NDT Boilermaker Structural Integrity Assessments 4

Question 1

A time-of-flight diffraction (TOFD) scan of a pressure vessel weld shows a lateral wave interruption paired with a backwall echo interruption at the same position.
This combination MOST likely indicates:

Accepted Answer

A through-wall or very deep crack

Answer

A small surface-breaking pit

Answer

Normal weld crown geometry

Answer

Porosity cluster near mid-wall

Question 2

Which failure mode is MOST associated with boiler components operating above the creep threshold temperature for extended periods?

Accepted Answer

Gradual plastic deformation and wall thinning under sustained load

Answer

Brittle fracture at ambient temperature

Answer

Immediate catastrophic rupture upon startup

Answer

Hydrogen embrittlement

Question 3

During a magnetic flux leakage (MFL) inspection of boiler tubes, a strong localized flux leakage signal with a sharp, high-amplitude response MOST likely corresponds to:

Accepted Answer

Pitting or wall-loss defect

Answer

A clean, defect-free tube section

Answer

Scale deposits on the tube ID

Answer

Tube expander marks at the tube sheet

Question 4

When a boiler undergoes alterations, who is responsible under NBIC (National Board Inspection Code) for certifying that the alteration was performed correctly?

Accepted Answer

An authorized 'R' stamp holder

Answer

The original boiler manufacturer

Answer

The jurisdictional authority only

Answer

The plant maintenance supervisor

Question 5

In a boiler structural integrity assessment, 'remaining life' calculations using corrosion rate data require knowledge of:

Accepted Answer

Current minimum measured thickness and allowable minimum thickness

Answer

Original fabrication date and heat number

Answer

Water chemistry pH only

Answer

Combustion gas temperature

Question 6

What is the PRIMARY reason that visual examination of welds should be performed BEFORE other NDT methods during a boiler integrity assessment?

Accepted Answer

Surface conditions and geometry must be confirmed acceptable before applying other methods

Answer

Visual testing is the most sensitive method for subsurface defects

Answer

Code requires visual testing to be the final acceptance step

Answer

Other methods cannot function without prior visual clearance

Question 7

A boilermaker performing a structural integrity assessment finds weld cracks in the heat-affected zone of a P91 chrome-moly steel weld. Which cracking mechanism is MOST likely responsible?

Accepted Answer

Reheat cracking during post-weld heat treatment

Answer

Cold cracking due to hydrogen

Answer

Hot cracking during solidification

Answer

Stress corrosion cracking in service