Welding Defects and Prevention
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Questions and Answers

What is the primary reason for incorporating a higher current density to prevent Slag Inclusion?

  • To maintain the optimal angle and speed
  • To increase the travel speed of the weld
  • To prevent overheating of the metal
  • To improve the weld's toughness and strength (correct)

    • What is the main purpose of Non-Destructive Testing (NDT) in welding?

  • To observe discontinuities without damaging the weld (correct)
  • To detect only minor defects in the weld
  • To test the finished project to its limits
  • To identify the type of metal used in the weld

    • What is the primary cause of Incomplete Fusion in welding?

  • Incorrect electrode size
  • Low heat input and wrong angles (correct)
  • Poor pre-cleaning and low current density
  • Fast feed speed and high travel speed

    • What is the purpose of Visual Inspection in Non-Destructive Testing (NDT)?

    <p>To observe discontinuities in the weld</p> Signup and view all the answers

    What is the main cause of Whiskers in welding?

    <p>Fast feed speed and high travel speed</p> Signup and view all the answers

    What is the purpose of Destructive Testing in welding?

    <p>To test the finished project to its limits</p> Signup and view all the answers

    What is the main purpose of snipping the electrode before welding to prevent Whiskers?

    <p>To remove electrode remnants from the weld joint</p> Signup and view all the answers

    What is the primary limitation of Magnetic Particle Testing?

    <p>Removal of magnetic particles is required after testing</p> Signup and view all the answers

    What is the main cause of Necklace Cracking in electron beam welding?

    <p>Specific metals and improper technique</p> Signup and view all the answers

    What is the main advantage of Computerized Ferrous Wire Rope Testing over Traditional methods?

    <p>It provides detailed analysis of wire integrity</p> Signup and view all the answers

    What is the primary concern with Radiography Inspection?

    <p>It poses a radiation hazard</p> Signup and view all the answers

    What is the primary limitation of Eddy Current Inspection?

    <p>It is limited to near-surface flaws</p> Signup and view all the answers

    What is the main advantage of ACPD Inspection?

    <p>It provides accurate measurement of crack depth on flat surfaces</p> Signup and view all the answers

    What is the primary requirement for Magnetic Particle Testing?

    <p>A clean surface</p> Signup and view all the answers

    What is the main advantage of Computerized Ferrous Wire Rope Testing over Visual Inspection?

    <p>It offers detailed analysis of wire integrity</p> Signup and view all the answers

    What is the primary purpose of ensuring the integrity and safety of underwater structures and equipment?

    <p>To ensure the integrity and safety of underwater structures and equipment</p> Signup and view all the answers

    What is the primary limitation of Visual Inspection?

    <p>It is subjective and prone to human error</p> Signup and view all the answers

    What is a limitation of visual inspection in non-destructive testing?

    <p>It is highly dependent on human factor</p> Signup and view all the answers

    What is the function of ultrasonic thickness gauging in non-destructive testing?

    <p>To detect, locate, and evaluate defects using sound propagation</p> Signup and view all the answers

    What is the mechanism of the dye penetrant test in non-destructive testing?

    <p>Uses capillary action to reveal surface discontinuities with a dye</p> Signup and view all the answers

    What is the purpose of the surface preparation step in the dye penetrant test?

    <p>To clean the surface of any contaminants</p> Signup and view all the answers

    What is the frequency of the special survey in non-destructive testing?

    <p>Every 3 to 5 years</p> Signup and view all the answers

    What is the purpose of cathodic protection in coatings?

    <p>To replace electrons in the corrosion process</p> Signup and view all the answers

    What is the primary advantage of visual inspection in non-destructive testing?

    <p>It has wide applicability and no significant equipment is required</p> Signup and view all the answers

    Study Notes

    Multilayer Coatings

    • Most common form: FBE primer + polyurethane foam + HDPE
    • Prevents hydrate sheath formation and wax deposition in cold seawater
    • Syntactic material: hollow glass microspheres in a polymer matrix

    Cathodic Protection (CP)

    • Stabilizes metal by replacing electrons in the corrosion process

    Non-Destructive Testing (NDT)

    Introduction

    • Ensures integrity and safety of underwater structures and equipment
    • Techniques: Visual Inspection, NDT, and Destructive Testing

    Classification Society Requirements

    • Annual Survey: Focuses on visual inspection
    • Special Survey: Includes mandatory NDT at selected locations, conducted every 3 to 5 years

    Inspection Methods

    Visual Inspection

    • Ranges from manual examination to sophisticated TV monitoring systems
    • Pros: Wide applicability, no significant equipment required
    • Cons: Highly dependent on human factor, reliability can be compromised by non-defect marks

    Ultrasonic Thickness Gauging

    • Uses sound propagation to detect, locate, and evaluate defects
    • Pros: Effective for a wide range of materials, can detect internal defects
    • Cons: Ineffective for thin materials, geometric complexity can lead to spurious signals

    Dye Penetrant Test

    • Uses capillary action to reveal surface discontinuities with a dye
    • Pros: High sensitivity to small discontinuities, few material limitations, rapid inspection of large areas
    • Cons: Only detects surface-breaking defects, pre-cleaning is critical

    Magnetic Particle Testing

    • Identifies defects by applying magnetic particles on a magnetized test object
    • Pros: Sensitive to fine surface flaws, can detect subsurface defects to some extent
    • Cons: Removal of magnetic particles required after testing, magnetic field orientation and strength critical for detection accuracy

    Ferrous Wire Rope Testing

    • Types: Traditional and computerized methods for detecting external and internal wire breakages
    • Pros: Computerized testing offers detailed analysis of wire integrity
    • Cons: Traditional methods are slow and laborious

    Radiography Inspection

    • Uses X-rays or gamma rays for internal defect detection based on radiation absorption variations
    • Pros: Comprehensive internal examination, suitable for a wide range of materials and defect types
    • Cons: High operational costs, radiation hazard

    Eddy Current Inspection

    • Detects defects by inducing and monitoring changes in eddy current flow
    • Pros: Portable and lightweight equipment, immediate assessment of crack depth and length
    • Cons: Limited to near-surface flaws, requires calibration prior to inspection

    Alternating Current Potential Difference (ACPD) Inspection

    • Assesses the depth of surface-breaking defects through potential difference measurements
    • Pros: Accurate measurement of crack depth on flat surfaces, can be used to monitor crack depth during service life
    • Cons: Requires surface cleaning before testing, complex geometries can lead to false indications

    ROV System Components

    • Control unit, manipulator arm, cable
    • Launch & recovery unit, garage
    • Ongoing issues with failures and wear

    Internal Welding Defects

    Slag Inclusion

    • Description: Slag in the weld metal, compromising toughness
    • Causes: Incorrect angle and speed, poor pre-cleaning, low current density
    • Prevention: Higher current density, optimal angle and speed, consistent cleaning

    Incomplete Fusion

    • Description: Poor welding leading to pre-solidified gaps
    • Causes: Low heat input, wrong angles, large weld pool
    • Prevention: Higher current, slower travel, correct positions

    Incomplete Penetration

    • Description: Gaps in butt welding joints
    • Causes: Incorrect technique, wrong electrode size, low deposition rate
    • Prevention: Correct technique, higher deposition rate, proper electrode size

    Other Welding Defects

    Whiskers

    • Description: Electrode remnants on the weld joint's root side
    • Causes: Fast feed speed, high travel speed
    • Prevention: Snip electrode before welding, reduce feed and travel speed

    Necklace Cracking

    • Description: Incomplete penetration in electron beam welding
    • Causes: Specific metals, improper technique, high speed
    • Prevention: Better material selection, constant speed, correct technique

    Detecting Welding Defects

    Non-Destructive Testing (NDT)

    • Observes discontinuities without damage
    • Methods: Visual inspection, liquid penetrants, magnetic particles, eddy currents, ultrasonics, acoustics, radiography

    Destructive Testing

    • Tests finished projects to their limits
    • Methods: Acid etch, guided bend, free bend, back bend, nick break, tensile strength

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    Quiz Team

    Description

    This quiz covers common welding defects such as slag inclusion and incomplete fusion, as well as preventive measures to avoid them. It highlights the importance of proper welding techniques and maintenance for optimal results.

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