WELDING INSPECTION AND QUALITY CONTROL

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WELDING INSPECTION AND QUALITY CONTROL

• Upon completion of this module you will be able
  to
• Identify the different inspection methods used in
  non destructive testing.
• The uses and the limitations of the different
  inspection methods.
• Perform Visual Inspection.

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• Introduction.
• Inspection, Testing and qualification are
  growing part of QUALITY CONTROL in manufacturing
  and maintenance. Quality Control has become very
  important because of competition and liability.
  To compete in what has become a global
  marketplace, companies must produce the best
  products possible. The cost of inspection and
  testing of products can save greater expenses
  later on when the consumer becomes involved.
  Money that does not have to be spent defending
  the company can be used for research and
  development of new products. The WELDER is the
  person who begins quality control by being
  satisfied only with Quality Welding.

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• The welder starts the inspection in the process
  of welding, making immediate adjustment in
  response to what is being observed in the weld
  pool. This may require changing the amperage, the
  travel speed, the arc length or any of the
  factors that affects quality of the weld bead.
  Finally, the welder gives the completed weld a
  final Visual Inspection to look for any defects
  that could not be seen while welding.

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Common methods used in NDE

• Visual Inspection (VT)
• Magnetic Particle Inspection (MT)
• Liquid (Dye) Penetrant Inspection (PT)
• X-Ray inspection (RT)
• Ultrasonic testing (UT)
• Air or water pressure testing (LT)

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VISUAL INSPECTION VISUAL TEST (VT)

• What is Visual Inspection?
• NDT process non destructive testing is the
  original term used to identify a method of
  inspection that does not destroy a product
  usefulness. Current terms include nondestructive
  inspection (NDI) or nondestructive evaluation or
  examination (NDE)
• Examination with the eye therefore you are only
  able to DETECT SURFACE DISCONTINUITIES.
• Most important and most extensively used
  NDE/NDI/NDT method (before any NDT or DT be
  applied.)
• II. Advantages
• A. Usually inexpensive - the majority of expense
  will be in the inspectors wage.
• B. Equipment is small and inexpensive theres a
  lot of equipment to aid in visual inspection, but
  all small and inexpensive.

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• C. No powered required this makes VT the most
  portable NDT process.
• D. Can avoid defects and costly repairs by able
  to make intermittent inspection
• II. DISADVANTAGES
• Requires training and experience the inspector
  should be familiar with all the welding process.
• Must have a good eyes the AWS requires 20-40
  natural or corrected distance acuity for a
  certified welding inspector.
• May not detect internal defects limited to
  surface discontinuities only, but it might give
  indication of substance indication. Then can be
  supplemented by some other NDT method.
• No permanent records the inspector must
  maintain a written log, supplemented by pictures,
  and tape recorded report.
• Subject to human error must spend adequate time
  to prevent errors.

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• IV. Five steps of Visual Inspection.
• Inspection practice establish a definite
  procedure to insure adequate and consistent
  coverage.
• Inspection prior to welding
• Inspection during welding
• Inspection after welding
• Marking and making repairs
• V. Equipment required.
• Flashlight used to remove shadows when an
  extension lamp cant be used.
• Magnifying glass low power can be used with
  caution, if allowed by customer or code.
• Protective lenses pocket viewer with proper
  shade lens to watch the welding taking place.
• Weld gage are hand held measuring devices used
  to assist during welding and for final
  inspection.

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• E. Hammer and chisel to remove spatter or slag
  from weld prior to inspection.
• F. Temperature Indicating Devices some method
  must be used to determine the preheating,
  interpass and postheating temperatures. Pyrometer
  and tempelstick or crayons are commonly used.
• G. Magnet a magnet can be used to help
  determine a material type.

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Visual Inspection (VT)

• Fillet gauges measure
• The Legsof the weld
• Convexity
• (weld rounded outward)
• Concavity
• (weld rounded inward)
• Flatness

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Measuring Steel Rule
Magnifying Glass
Fillet Weld Gauge
Palm Weld Gauge
Micro Caliper
Vernier Caliper
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• VI. Inspection Before Welding
• Drawing drawing are complete and accurate?
• Position of welds does the position called for
  correspond to the procedure or specification? In
  vertical is direction of travel correct?
• Welding symbols if they are used are they
  complete and accurate?
• Welding procedure is the procedure complete and
  accurate according to the code or specification?

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• E. Material
• Did purchasing obtain the correct material such
  as base metal type and size. The correct
  electrode type size and the correct shielding gas
  type and grade.
• Materials should be checked for defects. Base
  metal should be checked rust, mill, scale,
  laminations or delaminations.
• Is the material preparation correct and according
  to procedure, such as angles and condition after
  preparation.
• F. Assembly
• Inspect for proper fit up, as this will prevent
  discontinuities from occuring.
• Jigs and fixtures will assure proper alignment.
  Make sure they are clean and free spatter and not
  damaged.
• The tack welds are only short welds, but the
  quality must be the same as all other welds. The
  tack welds must be made with the same electrodes
  that are used for the rest of the welds.

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• 4. Pre heat will be used to slow the cooling rate
  and prevent distortion. The pre heat could be
  used prior to tacking and / or prior to welding.
• G. Equipment
• Inspect the equipment for any damaged such as
  damaged cables, damaged ground clamps, or
  electrode holders. Inspect the arc voltage and
  amperage meters making sure they are with in
  range.

• Welder Inspect before welding
• - Root Face
• - Root Gap
• - Bevel Angle
• - Joint and Fit up

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• VII. Inspection DURING welding.
• Electrodes inspect for usage of proper
  electrodes, types, size and storage. Low hydrogen
  type must be stored in a stabilizing oven.
• Root pass the first layer or root pass is the
  most important and is particularly susceptible to
  cracking. Thicker material will crack and will
  require more pre heat.
• Subsequent passes inspection of successive
  layers is sometimes carried out with the
  assistance of workmanship standard. Check for
  contour or undercut as these are good places for
  slag to be trapped. Check for proper cleaning
  between passes as this can prevent slag
  entrapment.

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• D. Crater formation make sure crater are filled
  as this are areas where crack are easily formed.
• E. Weld size and sequence are the weld size
  according to the print and is the layer and
  sequence according to the procedure? The use of
  various gages will determine this.
• VIII. Inspection After welding
• The applicable code or standard it will list
  acceptance standards They will generally cover
  the following areas
• Weld size use gages to check conformance to
  prints
• Contour and finish is the contour convex or
  concave, and what was called for in print? Is
  finish smooth and free from surface
  irregularities.
• Cracks the code or standard will state if any
  is acceptable and what size.

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• 4. Overlap it is an indication of lack of
  fusion
• 5. Undercut if allowed how much?
• 6. Spatter what is excessive?
• IX. Making repairs
• A. When marking areas to be repaired the marking
  should be positive and clear. It should be a
  method that is understood by all involved, should
  be permanent enough to be evident after the
  repair has been made and inspected, and the
  marking must not damaged the part.

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Non Destructive Testing Dye Penetrant Test

• OBJECTIVE
• Upon completion of this module you will be able
  to
• 1. Understand that both Inspection and Testing
  are necessary for Quality Welding.
• 2. Identify the different inspection methods used
  in Non Destructive Testing and Destructive
  Testing
• 3. Describe the uses, the process and the
  limitations of the different non destructive
  inspection methods.
• 4. Perform Dye Penetrant Testing.

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• TESTING
• Testing becomes necessary for several reasons.
  If new welding procedures are employed, the
  manufacturer might be interested in finding out
  if the welding process is producing quality
  welds. For example, a product welded by Shielded
  Metal Arc Welding may be produced more
  cost-effectively by a Gas Metal Arc Welding
  process, but will the quality be the same? The
  manufacturer may be interested in finding out if
  both the gas metal arc welding process and the
  filler metals are compatible with the steel used
  as the base metal. If the steel does not match up
  with the filler metal, no welding will make any
  difference.

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There might also be the question of whether the
welders have enough skill at some other welding
process to make welds as sound as those made by
shielded metal arc welding. No manufacturer wants
to risk the companys reputation with welds that
fails to hold up. The least serious outcome might
be a product that fails the worst could be
injury or death. Testing companies provide an
invaluable service when it is necessary to have
welding examination outside the manufacturers
plant. Testing companies keep records and furnish
the results of weld testing to insurance
companies, government agencies and other
interested parties. Testing companies provide an
important service because, by uncovering problems
in welding, they help manufacturers produce safe
and durable goods and structures that consumers
can live with.
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• TWO METHODS OF TESTING
• 1. NON DESTRUCTIVE TESTING - leaves the weldment
  intact, at least until the results uncover major
  defects in the welding. Consequently,
  nondestructive testing is often preferred when
  testing is necessary.
• 2. DESTRUCTIVE TESTING - results in the
  destruction of weldment. This is a costly
  undertaking because of the time and money
  involved, not to mention the destruction of a
  weldment that might have to be re-welded.
• 1. NON-DESTRUCTIVE TESTING METHODS
• There are FOUR common methods of Non Destructive
  Testing
• Magnetic Particle test
• Dye penetrant test
• Ultrasonic test
• Radiographic test

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• Dye Penetrant Test (DPT) and Fluorescent
  Penetrant Test (FPT) can locate only cracks and
  porosity that have formed on the surface of the
  weld. With the dye penetrant test a highly
  penetrative liquid is applied to a weld that has
  been thoroughly cleaned. Upon drying, a developer
  is applied to the weld. Under normal lighting,
  any defects are outlined, usually in red, where
  the dye has been absorbed.
• With the fluorescent penetrant test, the weldment
  is submerged in a fluorescent dye. It is removed
  from the dye and placed under a black light,
  where any defects in the weld appear greenish
  yellow.
• Defects Detected
• Defects open to surface only Cracks, slag
  inclusion, porosity and undercuts.

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Liquid (Dye) Penetrant Inspection (PT)

• Liquid penetrant inspection uses colored or
  fluorescent dye to check for surface flaws.
• PT will not show sub-surface flaws.
• PT can be used on both metallic and non metallic
  surfaces such as ceramic, glass, plastic, and
  metal.
• PT dose not require the part to be Magnetized.

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• Advantages
• a. Detects very small, tight surface and
  subsurface imperfections
• b. Simple application and easy to interpret
• c. Inexpensive
• d. Use in magnetic and non magnetic materials
  such as ceramic, plastic
• Disadvantages
• a. Time consuming on various steps of the process
• b. Normally no permanent record
• EQUIPMENTS FOR PENETRANT TEST
• Solvent Cleaner
• Penetrant
• Developer

• Process Principle 6 steps
• Surface preparation
• Penetrant application
• Excess penetrant removal
• Developer application
• Inspection / evaluation
• Post cleaning

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DYE PENETRANTS

• Types
• Red
• Flouresant
• CAUTION
• Oil based
• Water washable

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DYE PENETRANTS

• Process Principle 6 steps
• 1. Surface preparation remove oil, grease,
  spatter
• 1.1. Apply Solvent Cleaner to the area to be
  inspected
• 1.2. Use clean rags to remove excess cleaner
  solvent
• 2. Apply Penetrant and wait for 15-20 minutes
  dwelling time
• 3. Remove excess penetrant using clean rags
• 4. Apply Developer and wait 5 - 10 minutes
  dwelling time
• 5. Inspect and evaluate the red color formation
• 6. Post cleaning

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DETECTION
Red Dots will appear if Defect is present. Very
Red Color the defect is deep and not very red the
defect is shallow.
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• II. Application
• Ferrous and non ferrous materials
• Plastic and glass ceramics-insulators-anything
  that is nonporous
• III. Advantages
• Low cost
• Ease in application and interpretation easy to
  apply and interpret result, discontinuities
  readily visible and portable.
• Less training time for applicator easy process
  to learn.
• IV. Limitations
• Detects discontinuities that is open to surface
  only
• Can not be used on porous or absorbent materials
• V. Safety
• a. Ventilation check for toxic fumes from
  testing materials. Check for volatility
  -explosive or fire flash points
• b. Fire safety the test material maybe non
  flammable but the propellant used with spray cans
  maybe extremely flammable.

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• b. Fire safety the test material maybe non
  flammable but the propellant used with spray cans
  maybe extremely flammable.
• VI. Types
• Fluorescent (type A) a dye that emits visible
  light rays when viewed under black light.
• 1. considered to be more sensitive than the
  visible type
• 2. must be viewed under ultraviolet (black
  light) in darkened overall lighting conditions.
  More expensive because of equipment required.
  Limited field use.
• B. Visible (type B) a brilliantly colored dye
  that is highly visible under normal lighting
  conditions
• 1. Use normal lighting for inspection
• 2. considered to be less expensive.
• 3. Simplest to use.
• 4. Easy to use for field work
• 5. no electric power required

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• Dual sensitivity works both fluorescent and
  visible.
• VII. Application
• Follow Approved Procedure
• Clean and dry the surface.
• - Solvent cleaner
• 2. Apply penetrant (brush, spray or dip)
  penetrant power comes capillary action
• 3. Penetration time -minimum dwell time is 5-20
  minutes
• 3. Remove excess penetrant.
• - when using solvent type, put solvent on a
  cloth not on the part
• - excess penetrant will give false indications
• 4. Apply developer an allow developer dwell time
  per standard or specification. A rule of thumb
  developer dwell time is equal to one half
  penetrant dwell time.
• - developer will tend to make discontinuities
  appear larger.

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• 6. Inspect and examine true indications are
  caused by penetrant bleeding from actual
  discontinuities.
• 7. Clean if required same as step 1.
• VII. Liquid Penetrant Comparator
• Ideal temperature range of the material to be
  tested is 60 F 125F. If the test must be done
  outside of this range, further qualification
  maybe required.
• Test block to establish acceptability limits of
  contamination and dilution to see if developer
  and penetrant are OK.
• 1. Plated panels brass panels are plated with
  nickel and chromium are bent to produce cracks.
• 2. steel test blocks annealed type 201 0r 302
  stainless steel. Sandblasted on one side only
  with 100 mesh average size grit, gun held at 18
  at 60 psi to achieve velvety finish.

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• 3. aluminum test blocks type 2024 by heating to
  975F and quenched to form cracks. Used to check
  comparison for operating out of the normal
  temperature range. Used also to qualify penetrant
  if shelf is questionable.
• Preparation for reuse blocks should be cleaned
  with solvent to remove all penetrant from cracks
  and then heated to dry and also to drive out any
  remaining solvent.

end
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OBJECTIVE Upon completion of the module, you
will be able to 1. Describe Magnetic Particle
Testing and its limitations.2. Perform Magnetic
Test

• Magnetic Particle Test (MT) (commonly referred
  to as Magnaflux testing)The magnetic particle
  test begins when Direct Current (DC) electric
  charges is passed between two poles. The forces
  line up until there is a break in these magnetic
  lines of force.
• Magnetic particles are applied to the weld in the
  form of powder. Nothing unusual results when the
  welding is sound, but when the welding might be
  defective, a break is created in the lines of
  force. The magnetic particles become attracted to
  the defect, which develops north and south poles
  at the edge of the defect, outlining the defect.

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• Equipment
• 1. Iron Particle, wet or dry or flourescent
• 2. Special power source
• 3. Ultraviolet light for the flourescent type
• DEFECTS DETECTED
• 1. Surface and near surface discontinuities
• 2. Cracks
• 3. Porosity
• 4. Slag Inclusions
• 5. Incomplete Fusion
• Advantages
• 1. Detects discontinuities not visible to the
  naked eyes
• 2. Useful in checking edges prior to welding and
  repairs
• 3. No size restrictions
• Disadvantages
• 1. Used in magnetic materials only
• 2. Surface roughness may distort magnetic field
• 3. Normally no permanent record

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Magnetic Particle Inspection (MT)

• Magnetic Particle Inspection (commonly referred
  to as Magnaflux testing) is only effective at
  checking for flaws located at or near the
  surface.
• MT uses a metallic power or liquid along with
  strong magnetic field probes to locate flaws.
  (Particles will align along voids)
• MT can only be used on materials that can be
  magnetized. It can not be used be used for
  nonmagnetic materials such as Austenitic
  Stainless steel and aluminum.
• Principle
• An electric current is allowed to flow in or an
  electromagnet is applied to part of the specimen
  to cause magnetic flux to flow in the specimen.

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• If a defect exist in the surface layer, it blocks
  the flux flow, so the flux flow is directed
  around the defect while it partially leaks to the
  air. The leaking flux forms a pair of magnetic
  poles, S and N, on both sides of the defect.(as
  shown)

SN
SN
SN
SN
SN
SN
SN
SN
SN
SN
SN
SN
N
S
Fig. A
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• Since the magnetic poles have larger attractive
  force than the surrounding material surface,
  magnetic particles are attracted by and adhere to
  the magnetic poles while attracting each other.
  As a result, a magnetic particle pattern wider
  than the defect is formed on the surface around
  the defect.

Width of magnetic particle pattern
Width of defect
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• To enable the formation of a proper magnetic
  particle pattern for defect indication, the
  orientation of the defect and magnetic field must
  be taken into account.
• Two methods of magnetizing the weld zone.
• The YOKE method which uses an electromagnet
• The PRODE method in which electrode are applied
  to the specimen to allow current to flow in the
  specimen.
• - not applicable to high tensile steel since it
  can form a short circuit between specimen and
  electrodes causing a defect resembling an arc
  strikes.
• - effective to detecting defects not exposed but
  existing near the surface.

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Two methods of magnetizing the weld zone.
2. The PRODE method in which electrode are
applied to the specimen to allow current to flow
in the specimen.

1. The YOKE method which uses an electromagnet

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MAGNETIC PARTICLE

• Two types of magnetic particles
• Fluorescent type
• Non fluorescent type

• Methods of particle application
• Wet method magnetic particles are dispersed by
  suspension in water or kerosene and the
  suspension is applied to the specimen surface.
• Dry method magnetic particle are dispersed in
  the surface of the specimen.

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• CoatingsUnfortunately, ASTM E-1444 specifies
  that Magnetic Particle testing shall not be
  performed with nonmagnetic coatings (paint, etc.)
  in place that exceed 0.003" (0.08mm) in
  thickness, or ferromagnetic coatings
  (electroplated nickel, etc.) that exceed 0.001"
  (0.03mm) in thickness.That is not very thick! So
  be careful on those painted surfaces.......don't
  forget the chance of poor bonding on those thin
  coatings.Current TypesASTM E-1444 recommends
  Half-wave rectified AC is best for the dry
  particle method.For defects open to the surface
  use AC only.When using Wet particle method for
  subsurface defects, use full-wave rectified AC.

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• YokesFunny, but look at the difference,
  Standards can make on a procedureASTM E-1444
  requires DC yokes to have a lifting force of at
  least 30 lbs.(small spacing) and a 50 lbs. lift
  for a large spacing of legs.ASTM A-275 requires
  DC yokes have a lifting power of at least 40 lbs
  at 3 to 6" spacing of legs.The ASME Boiler Code
  requires a DC yoke to have at least 40 lbs of
  lift at the maximum pole spacing.
• There is a misconception in the 'field' that one
  can take a yoke and proceed with magnitizing an
  object by dragging the yoke along the object's
  surface. Wrong!!!

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• If you are dragging an AC yoke, you are in fact
  not magnetizing the object but rather you are
  doing a lovely job of DEMAGNETIZING the object.
  As in ASTM E-1444 above, paragraph 6.7.1.1,
  demagnetizing using a coil (yoke) by moving the
  object through........(which is what you are
  doing).To correctly magnetize an object,
  position the yoke and apply magnetizing force for
  2 - 5 seconds before moving the unit to the next
  position.So watch which specification and
  procedure is being applied to your project.

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Ultrasonic testing (UT)

• Ultrasonic testing (UT) is a method of
  determining the size and location of
  discontinuities within a component using high
  frequency sound waves.
• Sound waves are sent through a transducer into
  the material and the shift in time require for
  their return or echo is plotted.
• Ultrasonic waves will not travel through air
  therefore flaws will alter the echo pattern.

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ULTRA SONIC
oscilloscope
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• Equipments
• 1.Oscilloscope to generate and receive
  ultrasonic waves.
• 2. Cathode Ray Tube where the traveling
  distance and intensity of reflected wave are
  measured to locate and determine the size of the
  defect.
• 3.Vibrating Transducer (Probe)
• 3.1. Straight Beam
• 3.2. Angle Beam
• 4.Calibration Blocks to make time distance and
  built in holes and notches can be used as
  amplitude standards.
• DEFECTS DETECTED
• 1. Can locate all internal flaws located by other
  methods with the addition of exceptionally small
  flaws.
• ADVANTAGES
• 1. Extremely sensitive
• 2. Use restricted only by very complex weldments
• 3. Can be used on all materials
• DISADVANTAGES
• 1. Demands highly developed interpretation skill

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• Advantages
• Time to inspect fast response / ability to
  inspect from one side.
• B. Cost - 3,500.00 machine / 200.oo transducer
• Portable with battery pack
• Accuracy can locate small discontinuity
• Limitations
• Equipment
• Operator
• Standards
• Reports and records

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Radiographic Test (RT)

• Radiographic Test is a NDT that can detect
  surface and internal discontinuities using
  electro magnetic radiation of short duration by
  means of either
• 1. X-Ray
• 2. Gamma Ray
• It is a wave of energy that will pass through
  most materials and develop the negative image of
  what it passes through on film. Both of these
  methods are a danger to health
• 1. An X-Ray- Is electronically produced in a
  vacuum tube.
• 2. Gamma Ray-are emitted by the atomic decay.
• Two Common Source of Gamma Rays.
• Cobalt 60
• Iridium 192
• 3.FILM VIEWER
• Pictures taken are viewed as negatives will only
  give flat image not in three dimensional darkened
  area must be used for viewing.

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X- RAY
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X-RAY VIEWER

• Pictures taken are viewed as negatives
• will only give flat image not in three
  dimensional
• darkened area must be used for viewing

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• Advantages
• A Radiograph ( X-Ray picture) is a permanent
  record of a weld used for quality inspection
  purposes
• RT inspections can reveal flaws deep within a
  component

• Limitations
• The necessity to have access to both sides of the
  part being radiographed
• Unfavorable shape and orientation of some
  discontinuities.
• Radiation Safety requirements for personal
  protection.
• Tight Cracks, unless they are essentially normal
  to the radiation beam.
• Shallow tight surface cracks in thick sections
  usually can not be detected at all, even when
  properly oriented.
• Laminations are nearly impossible to detect
  because their orientation does not permit
  sufficient differences in the amount of radiation
  absorbed through the piece being examined to show
  the defect on film.

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Air or water pressure testing (LEAK TEST)

• Pressure testing or leak testing can be
  performed with either gasses or liquids.
• Voids that allow gasses or liquids to escape from
  the component can be classified as gross (large)
  or fine leaks.
• Extremely small gas leaks measured in PPM (parts
  per million) require a Mass Spectrometer to
  Sniff for tracer gases

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APPLICATION OF A LOAD

• Used to test pressure vessels
• Pipe lines
• The item for testing is filled with water or oil
  it is then pressurised using a pump
• A safety valve is set 1.5 to 2 times below the
  working pressure.

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PRESSURE TEST
Pressure Gauge
Pump
Test Specimen
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Quiz time

• True or False ?
• Dye penetrate inspections can only be used on non
  magnetic material.
• Answer False

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Quiz time

• True or False ?
• X-Rays can only be used to locate flaws at or
  near the surface of a weld.
• Answer False

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Quiz time

• True or False ?
• Virtually all welds have flaws.
• Answer True

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Quiz time

• True or False ?
• Magnetic particle testing can only detect flaws
  at or near the surface.
• Answer True

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Quiz time

• True or False ?
• Magnet particle testing can only be done on
  materials that can be magnetized.
• Answer True

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Quiz time

• The letters NDE Mean ___________ ?
• A nondestructive inspection
• B nondestructive evaluation
• C nondisruptive evaluation
• D nondestructive examination

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Quiz time

• The method most often used to check for leaks as
  small as one part per million (PPM) from a gas
  line or cylinder is the _________ Method ?
• A hydrostatic
• B mass spectrometer
• C soap suds bubble
• D scleroscope

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Modern WeldingYork County School of Technology