API 653 Pressure Testing 3

Question 1

Under API 653, a pneumatic pressure test may be used instead of a hydrostatic test only when:

Accepted Answer

The owner/operator can demonstrate that water would damage the tank or process

Answer

The tank is too large to fill economically

Answer

The tank is scheduled for decommissioning within 5 years

Answer

Shell thickness is greater than 1 inch

Question 2

What is the primary safety hazard associated with pneumatic pressure testing of storage tanks compared to hydrostatic testing?

Accepted Answer

Energy stored in compressed gas greatly exceeds that of liquid under the same pressure

Answer

Higher risk of corrosion on internal surfaces

Answer

Pneumatic tests require higher absolute pressure levels

Answer

Air leaks are harder to detect visually than water leaks

Question 3

According to API 653, what document must the owner/operator prepare before conducting a hydrostatic test on a reconstructed tank?

Accepted Answer

A written test procedure reviewed by the engineer of record

Answer

A material test report (MTR) for all new plate

Answer

An authorized inspection agency approval letter

Answer

An API 510 pressure vessel inspection report

Question 4

When a tank bottom is tested using a vacuum box test per API 653, what is the minimum vacuum level (negative gauge pressure) that must be achieved?

Accepted Answer

3 psi (21 kPa)

Answer

1 psi (7 kPa)

Answer

2 psi (14 kPa)

Answer

5 psi (35 kPa)

Question 5

For a reconstructed tank, API 653 requires the hydrostatic test to be witnessed by:

Accepted Answer

An authorized inspector (AI)

Answer

The tank owner's safety officer only

Answer

A certified weld inspector (CWI)

Answer

The local fire marshal

Question 6

What is the purpose of monitoring foundation settlement during the hydrostatic fill of a repaired or reconstructed tank per API 653?

Accepted Answer

To detect differential settlement that could overstress the bottom and shell

Answer

To confirm that soil compaction meets ASTM standards

Answer

To verify that the anchor bolt torque is adequate

Answer

To measure uplift forces for wind loading calculations

Question 7

Which of the following statements about the API 653 alternative leak test for tank bottoms using MFL (Magnetic Flux Leakage) is correct?

Accepted Answer

MFL is an acceptable method for detecting bottom pitting and wall loss but must be supplemented by a sensitive leak test

Answer

MFL can replace visual inspection but not vacuum box testing

Answer

MFL alone satisfies all API 653 bottom inspection requirements

Answer

MFL is only approved for tanks with bottoms thicker than 0.5 in