answer)
- Repair affects less than 10% of shell plate area
Correct answer: Repair is limited to non-critical non-pressure-retaining components
API 653 permits exemption from hydrostatic retesting when repairs are limited to non-pressure-retaining components such as stairways, walkways, or foam chambers.
API 653 Pressure Testing 2
According to API 653, what is the minimum hold time for a hydrostatic test on a reconstructed tank before inspection begins?