456A Weld Quality Inspection, Testing & Occupational Safety 3

Question 1

What is the '10% RT' inspection requirement for pipeline girth welds under CAN/CSA Z662 and how are the welds selected?

Accepted Answer

10% of all girth welds by a specific welder must be radiographically tested; if defects exceed limits, additional welds by that welder are tested (100% if rejection rate is high)

Answer

CAN/CSA Z662 requires a minimum of 10% of each welder's girth welds to be RT-inspected. Selection includes welds at highest-consequence locations (road crossings, water crossings, etc.) plus random selection. If defect rates are high, the inspection percentage escalates toward 100%. This per-welder tracking ensures that welder performance is monitored and poor-quality welding is caught early.

Question 2

What is 'time-of-flight diffraction' (TOFD) ultrasonic testing and what is its primary advantage?

Accepted Answer

Uses the diffracted signals from defect tips (rather than reflection) to accurately measure defect height/depth; provides more accurate sizing of planar defects than conventional UT reflection techniques

Answer

TOFD uses two probes (transmitter and receiver) placed on either side of the weld. Instead of measuring reflected amplitude, it measures the time of flight of diffracted signals from defect tips. This provides very accurate defect height sizing (important for fracture mechanics fitness-for-service assessments). TOFD is accepted by CSA Z662 and offshore codes for pipeline girth weld inspection in combination with PAUT.

Question 3

What is a 'fitness-for-service' (FFS) assessment under API 579 / CSA Z662 Annex K and when is it applied to welded structures?

Accepted Answer

An engineering analysis that evaluates whether a component with known defects or damage can continue in safe service, possibly with reduced pressure rating or operating limits, rather than requiring immediate repair

Answer

Fitness-for-service (FFS) assessment is applied when inspection reveals defects exceeding the original code acceptance criteria. Instead of automatic rejection, a fracture mechanics-based analysis (using defect dimensions, material toughness, stress levels, and service conditions) determines whether the component can continue in service, possibly with operational restrictions. This avoids costly repairs when remaining life is demonstrably adequate.

Question 4

What is the purpose of 'impact testing' (Charpy V-notch) of weld procedure qualification coupons per CSA W47.1?

Accepted Answer

Verifies that the weld metal and HAZ have adequate toughness (notch ductility) at the specified minimum service temperature to prevent brittle fracture

Answer

Impact testing per CSA W47.1 (and ASME Section IX supplementary essential variables) measures the energy absorbed by the weld metal and HAZ specimens at the specified minimum service temperature. Minimum energy values (e.g., 27 J at -20°C) confirm the procedure produces weld joints with adequate toughness for the design service conditions. Impact qualification is required for most Canadian structural and pressure vessel work.

Question 5

What does the term 'linear indication' mean in dye penetrant or magnetic particle testing?

Accepted Answer

An indication (flaw signal) with a length greater than three times its width; typically indicates a planar defect such as a crack and is generally rejectable

Answer

A linear indication in PT or MT is defined as one where the length is at least three times the width (length ≥ 3W). Linear indications are associated with planar defects (cracks, lack of fusion) and are considered inherently more damaging than rounded indications (pores, inclusions). Most codes treat any linear indication in weld metal as rejectable regardless of size due to the fracture mechanics implications of crack-like defects.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A Weld Quality Inspection, Testing & Occupational Safety 3