Chapter 6: Non-Destructive Testing (NDT) & Reporting

---

🔍 6.1 What is Non-Destructive Testing (NDT)?

NDT is the process of testing materials and welds without damaging them, to detect internal and surface defects that may affect structural integrity.

💡 Key Goal: Ensure product quality and safety without altering its usability.

---

🧪 6.2 Types of NDT Methods in Mechanical QA/QC

Method	Full Name	Best For
VT	Visual Testing	Surface cracks, weld finish
PT	Penetrant Testing	Surface-breaking cracks on non-porous materials
MT	Magnetic Particle Testing	Surface & subsurface flaws in ferromagnetic materials
UT	Ultrasonic Testing	Internal flaws like laminations, voids
RT	Radiographic Testing	Internal cracks, porosity using X-ray/Gamma rays
Eddy Current	Eddy Current Testing	Conductive material flaws (used in aerospace/piping)

---

📋 6.3 Acceptance Criteria

Acceptance criteria are defined by codes such as:

ASME Section V – Procedure for NDT

ASME Section VIII Div. 1 – Pressure vessel acceptance criteria
API 650 – Storage tank weld acceptance
ISO 9712 – NDT personnel qualification standard

👷 QA/QC engineers must know which test applies and the code-based rejection criteria.

---

🛠 6.4 Practical Use Case: Weld Testing in Storage Tank

🔧 For a welded storage tank (API 650):

First, perform VT: Check for cracks, undercut, porosity on the weld bead

Then, perform MT: Surface & subsurface flaw detection on nozzle welds
If welds are load-bearing or safety-critical, UT or RT is done

---

📑 6.5 NDT Reports & Documentation

Every test performed must be documented.

🧾 A typical NDT report includes:

Project Name & Location

Weld or Part No.
Drawing Reference
NDT Method & Procedure No.
Acceptance Criteria (ASME/API/ISO)
Result: Accept / Reject
Technician Name, Level (as per ISO 9712 or ASNT)
Client/QA/QC Engineer signature

📌 Important: Reports must be traceable with weld maps and heat numbers.

---

🎯 6.6 Certification Levels of NDT Personnel

As per ISO 9712 / ASNT SNT-TC-1A:

Level I: Perform specific calibrations & tests under supervision
Level II: Set up and interpret results

Level III: Responsible for procedure development, training, auditing

---

⚠️ 6.7 Common Welding Defects Found by NDT

Defect	Description
Porosity	Trapped gas pockets inside weld metal
Cracks	Fracture or separation in weld/base metal
Incomplete Fusion	Weld does not fuse to base material properly
Undercut	Reduction in base metal along weld toe
Slag Inclusion	Solidified flux trapped in weld metal

---

🧪 6.8 Real-World Case: Boiler Explosion Due to Missed UT

Incident: In a thermal plant, an economizer tube ruptured.
Finding: Internal crack was not detected as UT was skipped during QA.
Impact:

2 fatalities

Power plant shut down
Contractor was penalized & contract revoked

---

📌 6.9 Summary

NDT is essential for detecting invisible flaws

Test method is chosen based on material, location, and risk
Proper documentation ensures traceability
Certification level of technician is mandatory
Skipping NDT can result in catastrophic failure

Quiz: NDT & Reporting

---

Q1. What is the primary purpose of Non-Destructive Testing (NDT)?
A) To reduce cost
B) To identify surface color
C) To test materials without damaging them
D) To test for weight
🟩 Correct Answer: C

---

Q2. Which NDT method is best suited for detecting surface-breaking flaws in non-porous materials?
A) UT
B) MT
C) PT
D) RT
🟩 Correct Answer: C

---

Q3. Which NDT technique uses sound waves to detect internal flaws?
A) PT
B) UT
C) MT
D) Eddy Current
🟩 Correct Answer: B

---

Q4. What is the main limitation of Magnetic Particle Testing (MT)?
A) Expensive equipment
B) Only works on non-metallic materials
C) Only works on ferromagnetic materials
D) Can’t detect any flaws
🟩 Correct Answer: C

---

Q5. Which standard governs the qualification of NDT personnel?
A) ISO 9001
B) ISO 9712
C) API 1104
D) ASME B31.3
🟩 Correct Answer: B

---

Q6. In Radiographic Testing (RT), which of the following is used?
A) Ultrasonic probe
B) Gamma rays or X-rays
C) Magnetic flux
D) Penetrant dye
🟩 Correct Answer: B

---

Q7. A Level II NDT technician can:
A) Only assist under supervision
B) Perform calibration only
C) Set up and interpret test results
D) Develop new testing codes
🟩 Correct Answer: C

---

Q8. What is typically not included in an NDT report?
A) Drawing Reference
B) Heat number
C) Client’s contact number
D) Acceptance criteria
🟩 Correct Answer: C

---

Q9. Which NDT method is most suitable for internal defect detection in thick welded joints?
A) PT
B) MT
C) UT
D) Visual Inspection
🟩 Correct Answer: C

---

Q10. An incomplete fusion defect is typically found in:
A) Forgings
B) Castings
C) Welds
D) Pipes
🟩 Correct Answer: C