Overview of NDT

Ch 6 1

Prepared byDr. Hassan Shaaban

Emeritus Professor of Metallurgy, AEAAWS Certified Welding Engineer

Overview ofNondestructive Testing Techniques

Training program onCERTIFIED WELDING INSPECTOR

(CWI)

Ch 6 2

Introduction Oil& Gas industry is one of the most Strategic industries in the world

Oil& Gas industry includes exploration, extraction, refining, transporting

In all stages of the industry a highly strict and firm Inspection & Testing Techniques are required

Prepared byProfessor Dr. Hassan Shaaban

Ch 6 3

Overview of Conventional NDT Methods

Visual Testing (VT) Penetrant Test (PT) Magnetic Particle

(MT) Ultrasonic (UT) Radiographic Testing

(RT) Eddy Current (ET) Acoustic Emission

(AE) Leak Testing (LT)

Prepared byProfessor Dr. Hassan Shaaban

Ch 6 4


Main Divisions of NDT Techniques

Ch 6 5


Summery of Surface Inspection Techniques

Ch 6 6

Prepared byDr. Hassan Shaaban 6

Volumetric Techniques

Ch 6 7


Introduction to Visual Testing (VT)

The inspector using his eyes to look for defects.

May also use special tools such as magnifying glasses, mirrors, or Borescopes.

Visual examiners follow procedures that range from simple to very complex.

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Applications of (VT)Applications Surface discontinuities only Cracks, porosity, slag, misalignment, warpage, incorrect size or number.

Comments Should always be the first method applied.

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Advantages& Limitations of (VT)

Advantages Inexpensive; fast; simple; apply during processing. Can eliminate need for other methods.

LimitationsSurface only; variable and poor resolution; eye fatigue; distractions. Need good illumination.

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Liquid Penetrant Inspection

1. Surface Preparation

2. Penetrant Application

3. Penetrant Dwell

4. Excess Penetrant Removal

5. Developer Application

6. Indication Development

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Applications of (PT)

Applications Surface discontinuities:

Cracks, porosity, seams, laps, leaks.

Comments Messy; need good ventilation.

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Advantages& Limitations of (PT) Advantagesinexpensive; easy to apply; more sensitive than visual alone; use on most materials; rapid; portable.

LimitationsSurface only; not useful on hot, dirty, painted, or very rough surfaces. Requires some technique.

Ch 6 13


Introduction to Magnetic Particle (MT)

Magnetic particle Test (MT) is dependant on exciting a magnetic field in and around the test piece

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Basic Principles of Magnetic Particle (MT)

When a bar magnet is broken in the center of its length, two complete bar magnets will result.

If the magnet is just cracked but not broken completely in two, a north and south pole will form at each edge of the crack.

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Basic Principles cont’

If iron particles are sprinkled on a cracked magnet, the particles will be attracted to the poles at the edges of the crack.

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Applications of (MT)

Applications Surface and near surface discontinuities: Cracks, voids, porosity, inclusions, seams, laps.

Comments Messy. Can cause defects.

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Advantages& Limitationsof (MT)

AdvantagesLow cost; fast; more sensitive to tight cracks than PT; can do near subsurface; portable.

LimitationsMaterial must be ferromagnetic; surface must be clean; part may be demagnetized; alignment of field is important. Requires operator technique.

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Ultrasonic Testing (UT) Ultrasonic Testing (UT) uses piezoelectric Crystals to produce high frequency sound energy to conduct examinations and make measurements.

Ultrasonic inspection can be used for: flaw detection/evaluation,

dimensional measurements,

material characterization, and more.

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Applications of (UT)

Applications Surface and deep subsurface discontinuities: Cracks, laminations, porosity, lack of fusion, inclusions, thickness.

Comments Need good

standards. Frequently used method.

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Advantages& Limitationsof (UT)

AdvantagesRapid if automated but manual is slow; applicable to very thick specimens; can give location and size of discontinuity; good sensitivity; inspect from one side; portable.

Limitations Couplant required; thin

complex shapes are difficult; orientation of discontinuity important; very operator-dependent.

Ch 6 21


Introduction to Radiographic Testing (RT)

This method uses X or Gamma radiation using a radiographic Film as a recording medium.

In order to get maximum sensitivity the defect must be imparallel to the radiation beam.

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Applications of (RT)

Applications Subsurface

discontinuities: Cracks, voids,

inclusions, thickness variation, lack of fusion, incomplete penetration, corrosion, missing components.

Comments One of the most

frequently used methods.Industrial X-Ray Tube

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Advantages& Limitationsof (RT)

Advantages Easily understood

permanent record; usually moderate cost; can be portable; applicable to a wide range of materials.

LimitationsCannot detect laminations; radiation hazard and regulations; access to both sides can be high cost; requires trained operators.

Radiation

Sample

Front screen

Film

Back screen

Ch 6 24

Prepared byDr. Hassan Shaaban 24

Eddy Current Inspection (ECT)

Eddy current inspection is one of several NDT methods that use the principal of “electromagnetism” as the basis for conducting examinations.

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Applications of ECT

Eddy currents can be used for:Crack detection

Material thickness measurements

Coating thickness measurements

Thin tube inspection

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Applications of (ECT)Cont’

Applications Surface and near surface

discontinuities: Seams, composition, thickness, eccentricity, surface condition.

Comments Requires good standards.

Ch 6 27


Advantages& Limitationsof (ECT)

Advantages Extremely rapid; can be

automated; very sensitive; surface contact not necessary; permanent record.

LimitationsConductive materials only; difficult interpretation sometimes, may require special equipment; sensitive to geometry.

Ch 6 28


Acoustic Emission Testing (AET)

Acoustic Emission differs than other techniques in two regards. 1.AET simply listens for the energy released by the object.

2.AET deals with dynamic processes (Leaks), or changes (Phase Change), in a material.

Ch 6 29


Applications of AET

Applications Surface and subsurface discontinuities:

Crack initiation and growth, leaks, phase changes.

detecting and locating faults in pressure vessels or leakage in storage tanks or pipe systems,

monitoring welding applications

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Advantages& Limitations of (AET)

Advantages: Remote and continuous

surveillance, location, severity, permanent record. Tests an entire vessel or system.

Limitations:Contact with system; may

need many contact points; complex interpretation; system must be stressed; usually expensive; some systems are too complex.

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Introduction to Leak Testing

Leakage occurs through a leak (passage) when there is a pressure differential between two sides of a leak.

Leaks can be detected by using electronic listening devices, pressure gauge measurements, liquid and gas Penetrant techniques.

Ch 6 32


Applicationsof (LT)

Applications Leaks in systems or subassemblies.

It includes hydraulic and hydrostatic tests

Hydrostatic tests can produce damage.

Comments Usually the last testing done,

Thin Film Bubble Leak Testing

Overview of NDT

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