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Non Destructive Examination
(NDE)
Non Destructive Examination (NDE)
• Non Destructive Examination is the act of evaluating a welded component (or material to be welded) without affecting the serviceability of the part or material.
NDE
• All Welds have flaws.• Another name for a flaw is a discontinuity • Discontinuities are interruptions in the
normal crystalline structure (or grain) of the metal.
• Discontinuities are NOT always defects
NDE
• The purpose of welding inspections is to locate and determine the size of any discontinuities
• Discontinuities that are to large or repeat too often within the weld become defects
• Defects will compromise the welds overall strength
What are some common defects?
• Porosity • Undercutting • Rollover or “Cold Lap”• Slag inclusion • Poor penetration • Voids • Hydrogen Embrittlement
Typical faults in a finished weld.
How would you find these faults ?
Non Destructive Examination
NDE
Common methods used in NDE
• Visual Inspection (VT) • Magnetic Particle Inspection (MT)• Liquid (Dye) Penetrant Inspection (PT)• X-Ray inspection (RT) • Ultrasonic testing (UT) • Air or water pressure testing (LT)
Visual Inspection (VT)
• Visual is the most common inspection method
• VT reveals spatter, excessive buildup, incomplete slag removal, cracks, heat distortion, undercutting, & poor penetration
• Typical tools for VT consist of Fillet gauges Magnifying glasses, Flashlights, & Tape measures or calipers.
Visual Inspection (VT)
• Fillet gauges measure – The “Legs”of the weld – Convexity
• (weld rounded outward)
– Concavity• (weld rounded inward)
– Flatness
Magnetic Particle Inspection (MT)
• Magnetic Particle Inspection (commonly referred to as Magnaflux testing) is only effective at checking for flaws located at or near the surface.
• MT uses a metallic power or liquid along with strong magnetic field probes to locate flaws. (Particles will align along voids)
• MT can only be used on materials that can be magnetized
Liquid (Dye) Penetrant Inspection (PT)
• Liquid penetrant inspection uses colored or fluorescent dye to check for surface flaws.
• PT will not show sub-surface flaws.• PT can be used on both metallic and non
metallic surfaces such as ceramic, glass, plastic, and metal.
• PT dose not require the part to be Magnetized.
X-Ray inspection (RT)
• Welds may be checked for internal discontinuities my means of X- Rays
• An X-Ray is a wave of energy that will pass through most materials and develop the negative image of what it passes through on film.
• A Radiograph ( X-Ray picture) is a permanent record of a weld used for quality inspection purposes
• RT inspections can reveal flaws deep within a component
Ultrasonic testing (UT)
• Ultrasonic testing (UT) is a method of determining the size and location of discontinuities within a component using high frequency sound waves.
• Sound waves are sent through a transducer into the material and the shift in time require for their return or echo is plotted.
• Ultrasonic waves will not travel through air therefore flaws will alter the echo pattern.
Air or water pressure testing (LT)
• Pressure testing or leak testing can be performed with either gasses or liquids.
• Voids that allow gasses or liquids to escape from the component can be classified as gross (large) or fine leaks.
• Extremely small gas leaks measured in PPM (parts per million) require a “Mass Spectrometer” to Sniff for tracer gases
Quiz time
• True or False ?
• Dye penetrate inspections can only be used on non magnetic material.
• Answer: False
Quiz time
• True or False ?
• X-Rays can only be used to locate flaws at or near the surface of a weld.
• Answer: False
Quiz time
• True or False ?
• Virtually all welds have flaws.
• Answer: True
Quiz time
• True or False ?
• Magnetic particle testing can only detect flaws at or near the surface.
• Answer: True
Quiz time
• True or False ?
• Magnet particle testing can only be done on materials that can be magnetized.
• Answer: True
Quiz time
• The letters NDE Mean ___________ ? A: nondestructive inspection
B: nondestructive evaluationC: nondisruptive evaluation D: nondestructive examination
Quiz time
• The method most often used to check for leaks as small as one part per million (PPM) from a gas line or cylinder is the _________ Method ? A: hydrostatic
B: mass spectrometer C: soap suds bubble
D: scleroscope
Modern WeldingYork County School of Technology