API 653 Tank Inspection, NDE & Testing 5

Question 1

According to API 653, a tank that has experienced a significant leak must undergo what type of inspection before being returned to service?

Accepted Answer

Internal inspection with floor scanning and full NDE of affected areas

Answer

A tank that has leaked must undergo an internal inspection including floor scanning and NDE of affected areas to identify the cause and extent of damage before returning to service.

Question 2

When performing vacuum box testing on a tank floor weld, the vacuum pressure typically applied is:

Accepted Answer

5-6 psi

Answer

API 650 and API 653 specify that vacuum box tests are performed at a minimum vacuum of 3-4 psi (approximately 21-28 kPa), but 5-6 psi is the typical working range used in practice.

Question 3

What is the primary limitation of using eddy current testing (ECT) for inspecting aboveground storage tank floors?

Accepted Answer

ECT cannot detect corrosion on the underside (soil side) of floor plates

Answer

Conventional eddy current testing is limited to near-surface detection on the side being scanned and has poor sensitivity for soil-side corrosion beneath the floor plate.

Question 4

An API 653 inspector is evaluating a tank that shows uniform shell corrosion. The corrosion rate is calculated as 0.010 in/yr and the current measured thickness is 0.280 in with a minimum required thickness of 0.210 in. What is the remaining life?

Accepted Answer

7 years

Answer

Remaining life = (current thickness – minimum required thickness) / corrosion rate = (0.280 – 0.210) / 0.010 = 7.0 years.

Question 5

Which of the following is a key advantage of phased array ultrasonic testing (PAUT) over conventional single-element UT for tank weld examination?

Accepted Answer

PAUT can electronically steer and focus the beam, providing greater coverage with fewer probe positions

Answer

PAUT uses multiple elements and electronic beam steering/focusing, allowing comprehensive weld coverage with fewer scan passes and improved defect characterization compared to conventional UT.

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

API 653 Tank Inspection, NDE & Testing 5