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 evaluation

C: 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