ndt prsentation

8/16/2019 Ndt prsentation

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Non Destructive Testing

Tony K P


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Visual Inspection

Most basic andcommon inspectionmethod.

Tools includefberscopes,

borescopes,magniying glasses andmirrors.

!obotic cra"lers permitobservation in ha#ardousor tight areas, such as air

ducts, reactors, pipelines.

Portable videoinspection unit "ith

#oom allo"s inspection

o large tan$s andvessels, railroad tan$cars, se"er lines.


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Visual Inspection %undamentals

• Visual Testing is used to determine thequantity, size, surface nish, shape,colour, function, leakage, and surface

discontinuities

• &uccessul results depend on – Trained operators

– 'leanliness and condition o the test ob(ect

– )uality o the optical instrument

– Proper illumination o the test part


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Visual Inspection *+asic Principle

• Illumination o Test specimen "ithlight, usually in the visible region.

• The specimen is then eamined "itheye or by light sensitive devices – Physical measurements

– Visual appearance and colour


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Visual Inspection -pplications

1. 'hec$ing o the surace condition othe component.

2. 'hec$ing o alignment o matingsuraces.

3. 'hec$ing o shape o thecomponent.

4. 'hec$ing or evidence o lea$ing.

5. 'hec$ing or internal side deects


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%re0uently inspected items6-pplications7

1. Pumps• Pump impellers 6bending through erosion

corrosion, "ear and atigue7

• casings, bearings, seals and gas$ets

2. Valves• 8all thinning due to corrosion and erosion

• Valve seats, seals, gas$ets 6"ear, creep

and hardening73. +olting

• +olt ailure6improper tor0ue, "rongmaterials o construction and corrosion7


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4. 'astings•

&urace discontinuities 6adhered sand,scale, crac$s and hot tears7

5. %orgings• Visual inspection o critical components

ollo"ed by /PI

9. trusions

:. Microcircuits

• ;verall 0uality, connection reliability andsolder integrity


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Visual Inspection /imitations

1. 'an detect only surace =a"s

2. ye resolution is "ea$

3. ye atigue

4. scanning the test site "ith ullcoverage "ithout line o sight

5. The inability to provide evaluation"ith a high confdence level


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&election o correct visual techni0ue

• +ased on manufacturing process, "hat defectscould present>

• 8hat "ould the nature of expected defects be>8ould they be visible or hidden>

• 8hat should be used as a basis for determining pass/reject test criteria>

• 'an articial standards be made and usede?ectively>

• 8hat is the smallest defect that can bedetected>

• 8hat is the smallest deect that could possibly

cause part/equipment failure>


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Tools

• The Human Eye

• Optical Aids

– Microscope

– Borescope

– Endoscope

– Flexiscope

– Telescope


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The human ye

• Most sensitive to yello"green light o"avelength 559@ -@

• -de0uate lighting 6


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Visual Perception• Perception is the di?erence bet"een

physical reality and the vie" that "ethin$ "e see. It is ho" an observerBs braininterprets the data it is being given. The

MCllerA/yer illusion demonstrates one othe problems

• Di?erent individuals perceive the samevie" in di?erent "ays and it is importantto $no" "hy and ho" these di?erencesoccur. The di?erence bet"een observersdepends upon preAprogramming o the

brain by training and eperience and the


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Müller-yer illusion


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Deects detected by unaided visualinspection

1. The general condition o component2. The presence or absence o oide flm or

corrosive product on the surace

3. The presence or absence o crac$s,orientation o crac$s and position o crac$srelative to the various #ones

4. &urace porosity, unflled craters, contour o

"eld bead and probable orientation ointerace bet"een used "eld bead andad(oining parent metal

5. Potential sources o mechanical "ea$ness

such as sharp notches or misalignment


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Visual aids* enses, prisms andmirrors

!" #haracteristics of construction enses – - lens is a portion o transparent reracting

medium bounded by t"o spherical

suraces or by one spherical surace and aplane surace.

– /enses usually are made o glass or othertransparent material.

– The centres o curvature o all lenssuraces lie on a single straight line calledthe principal ais o the lens


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Types o /enses


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Magnifcation 6linear magnifcation7o lenses

• Magnifcation is defned as the ratioo the si#e o an image to the si#e othe ob(ect.

• Mathematically, it is given byM &i#e o ImageE&i#e o ob(ect

• The magnifcation is positive "hen

the image is real and inverted and isnegative "hen the image is virtualand erect.


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Prisms• - prism is a transparent reracting body that

is bounded by three rectangular and t"otriangular suraces

• They can be used to deviate a ray o light to

disperse "hite light into visible spectrum orto erect an inverted image as is in+inoculars and Pro(ectors

• In periscope, prism is an important optical

component used to guide the path o light tosee an ob(ect over the surace or "hich theobserver is "ithin the sea as in submarines


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Mirrors

• - surace that re=ects most o thelight alling on it is called a mirror. -plane mirror is a =at and shining

surace – plane mirror

– &pherical mirrors

–

'oncave mirror – 'onve mirror


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Mirrors as optical tools

• -n essential tool or visualeamination is a mirror.

• Mirrors are available in all si#es and

shapes, "ith and "ithout lights.

• They are available "ith longetensions, s"ivel heads, and

remotely actuated heads


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Inspection Mirrors


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Microscope


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Microscope

• Magnifcation M 1@E 8here is the ocal length o the lens and

1@ is a constant that represent theaverage minimum distance at "hichob(ects can be distinctly seen byunaided eye

• The practical range o the magniying

po"er is 1@F to 2@@@F• %ield vie" and depth o feld


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+orescope


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inspection.

'ourtesy o ITIEInstrument Technology, Inc


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+orescope•

To inspect the inside o a narro"tube, bore or chamber

•+orescopes are manuactured in – !igid

– tended

– %leible

– Micro design


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• Main optical components

1. ;b(ective lens systemo /ocated at the end o borescope and it

orms primary image o an ob(ect on the

bac$ o the lens2. !elay lens system

o !eorm the primary image every e"inches along the length o borescope

3. The eyepieceo nables the human eye to see the fnal

image ormed


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Total +orescope magnifcation Mb

• Total +orescope magnifcation Mb

Mb 6Mo 76Mr 76Me 7

Mo magnifcation o ob(ective lens

Mr magnifcation o relay lens, usually 1Me magnifcation o eyepiece


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ndoscope


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endoscope

• ;b(ects are constantly in ocus romabout 4 mm to infnity

• Various vie"ing angles


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%leiscope


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=eiscope

• Provide sharp and clear images oparts and interior suraces

• !emote end tip de=ecion


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Telescope

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