Ndt For Weld Defects

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When the weld bead does not penetrate the entire thickness of the base plate. When two opposing weld beads do not interpenetrate. When the weld bead does not penetrate the toe of a fillet weld but only bridges across it.

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ë
 OF FUSION

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ëack of fusion, also called cold lapping or cold shuts, occurs when there is no fusion between the weld metal and the surfaces of the base plate.

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    UNDER
UTTING

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Undercutting is a defect that appears as a groove in the parent metal directly along the edges of the weld. It is most common in lap fillet welds, but can also be encountered in fillet and butt joints.

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   ›OROSITY

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›orosity is gas pores found in the solidified weld bead pores may vary in size and are generally distributed in a random manner. ›ores can occur either under or on the weld surface.

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R
ING

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Two Types - Hot crack &
old crack Hot cracks are those that occur while the weld bead is between the liquidus (melting) and solidus (solidifying) temperatures. Those cracks that occur after the weld bead has completely solidified are called cold cracks.

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OTHERS ~ ~ ~ ~ ~ ~ ~

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ëUSIONS EX
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ONVEX BE D ROOT
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VISU ë INS›E
TION ëIQUID DYE ›ENETR TION TEST M GNETI
› RTI
ëE TEST R DIOGR ›HI
INS›E
TION UëTR SONI
Fë W DETE
TION

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OUSTI
EMISSION TEST EDDY
URRENT TEST IN-SITU MET ëëOGR ›HY RE ë TIME X-R Y R DIOGR ›HI
INS›E
TION UëTR SONI
Fë W DETE
TION

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FIRST STE› FOR NON-DESTRU
TIVE INS›E
TION

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DETE
TS UNDER
UT, FIT-U› MISM T
H, S› TTERING ET
.

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GUIDES METHOD SEëE
TION OF OTHER NDT

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GIVES IDE ON SOUNDNESS OF WEëD

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Test to detect surface discontinuities in non-porous materials. In general, a liquid penetrant is applied evenly over the precleaned surface of the weld being tested and allowed to enter discontinuities.

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fter suitable dwelling time, the excess surface penetrant is removed and the weld dried.

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developer is then applied which draws the entrapped penetrant out of the discontinuity, staining the developer. The weld part is then inspected visually to determine the presence and absence of indications.

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  Easy to perform.
heap. Not dependent on dimensional intricacy. ll type of material, which is not porous, can be tested.

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Detect discontinuities that are exposed to surface only.
annot define the depth of defect. Sensitivity highly dependent on extent of surface cleaning.

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 à    Based on Type of ›enetrant Water Washable. ›ost-emulsifiable. Solvent-removable.

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Based on Type of Inspection ~ ~

Visible. Fluorescent.

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Test to detect surface and subsurface discontinuities in ferromagnetic materials.

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It is based on the principle that magnetic lines of force, when present in a ferro-magnetic material, will be distorted by a change in material continuity, such as a sharp dimensional change or a discontinuity.

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If the discontinuity is open to or close to the surface of a magnetized material, flux lines will be distorted at the surface, a condition termed ³FëUX ëE  GE´.

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When fine magnetic particles are distributed over the surface of the magnetized material while the flux leakage exists, they will be attracted in the place of flux leakage and the accumulation of the particles will be visible under the proper lighting condition.

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B SED ON TY›E OF M GNETIS TION DIRE
T ± where current is directly applied to the part to be tested to induce magnetic flux in the part. INDIRE
T ± where magnetic flux is introduced in the part using another magnet. B SED ON EXTENT OF M GNETIS TION FUëë ± where entire part is being magnetized at a time. › RT - where a portion of the part is magnetized at a time.

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B SED ON TY›E OF M GNETISING
URRENT
± where alternating current is used to magetize. HWD
± where half wave rectified current is used to magnetize. FWD
± where full wave rectified current is used to magnetize. ›ERM NENT ± where permanent magnet is used to magnetize.

~ ~

B SED ON EXTENT OF M GNETI
› RTI
ëE DRY ± where particles are applied in dry form. WET - where particles are applied in liquid suspension.

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B SED ON TIME OF INS›E
TION
ONTINUOUS ± where magnetization, particle application and inspection are carried out at a time. RESIDU ë ± where particle application and inspection are carried out after the magnetization force has been discontinued. B SED ON TIME OF INS›E
TION VISIBëE ± where inspections are carried out under normal light. FëUORES
ENT - where inspections are carried out under fluorescent light.

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an detect sub-surface discontinuities also. Wide variety, can be stationary and portable also. Independent on extent of surface cleaning.

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Detect discontinuities that are nearer to surface only.
annot define the depth of defect.
an not work on dia or para magnetic material.

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Test to detect internal discontinuities in non-porous materials. In general, radiation (X-ray or Gamma-ray) is penetrated on one side of the weld and radiographic films are fixed on the opposite side. Sufficient energy and time (based on type of material and thickness) is given to allow the radiation to penetrate and react the film placed on opposite side. The films are then processed and developed in the dark room to get planar image of the weld.

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X-R Y ± where X-Radiation is used to penetrate the weld.

~

G MM R Y ± where Gamma Radiation is used to penetrate the weld. In general, Iridium-192 and
obalt-60 isotopes are used to generate Gamma-ray.

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an detect internal discontinuities also.

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an be stationary and portable also.

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Independent on extent of surface cleaning.

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›ermanent radiographs can be stored for future reference.

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Hazardous, harmful to the health. Gives only planar image of the discontinuity, cannot define the depth of that. Slow process. ›oor sensitivity on higher thickness and dimensionally intricate job.

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6   à ~ Test to detect internal discontinuities in materials. ~ Ultrasonic waves are transmitted in a material by a probe along a pre-defined path. ~ ›art of the waves are reflected if any discontinuity comes in its wave path. ~ The reflected waves are again received by the probe and be analyzed. ~ The travel time and intensity of the reflected wave defines the discontinuity.

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6   à   B SED ON B SI
›RIN
IݑE ~ RESON N
E METHOD ± frequency of the sound pulse generated is continuously changed to detect the resonance frequency of the part tested. ~ THROUGH TR NSMISSION METHOD ± where the intensity of the ultrasound is measured after it has passed through the test piece. ~ ›UëSE E
HO METHOD ± where a sound pulse is transmitted in the test piece and the reflected waves are analyzed.

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6   à   B SED ON ›ROBE USED ~ NORM ë ›ROBE S
NNING ± where longitudinal sound waves are transmitted in the part tested in perpendicular direction of the surface and the same crystal is used as transmitter and receiver. ~ NGëE ›ROBE S
NNING ± where shear sound waves are transmitted in the part tested at a particular angle. ~ T-R ›ROBE S
NNING ± same as normal probe scanning but separate crystals act as transmitter and receiver.

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