API 653 Welding & Metallurgy 2

Question 1

Which weld discontinuity is most likely to cause a stress concentration leading to fatigue cracking in a storage tank shell?

Accepted Answer

Undercut

Answer

Undercut creates a sharp notch at the weld toe that acts as a stress concentrator, making it particularly detrimental under cyclic loading.

Question 2

According to API 653, what is the minimum preheat temperature required when welding on a tank shell plate with carbon equivalent (CE) greater than 0.43?

Accepted Answer

150°F (65°C)

Answer

API 653 references ASME Section IX and AWS D1.1 requirements, which generally specify 150°F (65°C) preheat for higher carbon equivalent steels to prevent hydrogen-induced cracking.

Question 3

What type of weld joint is typically used for attaching nozzle reinforcing pads to an API 653 tank shell?

Accepted Answer

Fillet weld on both sides

Answer

Reinforcing pads are typically attached with continuous fillet welds on both the inside and outside edges to ensure full sealing and structural attachment.

Question 4

In the context of API 653 tank repairs, what is 'hydrogen-induced cracking' (HIC) primarily associated with?

Accepted Answer

Atomic hydrogen diffusing into steel during welding

Answer

HIC occurs when atomic hydrogen generated during welding diffuses into the steel and recombines at discontinuities, creating internal pressure that leads to cracking.

Question 5

Which nondestructive testing method is most effective for detecting planar defects (cracks) oriented parallel to the surface in a tank shell weld?

Accepted Answer

Ultrasonic testing (UT)

Answer

UT using angle beam transducers can detect planar defects parallel to the surface that RT may miss because radiation passes through them without significant attenuation.

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

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

API 653 Welding & Metallurgy 2