Inspection

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Types of deffects

Inherent defects – present during intial production of raw materials .

Processing defects – resulted from the manfacturing process

Service defects – occurred during the operation

Examples that may cause deffects

Blowholes – gas trapped during solidification process .

Hardening cracks – rapid volume change .

Tempering cracks – rapid heating .

Types of inspection

Inspection have many types wich are :

Visual inspection Mechanical measurements Destructive testing Non destructive testing Hammer test Hydrostatic test

Non Destructive Test ( NDT )

The use of noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object .

Inspect or measure without doing harm .

Uses of NDT

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

Methods of NDT

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

Visual Inspection .

Most basic and common inspection method

Portable video inspection unit with zoom allows inspection of large tanks and vessels

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

Liquid penetrant inspection Cleaner

Penetrant liquid

Developer

Usually used to show cracks or porosity .

Procedures of liquid penetrant test

Advantages and disadvantages

Advantages : applicable for complex shapes no need of equipments Used for metals & non metals

Diadvantages : Detection of surface defects only Difficult to detect on rough surfaces

Magnetic particle test

Circular or longitudinal magnetization

The part is magnetized Iron particles coated with a dye

pigment are then applied to the specimen.

Leakage will be found forming the shape of the deffect

Advantages & disadvantages

Advantages : The best for defects near surface Low cost Portable Give efficent results

Disadvantages : Materials that only can be

magnetised Removing magnetisation is a must

Ultrasonic inspection

High frequency sound waves are introduced into a material

They are reflected back from surfaces or flaws.

Reflected sound energy is displayed versus time

From the graph we can detect the defect

0 2 4 6 8 10

initial pulse

crack echo

back surface echo

plate

crack

Advantages of ultrasonic test

Not harmful

Easy to store results

Use only one surface

Portable

Can detect inner and deep defects

The most efficient NDT

Radiography test

Radiation used in tests

higher energy (shorter wavelength) than electromagnetic waves

The radiation can come from an X-ray generator or a radioactive source.

High Electrical Potential

Electrons -+

Exposure Recording Device

Radiation Penetrate the Sample

The part is placed between the radiation source and a piece of film.

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

X-ray film

= more exposure

= less exposure

Eddy current test

Eddy current testing is particularly well suited for detecting surface cracks

can also be used to make electrical conductivity and coating thickness measurements.

Conductive material

CoilCoil's

magnetic field

Eddy currents

Eddy current's magnetic field

Applications of NDT

Inspection of Raw Products

Inspection Following Secondary Processing :

Machining , Welding , Grinding ,Heat treating

In-Services Damage Inspection :

Cracking , Corrosion ,Wear , Heat Damage

Pressure vessel inspection The failure of a pressure vessel can result in the

rapid release of a large amount of energy. inspection by radiography and ultrasonic testing.

Pipeline inspection

NDT is used to inspect pipelines to prevent leaks that could damage the environment

Visual inspection radiography electromagnetic testing

Remote visual inspection

Radiography of weld joints.

Storage tank inspection

Robotic crawlers use ultrasound to inspect the walls of large above ground tanks for signs of thinning due to corrosion.

Cameras on long articulating arms are used to inspect underground storage tanks for damage.

Thank you

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