High Electrical Potential

Electrons

-+

X-rayGenerator orRadioactive

SourceCreates

Radiation

Exposure RecordingDevice

RadiationPenetratethe Sample

0 2 4 6 8 10

Definisi

Non Destructive Test; NDTadalah pengujianmaterial yang dilakukantanpa harus merusakbagian konstruksi(produk, material) atauobyek yang diuji untukmengetahui cacat baikcacat luar maupun cacatdalam.

• Hasil pemeriksaan produk mengenai jeniscacat, bentuk, tempat yang diteliti, keadaanproduk dan lain-lainnya harus dicatat secaratepat, dan langkah selanjutnya bagi produkyang lulus pemeriksaan, tingkat kualitasnyaharus dicatat dan hasil pencatatan tersebutharus diberikan sebagai umpan balik padabagian perencanaan teknik.

• Bagian perencanaan teknik mengadakanpengaturan kualitas menurut data tersebut dandilaksanakan untuk pencegahan cacat-cacat.Untuk memelihara dan menyempurnakan datatersebut agar selalu dapat menyiapkan standarpemeriksaan yang lebih sempurna.

Tujuan dan PerananPengujian

• untuk menjamin mutu (kualitas) dan kepercayaan terhadapkontruksi (produk, material), yaitu dengan caramemisahkan produk yang gagal.

• penekanan biaya dengan mengetahui lebih dulu produkyang cacat, yaitu penerimaan bahan baku dan bahan yangdiproses dari proses awal sampai akhir bahwa produk yangcacat diketahui seawal mungkin.

• penyempurnaan teknik, yaitu menyisihkan produk yangcacat dilakukan lebih awal dan langkah selanjutnya tingkatkualitas dapat dipelihara dengan memeriksa data secarakolektif, sehingga kualitas dan teknik pembuatan dapatdisempurnakan.

Peranan pengujian atau pemeriksaan dapatdikelompokkan menjadi tiga kelas, yaitu pengujianuntuk :

• Keperluan pembuat; untuk menunjang usaha-usahaperbaikan kepercayaan, kualitas produk (material),perbaikan teknik pembuatan, dan pengurangan biayapembuatan.

• Keperluan pemakai; untuk kepastian kualitas saatpembelian, kepastian dan ketahanan kulaitas selamapenggunaan, dan cara untuk memilih pembuat danmembandingkan hasil.

• Keperluan masyarakat; untuk penilaian terhadapkualitas produk (material), jaminan untuk keamananmasyarakat.

Untuk menjamin kualitas dan kepercayaan,pengujian atau pemeriksaan harus dilakukansecara terus menerus sejak dari tahapperencanaan sampai dengan tahap pemakaian.Tahap-tahap yang harus dilakukan antara lain:

• Pengujian atau pemeriksaan untuk penjajagan.

• Pengujian atau pemeriksaan untuk penelitian danpengembangan.

• Disain meliputi:

– pengujian atau pemeriksaan untuk pemilihanbahan

– pengujian atau pemeriksaan untuk pembuat

– pengujian atau pemeriksaan untuk penentuanpersyaratan disain

• Penggunaan meliputi :

• pengujian atau pemeriksaan untukpenerimaan

• pengujian atau pemeriksaan untukperawatan

• Material : pengujian atau pemeriksaan penerimaan.

• Pembuatan meliputi :

• pengujian atau pemeriksaan untuk carapemrosesan

• pengujian atau pemeriksaan untuk pemilihankondisi proses

• pengujian atau pemeriksaan untuk pengawasankualitas

• pengujian atau pemeriksaan untuk prosesproduksi

Persiapan Sebelum Pengujian• Kepastian dari standar yang digunakan.

Di dalam pengujian atau pemeriksaan terdapat bermacam-macam standar dengan spesifikasi yang berbeda-beda.Berhubung dengan hal tersebut, maka sebelum pengujiandilaksanakan harus ditentukan lebih dulu standar yangakan digunakan termasuk tahun penerbitannya.

• Kepastian tentang jadwal dan lingkungan pemeriksaan.Pengujian atau pemeriksaan produk menyesesuaikanjadwal proses produksi yang dibuat agar tidakmenghambat seluruh pekerjaan dengan memperhitungkankemungkinan adanya pekerjaan yang tidak memenuhisyarat yang akan memerlukan waktu tambahan untukmemperbaiki. Supaya tidak mengganggu pelaksanaanpemeriksaan, maka lingkungan pemeriksaan juga harusdipastikan lebih dahulu, agar pemeriksa dapat melakukantugasnya dengan baik dan aman.

• Pemilihan pemeriksa dan alat yang digunakan.Pemeriksaan sangat tergantung dari pemeriksa, metodapemeriksaan, dan alat yang digunakan, oleh karena ituharus didasarkan pada spesifikasi dan standar yang ada.

• Persiapan benda uji.Sebelum melakukan pemeriksaan produk, harusditentukan lebih dahulu cara-cara pengujian yang akandigunakan dengan memperhatikan perencanaan danfungsi produk. Untuk penanganan produk hasilpemeriksaan, perlu dipelajari tentang cacat maupun letakcacat di dalam produk, dan dipersiapkan benda uji sesuaidengan persyaratan yang diperlukan, serta alat uji harusdikalibrasi terlebih dahulu sebelum digunakan.

Persiapan Sebelum Pengujian(lanjutan)

NDT terhadap lasan, padadasarnya memiliki 2 fungsi:

• Quality control, yang memonitor welderdan peralatan, kualitas, dan logam dasaryang dipergunakan.

• Diterima atau diafkir suatu hasil lasanyang disesuaikan dengan fungsinya.

Tujuan utama Inspeksi las melalui NDT adalahkeberadaan diskontinuitas. Sehinggadiskontinuitas tersebut harus dideteksi,diidentifikasi, dicari lokasinya, ukurannyadan orientasinya.

Pertimbangan Pemilihan Metoda NDTpada Struktur Lasan:

• Karakteristik diskontinuitas• Persyaratan mekanika perpatahan• Ukuran komponen• Kemampuan dibawanya peralatan• Kendala-kendala lainnya:

– Jalan masuk ke lokasi inspeksi– Geometri struktur (datar, lengkung, tebal, tipis, dll)– kondisi permukaan (halus, tidak beraturan, dll)– Mode inspeksi (preservice, in-service, kontinyu,

periodik, sesaat)– Lingkungan (tidakj bersahabat, dibawah air, dll)– Waktu yang tersedia untuk inspeksi (cepat, intensif)– kehandalan– Aplikasi gabungan metoda pengujian– Harga

Metoda NDT:

Visual

Five Most Common NDTMethods

• Visual• Liquid Penetrant• Magnetic• Ultrasonic• X-ray

Most basic and commoninspection method.

Tools includefiberscopes,borescopes, magnifyingglasses and mirrors.

Robotic crawlers permitobservation in hazardous ortight areas, such as airducts, reactors, pipelines.

Portable video inspectionunit with zoom allows

inspection of large tanksand vessels, railroad tank

cars, sewer lines.

Visual Inspection

Visual inspection is usefulfor checking the following:

Dimensional accuracy ofweldmentsConformity of welds to sizeand contour requirementsAcceptability of weldappearance with regard tosurface roughness, weldspatter, and cleannessPresence of surface flawssuch as unfilled craters,pockmarks, undercuts,overlaps, and cracks.

• (a) Mirror on stem: may be flat for normal viewor concave for limited magnification.

• (b) Hand magnifying glass (magnificationusually 2–3´).

• (c) Illuminated magnifier; field of view morerestricted than D (magnification 5–10´).

• (d) Inspection glass, usually fitted with a scalefor measurement; the front surface is placed in

• contact with the work (magnification 5–10´).• (e) Borescope or intrascope with built-in

illumination (magnification 2–3´).

• Gage for visual inspection of afillet weld at a 90° intersection.Similar gages can be made forother

• angles. Dimension given ininches

Appearance Standards.

Workmanship standard for visual comparison during inspection ofsingle-V-groove welds and fillet welds. Dimensions given in inches

• A liquid with high surface wetting characteristicsis applied to the surface of the part and allowedtime to seep into surface breaking defects.

• The excess liquid is removed from the surfaceof the part.

• A developer (powder) is applied to pull thetrapped penetrant out the defect and spread iton the surface where it can be seen.

• Visual inspection is the final step in theprocess. The penetrant used is often loadedwith a fluorescent dye and the inspection isdone under UV light to increase testsensitivity.

Liquid Penetrant Inspection

Magnetic Particle Inspection

The part is magnetized. Finely milled iron particles coated with a dyepigment are then applied to the specimen. These particles areattracted to magnetic flux leakage fields and will cluster to form anindication directly over the discontinuity. This indication can bevisually detected under proper lighting conditions.

RadiographyThe radiation used in radiographytesting is a higher energy (shorterwavelength) version of theelectromagnetic waves that wesee as visible light. The radiation cancome from an X-ray generator or aradioactive source.

High Electrical Potential

Electrons

-+

X-ray Generatoror RadioactiveSource Creates

Radiation

Exposure Recording Device

RadiationPenetratethe Sample

Film Radiography

Top view of developed film

X-ray film

The part is placed between theradiation source and a piece of film.The part will stop some of theradiation. Thicker and more densearea will stop more of the radiation.

= more exposure

= less exposure

The film darkness(density) will vary withthe amount of radiationreaching the filmthrough the test object.

Radiographic Images

High frequency sound waves are introduced into amaterial and they are reflected back from surfaces orflaws.

Reflected sound energy is displayed versus time, andinspector can visualize a cross section of the specimenshowing the depth of features that reflect sound.

f

plate

crack

0 2 4 6 8 10

initialpulse

crackecho

back surfaceecho

Oscilloscope, or flawdetector screen

Ultrasonic Inspection (Pulse-Echo)

Sound beam path in a flat testpiece beingultrasonically inspected with a shearwave from an angle-beam transducer,showing the skip distance between thenodes where the beam reflects from thesurfaces

Three positions of the contact type oftransducer along the zigzag scanning pathused during ultrasonic inspection of weldedjoints. The movement of the sound beampath across the weld is shown on a sectiontaken along the centerline of the transduceras it is moved from the far left position inthe scanning path (a), through anintermediate position (b), to the far rightposition (c).

Ultrasonic scanning procedures todetect longitudinal and transversediscontinuities in welds that (a)are not ground flush and (b) areground flush

Ultrasonic scanning procedurefor full-penetration groove weld(a) and double-fillet welds (b) incorner joints

Discontinuity Signals

Transducer scanning positions for distinguishing between weld metal flawsthat are (a) vertically oriented and (b) in an inclined position

Common Application of NDT

• Inspection of Raw Products

• Inspection FollowingSecondary Processing

• In-Services DamageInspection

Inspection of Raw Products

• Forgings,• Castings,• Extrusions,• etc.

• Machining• Welding• Grinding• Heat treating• Plating• etc.

Inspection FollowingSecondary Processing

• Cracking

• Corrosion

• Erosion/Wear

• Heat Damage

• etc.

Inspection ForIn-Service Damage

Power Plant Inspection

Probe

Signals producedby variousamounts ofcorrosionthinning.

Periodically, power plants areshutdown for inspection.Inspectors feed eddy currentprobes into heat exchangertubes to check for corrosiondamage.

Pipe with damage

Wire Rope Inspection

Electromagnetic devicesand visual inspections areused to find broken wiresand other damage to thewire rope that is used inchairlifts, cranes and otherlifting devices.

Storage Tank InspectionRobotic crawlersuse ultrasound toinspect the walls oflarge above groundtanks for signs ofthinning due tocorrosion.

Cameras onlongarticulatingarms are usedto inspectundergroundstorage tanksfor damage.

Aircraft Inspection• Nondestructive testing is used

extensively during themanufacturing of aircraft.

• NDT is also used to find cracksand corrosion damage duringoperation of the aircraft.

• A fatigue crack that started atthe site of a lightning strike isshown below.

Jet Engine Inspection• Aircraft engines are overhauled

after being in service for a periodof time.

• They are completely disassembled,cleaned, inspected and thenreassembled.

• Fluorescent penetrant inspectionis used to check many of the partsfor cracking.

Pressure Vessel InspectionThe failure of a pressure vesselcan result in the rapid release ofa large amount of energy. Toprotect against this dangerousevent, the tanks are inspectedusing radiography andultrasonic testing.

Rail Inspection

Special cars are used toinspect thousands of milesof rail to find cracks thatcould lead to a derailment.

Bridge Inspection• The US has 578,000

highway bridges.

• Corrosion, cracking andother damage can allaffect a bridge’sperformance.

• The collapse of the SilverBridge in 1967 resulted inloss of 47 lives.

• Bridges get a visualinspection about every 2years.

• Some bridges are fittedwith acoustic emissionsensors that “listen” forsounds of cracks growing.

NDT is used to inspect pipelinesto prevent leaks that coulddamage the environment. Visualinspection, radiography andelectromagnetic testing are someof the NDT methods used.

Remote visual inspection usinga robotic crawler.

Radiography of weld joints.

Magnetic flux leakage inspection.This device, known as a pig, isplaced in the pipeline and collectsdata on the condition of the pipe as itis pushed along by whatever is beingtransported.

Pipeline Inspection

Macam-macam Jenis Cacat

Macam-macam Jenis Cacat (lanjutan)

COMPARISON OFVARIOUS NDTMETHODS.

Applications of magnetic particle testing and other methods of testing for surface andsubsurface flaws

• 1. Burst• NDT methods application and limitations• Ultrasonic testing method• Normally used for the detection of internal bursts.• Bursts are definite breaks in the material and resemble a crack, producing a very sharp reflection

on the scope. 273• Ultrasonic testing is capable of detecting varying degrees of burst, a condition not detectable by

other NDT methods.• Nicks, gouges, raised areas, tool tears, foreign material, or gas bubbles on the article may

produce adverse ultrasonic test results.• Eddy current testing method• Not normally used. Testing is restricted to wire, rod, and other articles under 1/4 inch (6.35 mm)

diameter.• Magnetic particle testing method• Usually used on wrought ferromagnetic material in which the burst is open to the surface or has

been exposed to the surface.• Results are limited to surface and near surface evaluation.• Liquid penetrant testing method• Not normally used. When fluorescent penetrant is to be applied to an article previously dye

penetrant tested, all traces of dye penetrant should first be removed by prolonged cleaning inapplicable solvent.

• Radiographic testing method• Not normally used. Such variables as the direction of the burst, close interfaces, wrought material,

discontinuity size, and material thickness restrict the capability of radiography.

• 2. Cold shuts• Liquid penetrant testing method• Normally used to evaluate surface cold shuts in both ferrous and non-ferrous materials.• Indications appear as a smooth, regular continuous or intermittent line.• Certain castings may have surfaces that are blind and from which removal of excess• penetrant may be difficult.• The geometric configuration (recesses, orifices, and flanges) of a casting may permit buildup of

wet developer thereby masking any detection of a discontinuity.• Magnetic particle testing method• Normally used for the evaluation of ferromagnetic materials.• The metallurgical nature of 431 corrosion-resistant steel is such that, in some cases,• magnetic particle testing indications are obtained which do not result from a crack or other

harmful discontinuities. These indications arise from a duplex structure within the material,wherein one portion exhibits strong magnetic retentivity and the other does not.

• Radiographic testing method• Cold shuts are normally detectable by radiography while testing for other casting• discontinuities.• Cold shuts appear as a distinct dark line, or band, of variable length and width, and definite

smooth outline.• The casting configuration may have inaccessible areas that can only be tested by• radiography.• Ultrasonic testing method• Not recommended. Cast structure and article configuration do not, as a general rule, lend

themselves to ultrasonic testing.• Eddy current testing method• Not recommended. Article configuration and inherent variables restrict the use of this• method.

• 3. Grinding cracks• Liquid penetrant testing method• Normally used on both ferrous and non-ferrous materials for the detection of grinding• cracks.• Liquid penetrant indication will appear as irregular, checked, or scattered pattern of fine• lines.• Grinding cracks are the most difficult discontinuity to indicate and require the longest• penetration time.• Articles that have been degreased may still have solvent entrapped in the discontinuity and• should be allowed sufficient time for evaporation prior to the application of the penetrant.• Magnetic particle testing method• Restricted to ferromagnetic materials.• Grinding cracks generally occur at right angles to grinding direction, although in extreme• cases a complete network of cracks may appear, in which case they may be parallel to the• magnetic field.• Magnetic sensitivity decreases as the size of grinding cracks decreases.• Eddy current testing method• Not normally used for detection of grinding cracks. Eddy current equipment has the• capability and can be developed for a specific non-ferrous application.• Ultrasonic testing method• Not normally used for detection of grinding cracks. Other forms of NDT are more• economical, faster, and better adapted to this type of discontinuity than ultrasonics.• Radiographic testing method• Not recommended for detection of grinding cracks. Grinding cracks are too tight and small.• Other NDT methods are more suitable for detection of grinding cracks.

• 4. Heat-affected zone cracking• Magnetic particle testing method• Normally used for ferromagnetic weldments.• Prod burns are very detrimental, especially on highly heat-treated articles. Burns may• contribute to structural failure of article.• Demagnetization of highly heat-treated articles can be very difficult due to metallurgical• structure.• Liquid penetrant testing method• Normally used for non-ferrous weldments• Material that has had its surface obliterated, blurred, or blended due to manufacturing• processes should not be penetrant tested until the smeared surface has been removed.• Liquid penetrant testing after the application of certain types of chemical film coatings may• be invalid due to the covering or filling of the discontinuities.• Radiographic testing method• Not normally used for the detection of heat-affected zone cracking. Discontinuity• orientation and surface origin make other NDT methods more suitable.• Ultrasonic testing method• Used where specialized applications have been developed.• Rigid standards and procedures are required to develop valid tests.• The configuration of the surface roughness (i.e. sharp versus rounded root radii and the• slope condition) are major factors in deflecting the sound beam.• Eddy current testing method• Although not normally used for the detection of heat-affected zone cracking, eddy current• testing equipment has the capability of detecting non-ferrous surface discontinuities.

• 5. Laps and seams• Liquid penetrant testing method• Compatibility with both ferrous and non-ferrous materials makes fluorescent liquid• penetrant the first choice.• Liquid penetrant indications will be circumferential, slightly curved, intermittent or• continuous indication. Laps and seams may occur individually or in clusters.• Foreign material may not only interfere with the penetration of the penetrant into the• discontinuity but may cause an accumulation of penetrant in a non-defective area.• Surface of threads may be smeared due to rolling operation, thereby sealing off laps and• seams.• Fluorescent and dye penetrants are not compatible. Dye penetrants tend to kill the• fluorescent qualities in fluorescent penetrants.• Magnetic particle testing method• Magnetic particle indications of laps and seams generally appear the same as liquid• penetrant indications.• Non-relevant magnetic indications may result from threads.• Questionable magnetic particle indications can be verified by liquid penetrant testing.• Eddy current testing method• Not normally used for detecting laps and seams. Article configuration is the restricting• factor.• Ultrasonic testing method• Not recommended for detecting laps and seams. Thread configurations restrict ultrasonic• capability.• Radiographic testing method• Not recommended for detecting laps and seams. Size and orientation of discontinuities• restricts the capability of radiographic testing.

• 6. Gas porosity• Radiographic testing method• Radiography is the most universally used NDT method for the detection of gas porosity in• weldments.• The radiographic image of a “round” porosity will appear as oval shaped spots with smooth• edges, while “elongated” porosity will appear as oval shaped spots with the major axis• sometimes several times longer than the minor axis.• Foreign material such as loose scale, flux, or splatter will affect validity of test results.• Ultrasonic testing method• Ultrasonic testing equipment is highly sensitive, capable of detecting microseparations.• Established standards should be used if valid test results are to be obtained.• Surface finish and grain size will affect the validity of the test results.• Eddy current testing method• Normally confined to thin-wall welded pipe and tube.• Penetration restricts testing to a depth of not more than one quarter inch.• Liquid penetrant testing method• Normally confined to in-process control of ferrous and non-ferrous weldments.• Liquid penetrant testing, like magnetic particle testing, is restricted to surface evaluation.• Extreme caution must be exercised to prevent any cleaning material, magnetic (iron oxide),• and liquid penetrant materials from becoming entrapped and contaminating the rewelding• operation.• Magnetic particle testing method• Not normally used to detect gas porosity. Only surface porosity would be evident. Near• surface porosity would not be clearly defined since indications are neither strong nor• pronounced.