☺Sub.~ Material science & metallurgy 1

Nondestructive Test ~Visual Inspection, LPT, MPT

Application, Advantage, Disadvantage

☺Guided by☺Mohit Lakhvani☺Yogesh Choudhary

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NAME ROLL NO. ENROLLMENT NO.• Taral Soliya 45 130030119109

Batch ~ FY☺Prepared By

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The use of noninvasive techniques to determine the integrity of a material, component or structure

or quantitatively measuresome characteristic ofan object.

i.e. Inspect or measure without doing harm.

Definition of NDT

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Most Common NDT Methods Visual Liquid Penetrate Magnetic Particle Ultrasonic Eddy Current X-ray

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Most basic and common inspection method.

Tools include fiberscope's, bore scopes, magnifying glasses and mirrors.

Visual Inspection

Robotic crawlers permit observation in hazardous or tight areas, such as air ducts, reactors, pipelines.

Portable video inspection unit with zoom allows

inspection of large tanks and vessels, railroad tank

cars, sewer lines.

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Liquid Penetration Test ~ LPT Liquid penetrant inspection is a

method that is used to reveal surface breaking flaws by bleed out of a colored or fluorescent dye from the flaw.

The technique is based on the ability of a liquid to be drawn into a "clean" surface breaking flaw by capillary action.

After a period of time called the "dwell," excess surface penetrant is removed and a developer applied.It draws the penetrant from the flaw to reveal its presence.

Colored (contrast) penetrants require good white light while fluorescent penetrants need to be used in darkened conditions with an ultraviolet "black light".

Liquid Penetration Test ~ LPTA liquid with high surface wetting

characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects.

A developer (powder) is applied to pull the trapped penetrate out the defect and spread it on the surface where it can be seen

Visual inspection is the final step in the process. The penetrate used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.8

Basic ProcedurePre-CleanPenetrant Application Excess Penetrant RemovalDeveloper ApplicationInspect/EvaluatePost-clean

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Liquid penetrant inspection (LPI) is one of the most widely used nondestructive evaluation (NDE) methods. Its popularity can be attributed to two main factors: its relative ease of use and its flexibility.LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous. Materials that are commonly inspected using LPI include the following: Metals (aluminum, copper, steel, titanium, etc.) Glass Many ceramic materials Rubber Plastics

Common Uses of Liquid Penetrant Inspection

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AdvantagesThe method has high sensitivity to small surface discontinuities. The method has few material limitations, i.e. metallic and nonmetallic, magnetic and nonmagnetic, and conductive and nonconductive materials may be inspected. Large areas and large volumes of parts/materials can be inspected rapidly and at low cost. Parts with complex geometric shapes 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 inexpensive. 11

DisadvantagesOnly surface breaking defects can be detected. Only materials with a relatively nonporous surface can be inspected. Precleaning is critical since contaminants can mask defects. Metal smearing from machining, grinding, and grit or vapor blasting must be removed prior to LPI. 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.12

Penetrant TypeFluorescent Visible

MethodWater WashablePostemulsifiable – LipophilicSolvent RemovablePostemulsifiable – Hydrophilic

Developer FormDry PowderWet, Water SolubleWet, Water SuspendableWet, Non-Aqueous

Choices of Penetrant Materials

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Magnetic Particle Test The part is magnetized. Finely milled iron particles

coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions.

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Basic ProcedureComponent pre-cleaning Introduction of magnetic field Application of magnetic media Interpretation of magnetic particle indications

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Permanent magnets and electromagnetic yokes are also often used to produce a longitudinal magnetic field. The magnetic lines of force run from one pole to the other, and the poles are positioned such that any flaws present run normal to these lines of force.

Producing a Longitudinal Field Using Permanent or Electromagnetic Magnets

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Dry Magnetic ParticlesMagnetic particles come in a variety of colors. A color that produces a high level of contrast against the background should be used.

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Wet Magnetic ParticlesWet particles are typically supplied as visible or fluorescent. Visible particles are viewed under normal white light and fluorescent particles are viewed under black light.

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AdvantagesCan detect both surface and near sub-surface defects. Can inspect parts with irregular shapes easily. Precleaning of components is not as critical as it is for some other inspection methods. Most contaminants within a flaw will not hinder flaw detectability. Fast method of inspection and indications are visible directly on the specimen surface. Considered low cost compared to many other NDT methods. Is a very portable inspection method especially when used with battery powered equipment.

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DisadvantagesCannot inspect non-ferrous materials such as aluminum, magnesium or most stainless steels. Inspection of large parts may require use of equipment with special power requirements. Some parts may require removal of coating or plating to achieve desired inspection sensitivity. Limited subsurface discontinuity detection capabilities. Maximum depth sensitivity is approximately 0.6” (under ideal conditions). Post cleaning, and post demagnetization is often necessary. Alignment between magnetic flux and defect is important

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Flaw Detection and Evaluation Leak Detection Location Determination Dimensional Measurements Structure and Microstructure Characterization Estimation of Mechanical and Physical Properties Stress (Strain) and Dynamic Response Measurements Material Sorting and Chemical Composition

Determination Assist in product development Screen or sort incoming materials Monitor, improve or control manufacturing processes Verify proper processing such as heat treating Verify proper assembly Inspect for in-service damage

Some Uses of NDT Methods

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Reference How stuff works Wikihow Non destructive testing (Book by N.J.Shah)

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THANK YOU

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