Chapter 15: Welding Inspection & Non-Destructive Testing (NDT)

 

Chapter 15: Welding Inspection & Non-Destructive Testing (NDT)

Essential for Mechanical QA/QC Engineers, Fabrication Inspectors, Site Engineers


🔧 1. Importance of Welding Inspection

Welding is a critical joint process in mechanical structures, pipelines, pressure vessels, etc.
Improper welding can cause:

Cracks, porosity, weak joints

Catastrophic failures
Rework and financial loss
🔍 Inspection ensures:
Structural integrity
Safety compliance (ASME, API, AWS codes)
Code conformance
Better lifecycle performance

🔩 2. Key Welding Inspection Stages

StageChecks Involved
Pre-weld InspectionMaterial type, electrode type, WPS review
In-processArc length, temperature, technique, cleaning
Post-weldDimensions, defects, NDT testing, reports

📜 3. Welding Procedure Specification (WPS)

WPS is a written, qualified document that provides:

Welding parameters (current, voltage, technique)

Material & filler metal
Position, preheat/postheat temp
Backing, joint design, etc.

📌 PQR (Procedure Qualification Record): Actual test record proving WPS meets code.


📐 4. Visual Inspection (VT)

First line of defense in weld QA.

Checks:

Cracks, undercut, overlap, porosity

Weld bead size, throat thickness
Spatter, arc strike, root fusion

🛠 Tools: Weld gauges, magnifying glass, mirror, flashlight


🧪 5. Non-Destructive Testing (NDT) Techniques

NDT MethodDescriptionApplication
RT (Radiography)X-ray or gamma rays detect internal defectsCritical pressure vessels, pipelines
UT (Ultrasonic Testing)Sound waves detect internal flawsThick welds, castings
MT (Magnetic Particle)Magnetic field highlights surface/subsurface cracksFerrous materials
PT (Penetrant Testing)Dye penetrant shows surface-breaking defectsAll metals (except porous)
ET (Eddy Current)Electromagnetic testing for surface/near-surface flawsAerospace, thin welds

🏗️ 6. Real-World Application Example

Project: Boiler drum in a thermal plant

Welded by semi-automatic process

RT revealed slag inclusion
Section failed hydrotest
Cost of failure: ₹20 lakh (including delay and repair)

🔧 Lesson: Early UT & RT could have avoided total rework.


📋 7. Welding Defects & Causes

DefectCause
PorosityGas entrapment, wet electrodes
UndercutHigh heat, poor technique
Incomplete PenetrationLow current, poor joint prep
Slag InclusionInadequate cleaning, wrong angle

🔒 8. Safety in NDT

RT: Radiation safety, PPE, warning signs

PT/MT: Handle chemicals with gloves, use ventilation
UT: Wear ear protection in high-decibel environments

🧰 9. Field Application Tips

Always verify WPS and welder qualification (as per ASME Sec IX)

Ensure surface cleaning before PT/MT
Use calibrated UT/RT machines
Maintain NDT logs and weld maps
Cross-check repairs before final clearance

🧪 Welding/NDT Reports Must Include:

Welder ID & WPS used

Joint number
Type of test (UT, RT, etc.)
Results and acceptance status
Inspector signature and date

Quiz: Welding Inspection & NDT


Q1. What is the primary purpose of Non-Destructive Testing (NDT)?
A) To destroy the weld sample
B) To clean the surface of metal
C) To inspect for defects without damaging the component
D) To improve welding speed
🟩 Correct Answer: C


Q2. Which NDT method uses X-rays or gamma rays?
A) Ultrasonic Testing
B) Magnetic Particle Testing
C) Radiographic Testing
D) Penetrant Testing
🟩 Correct Answer: C


Q3. What does a WPS (Welding Procedure Specification) provide?
A) Storage location of welding rods
B) Salary structure of welders
C) Approved parameters and process for welding
D) Testing method for final product only
🟩 Correct Answer: C


Q4. Which of the following is not a surface defect?
A) Porosity
B) Undercut
C) Slag inclusion
D) Arc strike
🟩 Correct Answer: C


Q5. Which NDT method is suitable for detecting sub-surface cracks in ferrous materials only?
A) Penetrant Testing
B) Eddy Current Testing
C) Magnetic Particle Testing
D) Ultrasonic Testing
🟩 Correct Answer: C


Q6. A common reason for porosity in a weld is:
A) Low voltage
B) Wet electrode or contamination
C) Overlapping
D) Incorrect NDT method
🟩 Correct Answer: B


Q7. What kind of information does a Radiographic Test Report contain?
A) Welder’s height
B) X-ray images and defect analysis
C) Electrical power used
D) Paint color used
🟩 Correct Answer: B


Q8. What does “PQR” stand for in welding QA?
A) Product Quality Ratio
B) Procedure Qualification Record
C) Professional Quality Report
D) Primary Quality Rank
🟩 Correct Answer: B


Q9. Which method is best for detecting internal flaws in thick welds?
A) Magnetic Particle Test
B) Visual Inspection
C) Ultrasonic Testing
D) Penetrant Testing
🟩 Correct Answer: C


Q10. What is the first step in visual weld inspection?
A) Apply dye penetrant
B) Check calibration
C) Surface cleaning and lighting
D) Turn off welding machine
🟩 Correct Answer: C


homeacademy

Home academy is JK's First e-learning platform started by Er. Afzal Malik For Competitive examination and Academics K12. We have true desire to serve to society by way of making educational content easy . We are expertise in STEM We conduct workshops in schools Deals with Science Engineering Projects . We also Write Thesis for your Research Work in Physics Chemistry Biology Mechanical engineering Robotics Nanotechnology Material Science Industrial Engineering Spectroscopy Automotive technology ,We write Content For Coaching Centers also infohomeacademy786@gmail.com

إرسال تعليق (0)
أحدث أقدم