pipeline ndt - buax

8/4/2019 Pipeline NDT - Buax

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Corrosion Inspectionby Using NDT Methods

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NON-DESTRUCTIVE EXAMINATION

Nondestructive testing (NDT) is an examination, test, or evaluation performed on any typeof test object without changing or altering that object in any way, in order to determine theabsence or presence of conditions or discontinuities that may have an affect on the

usefulness or serviceability of that object (1)

1. Hellier, CJ,: Handbook of Non Destructive Evaluation, McGraw-Hill, New York (2001) 1.1

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Liquid Penetrant Magnetic Particle Ultrasonic Radiographic

API 5L : The location of the test equipment in the manufacturer's facility shall be at thediscretion of the manufacturer, except that final inspection of weld seams ofcold expanded pipe shall be performed after cold expansion


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DiscontinuitiesDefect on a material during working process of raw material or during its service life

Discontinuities

Inherent Processing Service

wrought cast

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on ingot : porosity, nonmetallic inclusion, pipe on casting : cold crack, hot tear (shrinkage crack), blow hole, porosity on rolling : lamination, seams, stringers on welding : crack, porosity, slag inclusion, lack of penetration, lack of

fusion, undercut on grinding : heat treating crack In service : fatigue


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Object-oriented representation of the probability of detection of acorrosion defect

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General Process Steps for the Main NDE Techniques

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extension of visual inspection; detecting surface-breaking flaws, such as cracks, lapsand folds, on any non-absorbent material's surface.

for surface discontinuities on non porous material

liquid penetration (about 5 10 min. dwell time) into open defect on material surface

procedure : pre-cleaning (solvent clean/vapour degreas / acid/basic clean / paintremoval), drying, penetrant apply (dipping, spraying, flowing or brushing), excesspenetrant removal (water washable, post emulsifying), drying after excess penetrantremoval, developer apply (wet or dry), final interpretation and post-cleaning

application: to detect defect on welding, casting, wrought product

Liquid Penetrant Test (PT)

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Magnetic Particle

electromagnetic examination that used to locate and estimate the size of defects thatare either open to the surface, such as cracks, and delaminations or very nearsubsurface defects such as gas holes and inclusions.

for surface or subsurface discontinuities on ferro-magnetic material

typical detectable defect : porosity, crack, laps, incomplete fusion

magnetization by electric current induction, AC (for surface discontinuities) or DC (forsub surface discontinuities). Magnetic flux will be occurred on material and flux leakageby testing medium (magnetic particle) indicates defect presence

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Radiographic widely used for both welding examinations during construction and corrosion/erosion

detection after facilities are placed in service

This method works based on the differences of radiography film density, made fromsilver-bromide AgBr. Because of radiation from radioactive rays from x-ray generator

or isotope radioactive will make ionization on film layer and developed silver Ag as apermanent shadow, and will make black shadow while processed.

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Test piece

X / rays

Film


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ULTRASONIC

Mechanical wave with frequency > 20kHz generated by probe which is worked bychanging electrical energy to mechanical energy. Properties of material, e.g,density, homogenity, grain size, hardness, etc, will affect the wave reflection. Basedon the reflection, the thickness, defect location and sizes are determined

characterizing material thickness, integrity, or other physical properties by means ofhigh-frequency sound waves

Accuracies as high as 1 micron or 0.0001 inch

usuall o erate at fre uencies between 500 KHz and 100 MHZ

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using piezoelectric transducers to generate bursts of sound waves when excited byelectrical pulses. Lower frequencies for measuring thicker materials

A pulse-echo determines the thickness of a structure by accurately measuring thetime required for a short ultrasonic pulse generated by a transducer to travelthrough the thickness of the material, reflect from the back or inside surface, and be

returned to the transducer. Time interval is only a few microseconds or less the thickness of the test piece (D): D = v.t /2

where : v = the velocity of sound waves in the materialt = the measured round-trip transit time


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ULTRASONIC

performed to take simple thickness readings of material for on stream inspection,perform more sophisticated weld examinations for inherent flaws in the welds

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4 FEATURES IN ULTRASONIC SYSTEM

(1) the ability to provide an image of the interior of a weld,

(2) the ability to quantity incomplete root bead penetration,

(3) automatic high speed collection of data, and(4) data base management capability.

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Modern Microprocessor-controlled Ultrasonic Gage

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Calibration

Surface Roughness of the Test Piece Coupling Technique

Curvature of the Test Piece

FACTORS AFFECTING PERFORMANCE AND ACCURACY

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cous c roper es o e es a er a soun sca er ng, soun

attenuation)

Couplants


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THICKNESS MEASUREMENT

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DEFECT DETECTION

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Defect Detection:

Blow hole

Crack

Inclusion

pipe (wrinkle in ingot) lamination (defect on rolling product)

de-bonding

defect in weld roduct

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These defects can be:

-Inherent defect

-Fabrication defect, or by its application: fatigue, abrasion, corrosion,

impact, etc.

(to be continueed ... Oil & Gas Pipeline ILI tools performance standards)

pipeline ndt - buax

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