NDT Material Properties & Inspection Standards 4

Question 1

What is the significance of the 'nil-ductility transition (NDT) temperature' in boiler plate steels?

Accepted Answer

Temperature below which steel fractures with essentially no plastic deformation

Answer

Temperature at which the material begins to oxidize rapidly

Answer

Temperature above which creep deformation becomes significant

Answer

Temperature at which the steel reaches maximum tensile strength

Question 2

In ultrasonic thickness testing of a boiler tube, a technician measures a wall thickness significantly below the design minimum. What action should follow?

Accepted Answer

Mark the location and report it for engineering evaluation and potential replacement

Answer

Continue operation until the next scheduled shutdown

Answer

Apply an epoxy patch to restore wall thickness

Answer

Increase system pressure to test the tube's integrity

Question 3

What material property is described by the area under a stress-strain curve up to the point of fracture?

Accepted Answer

Toughness

Answer

Hardness

Answer

Stiffness

Answer

Yield strength

Question 4

Which ASTM standard covers the standard practice for liquid penetrant examination?

Accepted Answer

ASTM E165

Answer

ASTM E709

Answer

ASTM E1186

Answer

ASTM E94

Question 5

What effect does post-weld heat treatment (PWHT) have on the residual stresses in a welded boiler component?

Accepted Answer

It reduces residual stresses by allowing stress relaxation at elevated temperature

Answer

It increases residual tensile stresses to improve fatigue life

Answer

It eliminates all weld defects by remelting the weld zone

Answer

It converts residual tensile stresses to compressive stresses through rapid quenching

Question 6

In the context of ASME pressure vessel codes, what does the 'Maximum Allowable Working Pressure' (MAWP) represent?

Accepted Answer

The maximum internal pressure a vessel is designed to safely withstand in service

Answer

The pressure at which a safety valve must open

Answer

The hydrostatic test pressure applied during fabrication

Answer

The minimum design pressure required by code

Question 7

Which type of corrosion mechanism preferentially attacks grain boundaries in a metal microstructure?

Accepted Answer

Intergranular corrosion

Answer

Galvanic corrosion

Answer

Pitting corrosion

Answer

Crevice corrosion