Boilermaker Structural Integrity Assessments Flashcards

Which factor MOST significantly influences the minimum required thickness calculation for a cylindrical boiler shell under internal pressure?

Answer: Inside radius, allowable stress, and joint efficiency

The hoop stress formula t = PR/(SE) shows that inside radius (P), allowable stress (S), and joint efficiency (E) directly determine required wall thickness.

When using eddy current testing to inspect non-ferromagnetic boiler tubes, a phase angle shift of approximately 90° between two indications MOST likely distinguishes:

Answer: Inside diameter (ID) defects from outside diameter (OD) defects

In eddy current tube inspection, the phase angle of the signal response indicates the depth location of the discontinuity, with ID and OD defects typically separated by approximately 90° on the impedance plane.

A fitness-for-service assessment per API 579-1/ASME FFS-1 for a pressure vessel with general metal loss typically uses which Level 1 screening criterion?

Answer: Remaining thickness ratio (RTR) compared to a minimum allowable ratio

API 579 Level 1 FFS assessment for general metal loss uses the remaining thickness ratio (RTR = measured thickness / required thickness) compared to a minimum acceptable ratio.

During a boiler inspection, an inspector identifies hydrogen damage characterized by internal fissures and blistering in the tube wall. What operating condition MOST likely caused this damage?

Answer: Hydrogen sulfide attack at high temperature (high-temperature hydrogen attack)

High-temperature hydrogen attack (HTHA) occurs when atomic hydrogen at elevated temperatures reacts with carbides in steel, forming methane bubbles that cause internal fissuring and decarburization.

In the context of boiler structural integrity, what does 'minimum design metal temperature' (MDMT) define?

Answer: The lowest temperature at which the component can be pressurized without risk of brittle fracture

MDMT is the lowest permissible temperature at which a pressure component may be subjected to full design pressure, below which brittle fracture risk becomes unacceptable.

When ultrasonic testing reveals a planar indication parallel to the fusion line of a boiler weld, this orientation makes the indication MOST significant because:

Answer: It is oriented perpendicular to tensile hoop stresses, maximizing stress intensity

A planar flaw oriented perpendicular to the principal tensile stress (hoop stress in a cylinder) maximizes the stress intensity factor, making it most susceptible to fracture or fatigue crack growth.

A boiler inspector finds that a longitudinal seam weld in a shell has a measured misalignment (hi-lo) exceeding code limits. What is the PRIMARY structural concern with excessive weld misalignment?

Answer: Secondary bending stresses are induced at the offset, reducing fatigue life

Weld misalignment introduces secondary bending stresses at the offset location due to eccentricity under internal pressure loading, which can significantly reduce cyclic fatigue life.