VISUAL TESTING, LIQUID PENETRANT TESTING

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A PRESENTATION ON NEST NDT
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• Nest (National Employment Service and Training)

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ABOUT US

• Nest (National Employment Service and
  Training) is a leading training institute for
  ASNT level II. We are the only training centre
  giving 100 placement assistance to the
  candidates till candidates get placed. Our
  trainers are having more than ten years of field
  experience in industries like petroleum
  refineries and power plant (nuclear thermal).
  The candidates will get both theoretical and
  practical during the training session. We are
  moulding our candidates with advance training
  medium like visual and audio to enrich their
  knowledge. Our candidates will get a globally
  authentication certificates from ASNT America
  Society for Non Destructive Testing level II as
  per SNT-TC-1A standard on successful completion
  of training and practical exams.
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• Our candidates will get onsite training in the
  particular industries like refineries and power
  plant to get a real time experience. Nest takes
  whole responsibilities of our candidates
  developing in their career. Other than NDT
  training we are providing Motivation class
  personality development session to get through in
  their interviews with fear.

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• Vision
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• Nest Institute of NDT posses high quality
  international standard training for NDT in
  accordance with quality management system and
  pursuing placement for candidates to improve
  their career.
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• Our Mission
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• To give quality training and education along
  with placement for the youngsters to enrich their
  career (or) to make their life delightful.

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Visual Testing

• The earliest and most useful method of NDT is
  visual examination. Important details can be
  collected during VT which would be useful for
  future analysis and also to decide on the types
  of NDT to be used for as further analysis. Also
  VT should be carried out as a complementary
  method to all other NDT methods. VT should
  proceed and succeed all other examinations.
  Inaccessible areas can be inspected by means of
  boroscope and fiber-optic techniques. Depending
  upon the severity of the surface defect and the
  component in use decision will be taken for
  salvaging the component or not. If the product is
  found unacceptable during visual examination
  itself further NDT need not be carried out thus
  saving time and cost of inspection

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VT is selected for detecting the following
discontinuities

• Surface deposits
• Scaling
• Corrosion
• Discoloration
• Oxidation bulging
• Missing parts
• Mechanical damage
• Dimensional conformance
• Gross effects visible on the surface
• Distortion of components during fabrication and
  in services
• General corrosion on the surface of a component

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Liquid Penetrant Testing

• Liquid penetrant testing (LPT) is another
  means of enhancing the capability of visual
  examination. It is suitable for use on smooth
  surfaces of all materials magnetic as well as
  non-magnetic. It is limited to surface defects.
  Its inability to indicate the depth or breadth of
  flaw should be kept in mind while selecting this
  method for particular application.
• Use of LPT for porous materials is ruled out
  since the absorption into the pores would mask
  the presence of defects. A clean surface is a
  pre-resist as penetrant cannot enter in to the
  cracks that are filled with dirt oil or other
  matter.
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• Size shape weight and number of workpieces to
  be inspected often influence the selection of a
  penetrant system. The desired degree of
  sensitivity and the cost are the most important
  factors in selecting a system.
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• LPT can also be used for leak testing. In this
  case the component casting is filled with
  penetrant and developer is applied outside the
  surface.

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• LPT is selected for detecting the following types
  of discontinuities on the surface of a component.
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• Cracks of any orientation
• Porosity
• Pin holes
• Voids
• Forging laps
• Forging bursts
• Lamination in plates
• Various types of weld defects
• Corrosion cracks
• Creep fissures
• Fatigue cracks

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Magnetic Particle Testing

• While LPT is effective only for fine surface
  discontinuities the need remains to detect
  larger surface flaws or those present just below
  the surface. The need is met by magnetic particle
  testing (MPT). This technique is applicable only
  for ferromagnetic materials. MPT is a considered
  more sensitive than LPT. MPT requires a higher
  degree or operator expertise to ensure that the
  magnetic fields are aligned in the correct
  direction in order to detect the defect. Flaws
  oriented perpendicular to the induced magnetic
  field is only reliably detectable. Hence the
  challenge is to induce magnetic field lines in a
  given work piece so that they are most likely to
  be perpendicular to the flaw orientation.
  Therefore prior knowledge on flaw orientation
  and or introduction of magnetic fields in several
  directions are is essential.
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• It is commonly agreed that defects breaking the
  surface are most severe amongst the various
  discontinuities occurring in components. For
  dynamically loaded structures their removal is
  essential. Their detection in ferrite materials
  is most easily accomplished by MPT. Since the
  depth determination of the surface breaking
  cracks is almost impossible crack depth
  measurements may be additionally employed to
  asses them. Detection of subsurface defects by
  MPT is impossible if the components are thin but
  generally it requires ideal testing conditions.

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• MPT is used for detecting following
  discontinuities in ferromagnetic materials.
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• Surface discontinuities
• Cracks and tears
• Porosity
• Shrinking cavities
• Slag inclusions
• Voids
• Forging laps
• Grinding cracks
• Corrosion cracks
• Fatigue cracks
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• Discontinuities just below the surface (within
  around 6mm depth from the surface sensitivity
  goes down as a defect is deeper)
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• Larger size cracks in various orientations
• Pores
• Slag inclusions
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Radiography Testing

• The other NDT methods are used for detection of
  defects which are open to the surface nearer to
  the surface. To detect more deeply seated
  discontinuities NDT methods with test medium
  capable of deeper penetration and system that
  senses even minute changes in the
  characteristics behaviour of the test medium is
  required. Radiographic inspection is one of the
  most widely used methods of NDT as this is
  applied to all metals and alloys both ferrous
  and nonferrous for detection of volumetric type
  of defects. The range of capabilities offered by
  the variety of sources and equipments has brought
  radiography to the forefront of NDT techniques.
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• Testing of multilayer vessels and welds is
  generally a difficult task due to in accessible
  inner layers. RT is the only NDT method to
  evaluate multilayered vessels during
  manufacturing stages and inservice.

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• Development of micro focal X-ray units has made
  it possible to extend radiographic practice to
  meet the requirements of more stringent quality
  levels demanded for critical applications
  besides a host of new applications. It is know
  that the sensitivity in radiography depends to a
  large extend on the focal spot size. In micro
  focal radiography the focal spot size is less
  than 100microns and typically 15-50 micron as
  compared to a few mm or ½ a mm in conventional
  radiography. Using microfocal RT intricate
  geometrical components such as tube to tube
  sheet. Welds can be tested with a sensitivity of
  even 1 of wall thickness 0-3mm. microfocal RT
  can be used for detection of micro cracks of
  around 25micron in size. Another application of
  microfocal RT is to check the integrity of
  micro-welds used electronic integrated circuits.
• One of the advantages of RT is that no prior
  preparation of the surface of the component is
  necessary. The main disadvantage of the RT is the
  possible hazards due to exposure to radiation if
  proper care is not taken.

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• RT is selected to detect and size the following
  types of discontinuities
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• Cracks (parallel to the radiation beam)
• Volumetric defects such as slag inclusions voids
  etc
• Porosity
• Blockages or deposits inside the pipe lines are
  pressure vessels
• Material thickness
• To detect hidden foreign material inside a
  component
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Ultrasonic Testing

• Ultrasonic testing involves use of high
  frequency sound waves coupled to the components
  to be inspected and studying the reflection
  pattern of these waves. UT is finding increased
  applications in various industries. Several wave
  modes such as longitudinal shear and surface
  waves can be used depending on the orientation
  and location of the discontinuities. Different
  techniques such as pulse-echo through
  transmission and pitch-catch or employed. The
  advantages of UT are real time availability of
  results higher penetrating power of these waves
  higher sensitivity for planner defects
  independence sensitivity over depths low cost
  for inspection higher portability to the
  equipment and compatibility for automation. But
  the subjectivity of the results on the operators
  training and skill is stumbling block for its
  wider acceptance. With the advent of
  microprocessors and automation operator
  dependability is being eliminated to a larger
  extent and UT finding increased applications in
  industries such as power railways chemical
  aerospace etc

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• UT of cast metals and alloys is renderd
  difficult due to the influence of casting
  intricacy micro structural variations and
  surface roughness. Defects occurring in the cast
  structure have irregular surfaces which scatter
  the aquostic waves and makes UT more difficult.
  Hence successful use of UT for inspection of
  castings depends greatly upon the skill and
  expertise of the operator.
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• UT is the most suitable method of NDT for
  inservice inspection (ISI) of components in power
  plants chemical process industries etc. Many
  times RT cannot be applied for ISI due to the
  requirements of two side accessibility. UT is
  more sensitive flaw growth monitoring has
  compared with RT in view of all these advantages
  the first choice of ISI is UT for volumetric
  defects in components except for heat exchangers
  and condensers where ECT is preferred.

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• UT Is Selected To Detect The Size The Following
  Type Of Discontinuities
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• Surface breaking and hidden cracks in any
  orientation
• Inter granular cracks
• Laps
• Laminations
• Volumetric defects such slag inclusions voids
  ect
• Porosity
• Wall thickness measurements
• Creep
• Hydrogen encriptment
• Liquid level measurement
• To detect blockages deposits etc. in the pipe
  lines and pressure vessels
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• THANK YOU
• FOR MORE INFORMATION
• Visit
• nestndt.com