An Introduction of NDE -- NDT

INTRODUCTION TONON DESTRUCTIVE EXAMINATION

OUTLINE

MATERIAL TESTING

OVERVIEW OF FOUR NDE METHODS Liquid Penetrant Testing (PT)

Magnetic Particle Testing (MT)

Radiography Testing (RT)

Ultrasonic Testing (UT)

APPLICATION OF NDE

Material Testing Material testing is the technology of assessing the soundness and

acceptability of an actual component with or without affecting thefunctional properties of either test specimen or actual job.

MATERIAL TESTING

Destructive Non-destructive

Tensile testing Radiography testing

Compression testing Ultrasonic testing

Impact testing Magnetic particle testing

Fatigue testing Liquid penetrant testing

Creep testing Eddy current testing

Bend testing Acoustic emission testing

Micro/Macro testing Neutron radiography testing

Chemical testing etc Thermography etc

Material TestingMATERIAL TESTING

Destructive Non-destructive

Measure accurate or specific

characteristics of materials by

destroying the specimen

Monitoring and maintaining

material quality, components

reliability & systems safety

without destroying actual job.

UTS Surface & Subsurface flaws

Proof stress Coating & plating thickness

% Elongation Sorting

% Reduction area Velocity & thickness monitor

Youngs modulus Structure and assembly evaluation

Fatigue strength Reliable life assessment etc..

Creep strength

Fatigue properties etc

DEFINITION OF N.D.E.:

NDE is a tool, which uses inspection technology to determinesoundness & measurement of characteristics of the rawmaterial, components, structure & equipments etc. withoutcausing harm to them.

Material Testing

Material Testing

TYPE OF INDICATION: False Indication: Indication, that occurs due to incorrect processing or

incorrect procedure.

Non-relevant Indication: It is an indication, which has no relation tothe discontinuity. i.e. Code has given various sizes of indications whichare not be considered as relevant indication.

Relevant Indication: It is the indication that needs to be evaluated forserviceability and can either be determined as discontinuity or defect.i.e. A indication that may or may not be acceptable by reference codesection.

Material Testing

DISCONTINUITY & DEFECT: Discontinuity: It is any local variation in material continuity which may

not interfere to its intended service life. E.g. Change in geometry,presence of holes, cavities or inclusions.

Defect: When any discontinuity, single or multiple, is of such size,shape, type and location, that it can create a substantial failure ofmaterial in its intended service, is known as DEFECT.

Remember: Every discontinuity is not a defect, Every defect is adiscontinuity.

Methods of N.D.E. Visual Inspection (VT)

Liquid Penetrant Testing (PT)


Radiographic Testing (RT)


Eddy Current Testing (ET)

Leak Testing (LT)

Acoustic Emission Testing (AET)

Infrared Thermal Testing (IRT)

Remote Field Testing (RFT)

Nuclear Radiographic Testing (NRT)

Common Methods used in N.D.E.

Visual Testing (VT)

Liquid Penetrant Testing (PT)


Radiographic Testing (RT)


INTRODUCTION TOLIQUID PENETRANT TESTING

OUTLINE Introduction & Working principle

Basic operation procedure of PT

Materials used in PT

Classification of PT

Application of PT

Types of defects detected by PT

Advantages & Limitations of PT

Code Acceptance criteria

PT in Boiler

LIQUID PENETRANT TESTING (PT)


INTRODUCTION:

PT is a common method used to detect surface breaking flaws.

Flaws are detected by bleed-out of a colored or fluorescent dye fromit.

The technique is based on ability of a liquid to be drawn into a cleansurface breaking flaw by capillary action.

After a period of time called the dwell, excess surface penetrant isremoved and a developer applied. This acts as a blotter.

Visible color contrast penetrants require day-light or hand bulb.

Fluorescent penetrants need to be used in darkened area with anultraviolet "black light".


INTRODUCTION (CONT.):

PT produces a flaw indication that is much larger and easier than flawfor the eye to detect.

PT produces a flaw indication with a high level of contrast between theindication and the background also helping to make the indicationmore easily seen.


WORKING PRINCIPLE:

FLUORESCENT PT

VISIBLE PT

LIQUID PENETRANT TESTING (PT) BASIC OPERATION PROCEDURE OF PT:

Surface preparation (Pre-cleaning): The surface must be free of oil,grease, dust, rust and other contaminants that may prevent penetrantfrom entering flaws. Sometimes, test surface may also requiremachining, sand or grit blasting, grinding, buffing etc.

SOLVENT CLEANING

LIQUID PENETRANT TESTING (PT) BASIC OPERATION PROCEDURE OF PT (CONT.)

Penetrant application: Penetrant can be applied by spraying,brushing, wiping, or dipping the part in a penetrant bath.

DYE APPLICATION BY BRUSHING DYE APPLICATION BY SPRAYING


Penetrant dwell time (PDT): The penetrant is left on the surface for asufficient time to allow penetrant to be drawn into a defect. PDT areas recommended by manufacturers or as per written procedure beingfollowed.

Excess penetrant removal: This step is most delicate. Depending upontype of penetrant used, step may involve cleaning by emulsifier,rinsing with water, solvent remover.

EXCESS PENETRANT REMOVAL BY SOLVENT EXCESS PENETRANT REMOVED

LIQUID PENETRANT TESTING (PT) BASIC OPERATION PROCEDURE OF PT(CONT.)

Developer application: A thin & uniform layer of developer is appliedto drag out penetrant trapped in the flaw. Developer may be appliedby Spraying, dusting, or dipping.

DEVELOPER APPLICATION BY SPRAYING

Slide 17


Developer dwell time (DDT): The developer is left on the surface for asufficient time to allow it to extract the penetrant out from thediscontinuity. It is usually 10 mins as recommended by themanufacturer or written procedure.

Interpretation/Evaluation: After passing developing dwell timeinspection is performed under required lighting conditions.

Post-cleaning: Last step of the inspection process is to clean theresidual penetrant material from the test surface.

EVALUATION

LIQUID PENETRANT TESTING (PT) MATERIALS & EQUIPMENTS USED IN PT:

Cleaner (Solvent remover)

Penetrant (Dye)

Developer

Lint free cotton cloth

Emulsifier (Lipophilic or Hydrophilic)*

Black light (UV light)

Lux meter & UV meter

Thermometer

*Use of Emulsifier depends upon the type of method chosen for PT

CLASSIFICATION OF PT:

A. Based on type of examination techniquea) Visible color contrast method

b) Fluorescent method

B. Based on type of Penetrant removal processa) Solvent removable technique

b) Water washable technique

c) Post emulsifiable technique (Lipophilic)

d) Post emulsifiable technique (Hydrophilic)


LIQUID PENETRANT TESTING (PT)APPLICATION OF PT:

Materials that can be examined with PT:

PT can be applied on all non-porous materials. e.g. Metal, Plastic,Glass, Ceramics etc.

TYPES OF DEFETCS CAN BE DETECTED WITH PT:

Flaws that can be detected by PT:

Only surface flaws can be detected.

Cracks

Porosity

Laps

Seams

Lamination

Cold shuts

LIQUID PENETRANT TESTING (PT)Good PT performance practice!!!

Pre-cleaning: The surface to be examined along with adjacent areasof 25mm (1 inch.) must be free of oil, grease, lint, dirt, rust, spatter,welding flux, scale etc. If required, grinding or buffing needs to bedone other than solvent remover.

Temperature: The temperature of surface to be examined &penetrant material should be within 5 to 52 C inclusive.

Lighting requirement: The visible day light shall be 1000 luxminimum at the surface to be examined. If there is a insufficientlight condition to perform examination, than use 60W bulb from 9inch distance or 100W bulb from 12 inch distance as a thumb rule.

In case, where fluorescent PT is applied, The visible ambient lightshall not be more than 20 lux in the darkened area. The UV lightused shall have 1000 W/cm2 intensity.


ADVANTAGES: Highly sensitive to small surface discontinuities. Can be applied to all metallic and nonmetallic, magnetic and

nonmagnetic, and conductive and nonconductive materials can beinspected.

Large areas and large volumes of parts/materials can be inspectedrapidly and at low cost.

Complex geometric parts are routinely inspected. Indications are produced directly on the surface of the part and

constitute a visual representation of the flaw. Aerosol spray cans make penetrant materials very portable. Penetrant materials and associated equipment are relatively less

costlier.


LIMITATIONS: Only surface breaking defects can be detected. Only materials with a relatively nonporous surface can be

inspected. Pre cleaning is critical since contaminants can mask defects. Metal smearing from machining, grinding, and grit or vapor blasting

must be removed prior to PT. The inspector must have direct access to the surface being

inspected. Surface finish and roughness can affect inspection sensitivity. Multiple process operations must be performed and controlled. Post cleaning of acceptable parts or materials is required. Chemical handling and proper disposal is required.

CODE ACCEPTANCE CRITERIA (ASME SECTION-I, A-270) Evaluation of indications

Only indications with major dimensions greater than 1.5 mm shall beconsidered as relevant.

Any doubtful indication shall be re-examined to confirm whether theyare relevant or not.

Linear indication = l>3w Rounded indication = l3w

Where,l = Length of indication andw = width of indication


CODE ACCEPTANCE CRITERIA (ASME SECTION-I, A-270) (CONT.) Acceptance criteria

All surfaces to be examined shall be free of: Any relevant linear indication Rounded indication more than 5mm dia. Four or more rounded indications in a line separated by 1.5mm or

less distance (edge to edge)


PT IN BOILER: HEADER

Gas cutting/Machining of nozzle hole Fit up lug removal Circumferential welds Nozzle edge preparation Nozzle welding End plate welding Attachment welding Orifice welding Stub to tube welding All welding after PWHT


PT IN BOILER: COIL

Tube bending areas for Squeezing, Swaging (20%) [FOI] Tube to tube welding (25%) Attachment welding

PANEL Tube to tube welding 10% on MPM welding


INTRODUCTION TOMAGNETIC PARTICLE TESTING

OUTLINE Introduction & Working principle

Basic operation procedure

Equipments used in MT

Direction of Magnetic field

Application of MT

Types of defect detected with MT

Pros & Cons of MT

Code Acceptance criteria

MT in Boiler

MAGNETIC PARTICLE TESTING (MT)

MAGNETIC PARTICLE TESTING (MT)INTRODUCTION:

MT is relatively fast & easy to apply, part surface preparation isalso not essential parameter for this method.

MT helps determining the flaws lying near surface also.

MT uses magnetic fields & finely milled iron particles to detectflaws only in ferromagnetic test specimen.

If iron particles are sprinkled on a cracked magnet, the ironparticles will be attracted to end of poles as well as at the edgesof the crack and form a cluster to make the flaw visible.

This cluster of particles is much easier to see than the actualcrack and this is the basis for magnetic particle inspection.


WORKING PRINCIPLE:

BASIC OPERATION PROCEDURE OF MT: Pre-cleaning: It is essential for the particles to have an unimpeded path for migration to

both strong and weak leakage fields alike. The parts surface should be clean and drybefore inspection. Test surface shall be free of external particles like oil, grease, dirt, rustetc.

Checking field adequacy: Pie shaped field indicator, flaw shims or tangential field probe(Gauss meter) shall be used to check proper set up of the equipment.

Magnetizing the component: First step is to magnetize the component to be inspected.This can be accomplished by Prods, Yokes, Coil and conductive cables or Stationary MTmachine. MT can be done with various currents like AC, DC or HWDC.

Application of Iron particles:

After magnetizing the component, the iron particles are spread on the surface to beexamined. This can be accomplished either by Dry particle application or in Wetsuspended form.

The particle will attracted and form a cluster at the flux leakage areas to make avisible indication.

Interpretation/Evaluation:

Evaluation of indication as per applicable code, or standard.

Demagnetization:

Demagnetize the specimen after completing the inspection, if required.


EQUIPMENTS USED IN MT:

Prods

Yoke

Magnetizing coil & conductive cables

Power source

Stationary MT unit

Black light

Lux meter

UV light meter

Dry magnetic particles

Wet magnetic particles

Field indicator (Pie gage)

Flaw shims

Gauss meter (Tangential field probe)


MAGNETIC PARTICLE TESTING (MT)Equipments used in MT:

Portable Equipments

Stationary Equipment

MAGNETIC PARTICLE TESTING (MT)Magnetizing current used in MT:

FOR SKIN EFFECT

& PARTICLE

AGITATION

TO DETECT

DEFECTS LYING

NEAR SURFACE

MAGNETIC PARTICLE TESTING (MT)Magnetic particles:

Magnetic particles are mixture of rounded & slandered particleswith the size of 10 to 200 . It is also available in different colorsto enhance visibility, depending upon metallic background orthe applied contrast.

Classification based on visibility.

Visible (Non-Fluorescent) particles

Fluorescent particles

Classification based on carrier

Dry particle

Wet particle

MAGNETIC PARTICLE TESTING (MT)Magnetic particles:

Wet Magnetic particles(Visible)

Wet Magnetic particles(Fluorescent)

Dry Magnetic particles

Air as Carrier

Bath concentration checking

Liquid as Carrier

MAGNETIC PARTICLE TESTING (MT)Light Meters:

Lux meter (White light) UV Light meter (Black light)

Intensity of the light to be

checked before start of

examination, to verify

adequacy of light.

MAGNETIC PARTICLE TESTING (MT)Field adequacy in MT:

Pie shaped magnetic field indicator Tangential field probe

Artificial flaw shims

MAGNETIC PARTICLE TESTING (MT)DIRECTION OF MAGNETIC FIELD & ORIENTATION OF DEFECTS:

To properly inspect a part for defects, it is important to become familiarwith the different types of magnetic field.

One of the primary requirements for detecting a defect in a ferromagneticmaterial is that the magnetic field induced in the part must intercept thedefect at a 45 to 90 angle. Flaws that are at 90 to the magnetic field willproduce the strongest indications because they disrupt more of themagnet flux.

Therefore, for proper inspection of a component, it is important to be ableto establish a magnetic field in at least two directions.

MAGNETIC PARTICLE TESTING (MT)DIRECTION OF MAGNETIC FIELD:

Two types of magnetic field

A) Circular Magnetic field

A circular magnetic field has magnetic lines of force that runcircumferentially around the perimeter of a part.

Accomplished by passing the current through the solidbar/component.

Also can be produced by passing current through centralconductor in hollow pipe.

HEAD SHOT FOR CIRCULAR MAG. FIELD


Two types of magnetic field (Cont.)

B) Longitudinal Magnetic field

Usually established by placing the part near the inside or a coilsannulus.

This produces magnetic lines of force that are parallel to the long axisof the test part.

LONGITUDINAL MAGNETIC FIELD (COIL SHOT)

Portable

coil

Conductive

cable


Longitudinal Magnetic Particle Testing Equipment (YOKE)

An electromagnetic yoke is a very common piece of equipment that isused to establish a magnetic field.

It is basically made by wrapping an electrical coil around a piece of softferromagnetic steel.

They can be powered with alternating current (AC) from a wall socket orby direct current (DC) from a battery pack.

This type of magnet generates a very strong magnetic field in a local areawhere the poles of the magnet touch the part being inspected.


Circular Magnetic Particle Testing Equipment (PROD)

The current passing between the prods creates a circular magnetic fieldaround the prods that can be used in magnetic particle inspection. Prodsare typically made from copper and have an insulated handle.

If proper contact is not maintained between the prods and the componentsurface, electrical arcing can occur and cause damage to the component.

MAGNETIC PARTICLE TESTING (MT)APPLICATION OF PT:

Materials that can be examined with MT:

MT can be applied on all ferromagnetic materials. e.g. Ferrite, Steel,Nickel, Cobalt alloys etc.

TYPES OF DEFETCS CAN BE DETECTED WITH MT:

Flaws that can be detected by MT:

Surface & near surface flaws can be detected only in ferromagneticmaterial.

Surface & near surface cracks

Undercuts

Lap

Seam

Lamination

ADVANTAGES Can detect both surface and near surface defects.

Can inspect parts with irregular shapes easily.

Pre-cleaning of components is not as critical as it is for some other inspectionmethods. Most contaminants within a flaw will not hinder flaw detectability.

Fast method of inspection and indications are visible directly on the specimensurface.

Considered low cost compared to many other NDT methods.

Is a very portable inspection method especially when used with batterypowered equipment.


LIMITATIONS Cannot inspect non-ferrous materials such as aluminum, magnesium or most

stainless steels.

Inspection of large parts may require use of equipment with special powerrequirements.

Some parts may require removal of coating or plating to achieve desiredinspection sensitivity.

Limited near surface discontinuity detection capabilities. Maximum depthsensitivity is approximately 0.6 (under ideal conditions).

Post cleaning, and post demagnetization is often necessary.

Alignment between magnetic flux and defect is important.


CODE ACCEPTANCE CRITERIA (ASME SECTION-I, A-260) Evaluation of indications

Only indications with major dimensions greater than 1.5 mm shall beconsidered as relevant. Any doubtful indication shall be re-examined to confirm whether

they are relevant or not. Linear indication = l > 3w Rounded indication = l 3wWhere,

l = Length of indication andw = width of indication


CODE ACCEPTANCE CRITERIA (ASME SECTION-I, A-260) (CONT.)

Acceptance criteria All surfaces to be examined shall be free of:

Any relevant linear indication Rounded indication more than 5mm dia. Four or more rounded indications in a line separated by 1.5mm or

less distance (edge to edge)


MT IN BOILER: HEADER

Gas cutting/Machining of nozzle hole Fit up lug removal Circumferential welds Nozzle edge preparation Nozzle welding End plate welding Attachment welding Orifice welding Stub to tube welding All welding after PWHT


MT IN BOILER: COIL

Attachment welding

PANEL 10% on MPM welding. (Being implemented)


INTRODUCTION TORADIOGRAPHY TESTING

OUTLINE Working principle

Radiation sources

Nature of X-rays & Gamma rays

Gamma radiography

X-ray radiography

Film radiography

Radiographic sensitivity

Image Quality Indicators (IQI) or Penetrameters

Examples of welding discontinuities in RT

Radiographic acceptance standards

Safety in radiation

Application of RT

Defects can be detected in RT

Advantages & Limitations of RT

RADIOGRAPHY TESTING (RT)

WORKING PRINCIPLE

The part is placed between the radiation source and a piece of film. Thepart will absorb some of the radiation. Thicker and more dense area willabsorb more of the radiation.

The film darkness (density) will vary with the amount of radiation reachingthe film through the test object.


RADIATION SOURCES

Two of the most commonly used sources of radiation in industrialradiography are x-ray generators and gamma ray sources. Industrialradiography is often subdivided into X-ray Radiography orGamma Radiography, depending on the source of radiation used.


NATURE OF X-RAYS & GAMMA RAYS.

They are form of Electromagnetic radiation

They are extremely short in wavelength, about 1/10,000 of light, or even less.

This feature makes rays able to penetrate in material that absorb or reflect ordinary light.

The only difference in X-ray & Gamma-ray is that, X-rays are emitted from X-ray generator and Gamma rays are emitted from activated radioisotope.


NATURE OF X-RAYS & GAMMA RAYS (CONT.)


GAMMA RADIOGRAPHY

Gamma rays are produced bya radioisotope.

A radioisotope has anunstable nuclei that does nothave enough binding energyto hold the nucleus together.

The spontaneous breakdownof an atomic nucleusresulting in the release ofenergy and matter is knownas radioactive decay.


GAMMA RADIOGRAPHY (CONT.)

Most of the radioactivematerial used in industrialradiography is artificiallyproduced.

This is done by subjectingstable material to a sourceof neutrons in a specialnuclear reactor.

This process is calledactivation.


GAMMA RADIOGRAPHY (CONT.) Unlike X-rays, which are produced by a machine, gamma rays

cannot be turned off. Radioisotopes used for gamma radiographyare encapsulated to prevent leakage of the material.

The radioactive capsule is attached to a cable to form what isoften called a pigtail.

The pigtail has a special connector at the other end that attaches toa drive cable.


GAMMA RADIOGRAPHY (CONT.) A device called a camera is used to store, transport and expose

the pigtail containing the radioactive material. The camera containsshielding material which reduces the radiographers exposure toradiation during use.


GAMMA RADIOGRAPHY (CONT.) A hose-like device called a guide tube is connected to a threaded

hole called an exit port in the camera. The radioactive material will leave and return to the camera

through this opening when performing an exposure.


GAMMA RADIOGRAPHY (CONT.) A drive cable is connected to the

other end of the camera. This cable,controlled by the radiographer, isused to force the radioactivematerial out into the guide tubewhere the gamma rays will passthrough the specimen and exposethe recording device.


X-RAY RADIOGRAPHY Unlike gamma rays, x-rays are produced by an X-ray generator

system. These systems typically include an X-ray tube head, ahigh voltage generator, and a control console.


X-RAY RADIOGRAPHY (CONT.) X-rays are produced by establishing a very high voltage

between two electrodes, called the anode and cathode. To prevent arcing, the anode and cathode are located inside a

vacuum tube, which is protected by a metal housing.


X-RAY RADIOGRAPHY (CONT.) The cathode contains a small

filament much the same as in a lightbulb.

Current is passed through thefilament which heats it. The heatcauses electrons to be stripped off.

The high voltage causes these freeelectrons to be pulled toward atarget material (usually made oftungsten) located in the anode.

The electrons impact against thetarget. This impact causes an energyexchange which causes x-rays to becreated.

High Electrical Potential

Electrons

-+

X-ray Generator

or Radioactive

Source Creates

Radiation

Exposure Recording Device

Radiation

Penetrate

the Sample


RADIATION INTERACTION WITH MATTER:

Radiation absorption or scattering occurs depending upon energy of beam.

Photoelectric absorptionCompton scattering


FILM RADIOGRAPHY One of the most widely used and

oldest imaging mediums in industrialradiography is radiographic film.

Film contains microscopic materialcalled silver bromide.

Once exposed to radiation anddeveloped in a darkroom, silverbromide turns to black metallic silverwhich forms the image.


FILM RADIOGRAPHY (CONT.) Film must be protected from visible light. Light, just like x-rays and

gamma rays, can expose film. Film is loaded in a light proofcassette in a darkroom.

This cassette is then placed on the specimen opposite the source ofradiation. Film is often placed between screens to intensifyradiation.


FILM RADIOGRAPHY (CONT.) In order for the image to be viewed, the film must be developed

in a darkroom. The process is very similar to photographic filmdevelopment.

Film processing can either be performed manually in open tanksor in an automatic processor.


FILM RADIOGRAPHY (CONT.) Once developed, the film is typically referred to as a

radiograph.


RADIOGRAPH SHOWING POROSITIES IN WELDING

RADIOGRAPHY IMAGING TECHNIQUES:Single wall single image (SWSI)


RADIOGRAPHY IMAGING TECHNIQUES:Double wall single image (DWSI)


RADIOGRAPHY IMAGING TECHNIQUES:Double wall double image (DWDI)


RADIOGRAPHIC SENSITIVITY It is the ability of a technique to determine smallest

discontinuity. It is a combination of Radiographic contrast &Radiographic definition. Radiographic contrast is the density difference between two

adjacent areas of the radiograph and is the net effect due to Film contrast & Subject contrast

Radiographic definition refers to the sharpness of the radiographicimage. The causes of radiographic un-sharpness: Geometric un-sharpness (Ug) Movement un-sharpness (Um) Inherent or film un-sharpness (Ui) Scatter and screen un-sharpness (Us)


IMAGE QUALITY INDICATORS (IQI) OR PENETRAMETERS It is used to judge quality of a radiograph and is measured in

terms of radiographic sensitivity. The penetrameter is available in various designs.

e.g. Step type penetrameter Hole-step penetrameter Plate type penetrameter Wire type penetrameter Hole type penetrameter

IQIs should be placed on the source side of radiation, if in case,it is not possible to put it at source side it should be placed filmside of radiation, in such case, letter F should be placed on thefilm.

Wire type IQI should be placed across the weld. Hole type IQI should be placed parallel to the weld & 3mm

apart from the weld edge.



HOLE TYPE PENETRAMETERS

WIRE TYPE PENETRAMETERS

FILM IDENTIFICATION LEAD

LETTERS

LOCATION MARKER:

Location markers are put to ensure total coverage of weld volume and for future traceability.

Location marker shall always be put on job permanently and shall be visible on radiograph.


EXAMPLES OF WELDING DISCONTINUITIES IN RT


RADIOGRAPH SHOWING LACK OF PENETRATION IN WELDING

SOME EXAMPLES OF RADIOGRAPHIC FILMS


RADIOGRAPH SHOWING LACK OF FUSION IN WELDING



RADIOGRAPH SHOWING UNDER CUT IN WELDING



RADIOGRAPH SHOWING MIS-MATCH IN WELDING



RADIOGRAPH SHOWING CRACKS IN WELDING



RADIOGRAPH SHOWING TUNGSTEN INCLUSION IN WELDING



RADIOGRAPH SHOWING SLAG INCLUSION IN WELDING



RADIOGRAPH SHOWING CLUSTER POROSITY IN WELDING



RADIOGRAPH SHOWING SUCK BACK IN WELDING



RADIOGRAPH SHOWING BURN THROUGH IN WELDING



RADIOGRAPH SHOWING UNDERFILL IN WELDING



RADIOGRAPH SHOWING EXCESS REINFORCEMENT IN WELDING

RADIOGRAPHY ACCEPTANCE STANDARD (ASME SECTION-I, PW-51) Crack, Lack of Fusion & Lack of Penetration are not acceptable. Any other elongated indication on the radiograph

6mm for thickness (t) up to 19mm is acceptable. 1/3 t for thickness (t) 19mm to 57mm is acceptable. 19mm for thickness (t) over 57mm is acceptable.

Total length of aligned indication greater than thk. of weld, in alength of radiograph, which is 12 times in length of thickness ofweld is not acceptable. If, distance between successive indicationexceeds 6L is acceptable. Where, L is the length of longestdiscontinuity in the group.

Rounded indication acceptance standard as per A-250.


RADIOGRAPHY ACCEPTANCE STANDARD (ASME SECTION-I, PW-51)


APPENDIX A-250 / TABLE A 250.3.2

RADIATION SAFETY Use of radiation sources in industrial radiography is heavily

regulated by state and federal organizations due topotential public and personal risks.


RADIATION SAFETY There are many sources of radiation. In general, a person receives

roughly 100 mrem/year from natural sources and roughly 100mrem/year from manmade sources.


RADIATION SAFETY X-rays and gamma rays are forms of ionizing radiation, which means

that they have the ability to form ions in the material that ispenetrated. All living organisms are sensitive to the effects ofionizing radiation (radiation burns, x-ray food pasteurization, etc.)

X-rays and gammarays have enoughenergy to liberateelectrons fromatoms and damagethe molecularstructure of cells.

This can causeradiation burns orcancer.


RADIATION SAFETY Technicians who work with radiation must wear monitoring devices

that keep track of their total absorption, and alert them when theyare in a high radiation area.

Survey Meter Pocket Dosimeter Radiation Alarm Radiation Badge


RADIATION SAFETY There are three means of protection to help reduce exposure to

radiation:


Advance Technology in RT: Real Time Radiography

Real-time radiography (RTR), or real-time radioscopy, is a nondestructiveexamination (NDE) method whereby an image is produced electronicallyrather than on film so that very little lag time occurs between the itembeing exposed to radiation and the resulting image. In most instances,the electronic image that is viewed, results from the radiation passingthrough the object being inspected and interacting with a screen ofmaterial that fluoresces or gives off light when the interaction occurs.


Advance Technology in RT: Weld images from Real Time Radiography


RTR image showing

Voids in welding

RTR image showing

Crack in welding

APPLICATION OF RT Can be applied to all materials. E.g. Ferrous & Non-ferrous, metallic &

non-metallic and all composites. Sensitive for all volumetric type of defects.DEFECTS CAN BE DETECTED BY RT: All type of cracks Lack of fusion (LoF) Lack of Penetration (LoP) Mismatch Inclusions (Tungsten, Slag & Oxides) Excess reinforcement Excess penetration (EP) Underfill Undercut Oxide Suck back Burn through


ADVANTAGES Permanent record & track of each and every welding is possible

through film storage and joint identification. Technique is not limited by material type or density. Can inspect assembled components. Minimum surface preparation required. Sensitive to changes in thickness, corrosion, voids, cracks, and

material density changes. Detects both surface and subsurface defects. Provides a permanent record of the inspection.


LIMITATIONS Many safety precautions for the use of high intensity radiation. Many hours of technician training prior to use. Access to both sides of sample required. Orientation of equipment and flaw can be critical. Determining flaw depth is impossible without additional angled

exposures. Expensive initial equipment cost.


RT IN BOILER: HEADER

Circumferential welds Orifice welds

COIL Tube to tube welding

PANEL Tube to tube welding


INTRODUCTION TOULTRASONIC TESTING

OUTLINE Working principle

Types of sound waves & their propagation

Type waves & particle motion

Wavelength & frequency

Attenuation of sound wave

Acoustic impedance & its important

Reflection & transmission

Refraction

UT equipments

Data Presentation

Calibration block

DAC Curve

UT of welding

Advance technologies in UT

Advantages & Limitations of UT

Code acceptance criteria

ULTRASONIC TESTING (UT)

WORKING PRINCIPLE: In Ultrasonic Testing the High frequency sound waves (Ultrasonic -

Energy) are sent into the object. The sound waves travel throughthe material and the waves are reflected at interfaces.

The probe picks up the reflected wave and an analysis of this signalis done.



SOUND WAVE PROPAGATION:

At atomic level when vibration takes place in particle, It generatessound wave.

Sound wave propagation depends on particle vibration direction.

WAVE TYPES IN

SOLIDS

PARTICLE

VIBRATIONS

LongitudinalParallel to wave

direction

Transverse (Shear)Perpendicular to wave

direction

Surface - Rayleigh Elliptical orbit -

symmetrical mode



WAVELENGTH AND FREQUENCY:

ACOUSTIC IMPEDANCE Sound travels through materials under the influence of sound pressure.

Because molecules or atoms of a solid are bound elastically to oneanother, the excess pressure results in a wave propagating through thesolid.

The acoustic impedance (Z) of a material is defined as the product of itsdensity (p) and acoustic velocity (V). It is resistance of material to passageof the sound beam through material.

Z = pV

Acoustic impedance is important in

the determination of acoustic transmission and reflection at the boundary of two materials having different acoustic impedances. Reflection is directly proportional to impedance ratio of two material.

Air to any solid material impedance ratio is highest. So, UT is always sensitive for planer defects.

assessing absorption of sound in a medium.



REFLECTION AND TRANSMISSION:

REFRACTION

When an ultrasonic wave passes through an interface betweentwo materials at an oblique angle, and the materials havedifferent indices of refraction, both reflected and refractedwaves are produced.


ATTENUATION OF SOUND WAVE:

Ultrasonic attenuation is the decay rate ofthe wave as it propagates through material.

When sound travels through a medium, itsintensity diminishes with distance due toScattering and Absorption.

Scattering is the reflection of the sound indirections other than its original direction ofpropagation.

Absorption is the conversion of the sound energyto other forms of energy.

The combined effect of scattering and absorptionis called attenuation.


BASIC SET UP OF UT:

Transducer (1)

Cable (2)

Ultrasonic Flaw Detector (3)

Couplant (4)

3 2

1

4


TRANSDUCERS (PROBE)

Principle : Converts Electrical Energy into Mechanical Energy andvice-versa(Pie)


PIEZOELECTRIC MATERIAL

Case-1 - Mechanical Energy converts into Electrical energy

Case-2 - Electrical Energy converts into Mechanical Energy


PROBE (TRANSDUCER) TYPES:

Contact Transducers

Used for direct contact inspections.

Coupling materials of water, grease, oils, orcommercial materials are used to remove theair gap between the transducer and thecomponent being inspected.

Immersion Transducers

Do not contact the component.

Specially designed to operate in a liquidenvironment.

Transducers are available with a planer,cylindrically focused or sphericallyfocused lens.


PROBE (TRANSDUCER) TYPES (CONT.):0 (Normal) beam TransducersSingle Crystal Probe:

Single crystal element is used both for transmitting andreceiving.

Dual Crystal Probe:

Contain two independently operated elements in a singlehousing.

One of the elements transmits and the other receives theultrasonic signal.

Applicable for the inspection of course grained material.

Well suited for making measurements in applications wherereflectors are very near the transducer.

Angle beam probe

Used to introduce a refracted shear wave into the test material.

Available in a variety of fixed angles or in adjustable versionswhere the user determines the angles of incidence andrefraction.

Probe angles 45, 60 and 70 are being used widely.


Single Point Dual Point Multi Point

WAVE INTERFERENCE The sound that emanates from an ultrasonic transducer does not originate

from a single point, but instead originates from many points along thesurface of the piezoelectric element

This results in a sound field with many waves interacting or interferingwith each other.

When waves interact, they superimpose on each other, and the amplitudeof the sound pressure or particle displacement at any point of interactionis the sum of the amplitudes of the two individual waves.



NEAR FIELD AND FAR FIELD:

Near Field: Wave interference leads to extensive fluctuations in thesound intensity near the source and is known as the near field.

Far Field: The area just beyond the near field is where the soundwave is well behaved and at its maximum strength. Therefore,optimal detection results will be obtained when flaws occur in thisarea.

DEAD ZONE:

It is the interval following the surface of a test object to the nearestinspectable depth. Any interval following a reflected signal where nodirect echoes from discontinuities cannot be detected, due tocharacteristics of the equipment.


PULSER /RECEIVER OR ULTRASONIC FLAW DETECTOR (UFD):

The pulser section of the instrument generates short, large amplitudeelectric pulses of controlled energy, which are converted into shortultrasonic pulses when applied to an ultrasonic transducer.

In the receiver section the voltage signals produced by the transducer,which represent the received ultrasonic pulses, are amplified. Theamplified radio frequency (RF) signal is available as an output fordisplay or capture for signal processing.


Analog

Digital

COAXIAL CABLEA: outer plastic sheathB: woven copper shieldC: inner dielectric insulatorD: copper-plated core


COUPLANT:Couplant is used to nullify air gap between probe and specimen surface.

Couplant medias areWaterOilGreaseCellulose paste


DATA REPRESENTATION:

A-Scan

B-Scan

C-Scan


A-SCAN The A-scan presentation displays the amount of received ultrasonic

energy as a function of time. The relative amount of received energyis plotted along the vertical axis and the elapsed time (which may berelated to the sound energy travel time within the material) isdisplayed along the horizontal axis.


A-SCAN UT VISUALIZATION (NORMAL PROBE)


ULTRASONIC TESTING (UT)A-SCAN UT VISUALIZATION (ANGLE PROBE)

B-SCAN The B-scan presentations is a profile (cross-sectional) view of the test

specimen. In the B-scan, the time-of-flight (travel time) of the sound energy is displayed along the vertical axis and the linear position of the transducer is displayed along the horizontal axis.

In the B-scan, the depth of the reflector and its approximate linear dimensions in the scan direction can be determined.


C-SCAN The C-scan presentation provides a plan-type

view of the location and size of test specimenfeatures. The plane of the image is parallel tothe scan pattern of the transducer.

C-scan presentations are produced with anautomated data acquisition system, such as acomputer controlled immersion scanningsystem.


CALIBRATION Calibration refers to the act of evaluating and adjusting the precision

and accuracy of measurement equipment.

REFERENCE STANDARDS : To establish a general level of consistency in measurements and to help

interpret and quantify the information contained in the received signal. To validate that the equipment and the setup provide similar results from

one day to the next and that similar results are produced by differentsystems.

Help the inspector to estimate the size of flaws. Signal strength depends on both the size of the flaw and the distance

between the flaw and the transducer. The inspector can use a reference standard with an artificially induced flaw

of known size and at approximately the same distance away for thetransducer to produce a signal

By comparing the signal from the reference standard to that received fromthe actual flaw, the inspector can estimate the flaw size.


Calibration Blocks


DISTANCE AMPLITUDE CORRECTION (DAC):

Acoustic signals from the same reflecting surface will havedifferent amplitudes at different distances from thetransducer.

Acoustic signals from the same reflecting surface will havedifferent amplitudes at different distances from thetransducer.


UFD


UT OF WELDED JOINTS:



SCANNING PATTERN AND DIRECTION:

Maximum reflection can be achieved when flaw is lyingperpendicular to beam direction.

Probe angle selection should be such that beam shall hitperpendicular to the side wall of weld groove.

The best practice is to scan from two different direction andwith two different angle beam probes.

Mainly three types of scanning patterns are used to getreflection from defects lying at any orientation. Longitudinal scanning Transverse scanning Orbital scanning

ADVANCED UT (PHASED ARRAY)

Phased arrays use an array of elements, all individuallywired, pulsed and time-shifted.

These elements can be a linear array, a 2D matrix array,a circular array or some more complex form.


WORKING PRINCIPLE: All arrays are operated individually, It will give us various types of wave

configuration.

Ultrasonic phased arrays use a multiple element probe whereby theoutput pulse from each element is time delayed in such a way so asproduce constructive interference at a specific angle and a specific depth.These time delays can be incremented over a range of angles to sweep thebeam over the desired angular range.

Focused Normal beam Focused Shear wave



DATA PRESENTATION:

TIME OF FLIGHT DEFRACTION: The TOFD technique is based on diffraction of ultrasonic waves on tips of

discontinuities, instead of geometrical reflection on the interface of thediscontinuities

When ultrasound is incident at linear discontinuity such as crack, diffraction takesplace at its extremities. Usually TOFD technique uses a pair of probes.

One Acts as an emitter of ultrasound, the other as a receiver. The longitudinalsound beam can encounter obstacles on its path, which cause reflected anddiffracted signals. When the probes are moved parallel along the weld, theresultant waveforms are digitized, stored on hard disk and displayed on the screen.

Using this advanced technique gas and binding defects, slag inclusions and crackscan be detected independent of defect orientation with very accurate sizing of thedefects (0.5-1.0 mm).


Transmitter Receiver

Lateral wave

Upper tip

Lower tip

Back-wall reflection


TOFD SIGNALS:

The crack blocks the Lateral Wave

And the lower tip appears on the A-scan

21

1

2

ULTRASONIC TESTING (UT)DATA PRESENTATION:

ULTRASONIC TESTING (UT)APPLICATION OF UT: Can be applied to all materials. E.g. Ferrous & Non-ferrous, metallic

& non-metallic and all composites. Practically there is no anythickness limitation to perform UT.

DEFECTS CAN BE DETECTED BY UT: All type of cracks Lack of fusion (LoF) Lack of Penetration (LoP) Inclusions (Tungsten, Slag & Oxides) Excess penetration (EP) Undercut

ADVANTAGES OF UT: It is sensitive to both surface and subsurface discontinuities. The depth of penetration for flaw detection or measurement is

superior to other NDT methods. Only single-sided access is needed when the pulse-echo

technique is used. It is highly accurate in determining reflector position and

estimating size and shape. Minimal part preparation is required. Electronic equipment provides instantaneous results. Detailed images can be produced with automated systems. It has other uses, such as thickness measurement, in addition to

flaw detection.


LIMITATIONS OF UT: Surface must be accessible to transmit ultrasound. Skill and training is more extensive than with some other methods. It normally requires a coupling medium to promote the transfer of

sound energy into the test specimen. Materials that are rough, irregular in shape, very small,

exceptionally thin or not homogeneous are difficult to inspect. Cast iron and other coarse grained materials are difficult to inspect

due to low sound transmission and high signal noise. Linear defects oriented parallel to the sound beam may go

undetected. Reference standards are required for both equipment calibration

and the characterization of flaws.


ULTRASONIC TESTING (UT)ACCEPTANCE CRITERIA AS PER ASME SECTION-1 PW -52: Technique and standards for ultrasonic examination are given in ASME

Section V, Article 4 & 5. Imperfections that cause an indication greater than 20% of the reference

level shall be investigated to the extent that the ultrasonic examinationpersonnel can determine their shape, identity, and location, and evaluatethem in terms of PW-52.3.1 and PW-52.3.2.

Cracks, lack of fusion, or incomplete penetration are not acceptableregardless of length.

Other imperfections are unacceptable if the indication exceeds thereference level and their length exceeds the following: 6 mm for t up to 19 mm 13t for t from 19 mm to 57 mm 19 mm for t over 57 mm

Notes :- where t is the thickness of the weld being examined. If the weldjoins two members having different thicknesses at the weld, t is the thinnerof these two thickness.

UT IN BOILER: Header

T-piece branch connection Manifold support bolts Depth confirmation (If repair found in Cir. Seams) Above 48mm thk


MATERIAL

FLAW TYPE

Surface

flaw

Sub-surface

flaw

Internal

flaw

Lack of

fusion

Inclusions

e.g. slag, T.I.

Material

quality

Lamination &

thickness

measurement

Ferrous forgings M.T.M.T.

U.T.

R.T.

U.T.---

R.T.

U.T.--- U.T.

Ferrous raw

material

M.T. M.T.

U.T.U.T. ---

M.T.

U.T.--- U.T.

Ferrous tube &

pipe

M.T.

E.T.

M.T.

U.T.U.T. U.T.

M.T.

U.T.--- U.T.

Ferrous weldsM.T.

U.T.U.T.

R.T.

U.T.

R.T.

U.T.

R.T.

U.T.--- U.T.

Steel castings M.T.M.T.

U.T.

R.T.

U.T.---

R.T.

U.T.--- U.T.

Iron castings M.T.U.T.

E.T.U.T. ---

R.T.

U.T.U.T. U.T.

Non-Fe materialsP.T.

E.T.---

R.T.

U.T.U.T.

P.T.

U.T.--- U.T.

Fe finished

materialsM.T.

U.T.

E.T.

R.T.

U.T.U.T.

M.T.

U.T.--- U.T.

Non-Fe finished

materials

P.T.

E.T.

U.T.

E.T.

R.T.

U.T.---

U.T.

E.T.--- U.T.

APPLICATION OF N.D.E.

APPLICATION OF N.D.E.N.D.E. IN BOILER INDUSTRY: Boiler testing for welding defects both during manufacturing and in

service. Boiler piping thickness measurement and turbine component testing.

THANK YOU

An Introduction of NDE -- NDT

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