Free QC Inspector Practice Test: 15 Sample Questions with Explanations

One of the most common questions we hear from aspiring QC inspectors is: "Where can I find good practice questions?" Reading the codes is essential, but without practicing exam-style questions, you won't know if you can actually apply what you've read.

This article gives you 15 free practice questions across the major QC inspector disciplines — welding and piping, coating, NDT, and static equipment. Each question comes with the correct answer and a detailed explanation. Use this as a quick self-assessment, then head to the SkillJet.co simulator for the full experience.

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Welding & Piping (ASME B31.3 / API 570)

Question 1

A radiograph of a Category B (normal fluid service) butt weld shows scattered porosity with individual indications up to 2 mm diameter. The weld thickness is 10 mm. Per ASME B31.3 Table 341.3.2, is this acceptable?

• A) Yes, all porosity is acceptable in Category B
• B) Yes, if the indications are scattered and individual size ≤ T/3
• C) No, any porosity is rejectable in Category B
• D) No, the maximum individual size is 1.5 mm regardless of thickness

Answer: B — For Category B, rounded indications (porosity) are evaluated per the ASME Section VIII, Division 1, Appendix 4 porosity charts. Individual indication size up to T/3 (3.3 mm for a 10 mm weld) is generally acceptable if the distribution doesn't exceed the chart limits. Scattered porosity within the chart limits is acceptable.

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Question 2

Per API 570, what is the maximum interval for external inspection of a piping system in API 570 Risk Class 1 (high risk)?

• A) 5 years
• B) 10 years
• C) 3 years
• D) Determined by RBI only

Answer: B — API 570 Table 2-1 specifies maximum inspection intervals. For Risk Class 1 (high risk), the maximum external inspection interval is 10 years, though RBI (Risk-Based Inspection) may extend this. The maximum CML (Condition Monitoring Location) thickness measurement interval is 5 years for Class 1.

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Question 3

A welder qualified on a 6G position test on 2-inch Schedule 80 pipe. Per ASME Section IX, what is the maximum pipe diameter this welder is qualified for?

• A) 2 inches only
• B) Up to 4 inches (2× test diameter)
• C) Up to 12 inches (4T rule)
• D) Unlimited diameter

Answer: B — Per ASME Section IX QW-452, a welder tested on a pipe with outside diameter ≥ 2.5 inches is qualified for unlimited diameter. However, for test pipes with OD < 2.5 inches (like 2-inch Schedule 80, OD ≈ 2.375 inches), the qualification is limited to 2× the test diameter (4.75 inches). The exact rule depends on the test coupon OD.

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Question 4

Per ASME B31.3, what is the minimum hydrotest pressure for a piping system designed for 1000 psi at 400°F (carbon steel, no elevation correction needed)?

• A) 1000 psi
• B) 1200 psi
• C) 1500 psi
• D) 1750 psi

Answer: C — ASME B31.3 requires a minimum hydrotest pressure of 1.5 × the design pressure. 1.5 × 1000 = 1500 psi. The test pressure may need adjustment for temperature differences between design and test conditions, but in this case, the minimum is 1500 psi.

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NDT Methods (ASME Section V)

Question 5

Per ASME Section V Article 5, what is the minimum lifting force for an AC electromagnetic yoke used for magnetic particle testing?

• A) 10 N
• B) 20 N
• C) 30 N
• D) 50 N

Answer: C — ASME Section V Article 5 requires a minimum lifting force of 30 newtons (approximately 6.7 pounds) for AC yokes. This must be verified using a test weight before each shift of use.

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Question 6

What is the minimum film density for a radiograph taken with X-ray source per ASME Section V Article 2?

• A) 1.0
• B) 1.5
• C) 1.8
• D) 2.0

Answer: C — For X-ray sources, the minimum film density is 1.8. For gamma-ray sources (Ir-192, Co-60), the minimum is 2.0. The maximum density for both is 4.0. Film density outside these ranges is unacceptable.

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Question 7

Per ASME Section V Article 6, what is the minimum penetrant dwell time for liquid penetrant testing at 20°C (68°F)?

• A) 5 minutes
• B) 10 minutes
• C) 20 minutes
• D) 60 minutes

Answer: B — At temperatures between 10°C and 50°C, the minimum dwell time is typically 10 minutes. For temperatures below 10°C, longer dwell times are required (up to 60 minutes at very low temperatures). The exact dwell time depends on the penetrant type and the defects being sought.

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Question 8

For direct visual testing per ASME Section V Article 7, what is the maximum distance from the inspector's eye to the surface being examined?

• A) 150 mm (6 inches)
• B) 300 mm (12 inches)
• C) 600 mm (24 inches)
• D) 1000 mm (40 inches)

Answer: C — Direct VT must be performed within 600 mm (24 inches) of the surface, at an angle of not less than 30° to the surface. The inspector must have near vision corrected to at least 20/40 (Jaeger J-2).

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Coating Inspection (NACE/AMPP)

Question 9

Per ISO 8501-1, what surface preparation grade corresponds to near-white metal blast cleaning?

• A) Sa 2
• B) Sa 2.5
• C) Sa 3
• D) St 3

Answer: B — Sa 2.5 corresponds to near-white metal blast cleaning (SSPC-SP 10 equivalent). Sa 2 is commercial blast (SSPC-SP 6), Sa 3 is white metal blast (SSPC-SP 5), and St 3 is power tool cleaning to bare metal (SSPC-SP 11).

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Question 10

Coating shall not be applied when the surface temperature is less than how many degrees above the dew point?

• A) 1°C
• B) 3°C
• C) 5°C
• D) 10°C

Answer: B — The general rule is that coating shall not be applied when the surface temperature is less than 3°C (5°F) above the dew point. This prevents moisture condensation on the surface, which would cause adhesion failure and blistering.

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Question 11

A coating has a volume solids content of 60%. If the specified dry film thickness (DFT) is 150 microns, what is the required wet film thickness (WFT)?

• A) 90 microns
• B) 150 microns
• C) 210 microns
• D) 250 microns

Answer: D — WFT = DFT ÷ volume solids = 150 ÷ 0.60 = 250 microns. The wet film thickness must be 250 microns to achieve a dry film of 150 microns at 60% volume solids.

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Static Equipment (API 510)

Question 12

Per API 510, what is the maximum inspection interval for the internal inspection of a pressure vessel in high-risk service (without RBI)?

• A) 5 years
• B) 10 years
• C) 15 years
• D) Determined by the inspector

Answer: B — API 510 Table 2-1 specifies maximum inspection intervals. For high-risk vessels without RBI, the maximum internal inspection interval is 10 years. RBI (Risk-Based Inspection) can extend this to 15 years or more depending on the risk assessment.

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Question 13

A pressure vessel has a measured thickness of 8.0 mm, a corrosion allowance of 2.0 mm, and a minimum required thickness (t-min) of 6.0 mm. What is the remaining life?

• A) 1 year
• B) 2 years
• C) 5 years
• D) Cannot be determined without the corrosion rate

Answer: D — Remaining life = (current thickness − t-min) ÷ corrosion rate. Without knowing the corrosion rate (mm/year), the remaining life cannot be calculated. The corrosion rate is determined from historical thickness measurements over time.

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Client Standards (SAES-W-011)

Question 14

On a Saudi Aramco project, a piping system is designated as critical service. Per SAES-W-011, what is the typical minimum NDE extent for butt welds?

• A) Spot radiography (5%)
• B) Random radiography (10%)
• C) 100% radiography
• D) Visual examination only

Answer: C — SAES-W-011 typically requires 100% radiographic examination of butt welds in critical service, which is significantly stricter than ASME B31.3's spot/random radiography for normal fluid service. The exact extent depends on the line class designation.

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Question 15

Per SAES-W-011, who must approve the welding consumables used on an Aramco project?

• A) The contractor's QA manager
• B) The third-party inspection agency
• C) Saudi Aramco (consumables must be on the approved list)
• D) AWS (American Welding Society)

Answer: C — SAES-W-011 specifies that welding consumables must be from Saudi Aramco's approved consumable list. The inspector must verify that each consumable batch has proper certification and traceability to the approved list. Generic or unapproved brands are not permitted.

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How Did You Score?

• 13–15 correct: You're in strong shape — consider taking the final certification mock exam to confirm your readiness.
• 10–12 correct: You have a solid foundation but need targeted practice. Use the free diagnostic to identify your weak areas.
• Below 10: You need structured study. Start by reading the relevant codes (ASME B31.3, API 570, ASME Section V) and use the SkillJet.co simulator to build your knowledge systematically.

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Next Steps

These 15 questions are just a sample. The SkillJet.co QC simulator includes hundreds of scenario-based questions across all six disciplines — welding and piping, coating and painting, NDT, static equipment, E&I, and civil and structural. Each question comes with:

• Detailed explanations referencing the specific code clause
• A code reference drawer that shows the actual acceptance criteria
• Domain-level analytics to identify your weak areas
• A final certification mock exam that mirrors real exam conditions

Start your free diagnostic today — no credit card required. When you're ready for the full experience, choose the track that matches your certification goal and start practicing toward your certification.