What non-destructive inspection will find the most defects or discontinuities
Visual inspection
Visual Inspection steps before welding
- Review Certification papers for welders
- Set a plan for performing inspections and recording results
- Plan for identificatoin
- Inspect welding equipment to be used
- Inspect materials and configurations
- check base material
- Check weld filler materials
- Check joint preparation / Fit up (root opening angular alignment, planar alignment, groove angle
- Check cleaners of the weld zone
Visual Inspection steps DURING welding
- Visual examination of root pass
- Visual examination of individual weld passes
- Interpose cleaning
- Check interpose temp if required
If jigs, fixtures or tother alignment devices are used the welding inspector would check what?
to assure that they provide the proper alignment and that they are massive enough to maintain alignment
Pre heat inspection
Min & Max temps may be set
should be checked at a distance of not less than 3 inches away from the joint or the thickness of the base metal whichever is greater
can use indicator crayons, surface pyrometers, thermocouples, or surface thermometers
What to do if there is a root opening on a fillet weld
some standards require an increase in weld size by the out of the root opening which is present to provide the necessary weld cross section
Backstepping
- Method used to reduce distortion
- The direction of travel for the Individual passes is opposite that for the general progression of welding along the weld axis.
- Each subsequent weld pass seats ahead of the previous pass and progresses toward it
Visual Inspection steps After welding
-assure that all proceeding steps have been performed
-measurement of the weld to determine its size is correct
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Measurement of groove welds
- Primarily concerned if the weld groove is filled flush with the base metal surface without excessive reinforcment
- Any undersell must be corrected by depositing additional weld metal
Measurement of fillet welds
- Size determination is accomplished with the aid of fillet weld gauges
- The weld size is determined by the size of the largest isosceles right triangle which can be contain in the welds cross section
- Determine if the weld is concave or convex (if not apparent use both gages to decide size
Measurement of fillet welds (Convex)
the leg size dimensions are the same
Measurement of fillet welds (Concave)
will be sized based on the throat dimension
If unequal fillet weld legs the size will be governed by…
the shorter of the two legs
PT Type of discontinuities Essential elemete Types Advantages / Disadvantages
Penetrant Test
- Surface discontinuities
- Bleeding out of penetrating medium against a contrasting colored background developer
- Visible / Fluorescent
ADVANTAGES - not limited to metal / can be used on dissimilar metal joints / can be applied to non magnetic materials / portable / minimal equipment
LIMITATIONS - no detection of subsurface issues / time consuming / and cleaning up
MT Type of discontinuities Essential elemete Types Advantages / Disadvantages
Magnetic Particle Test
Surface discontinuities / minimal indication of near surface issues
Creating a magnetic field in a part and applying ion particles onto test surface
TYPES - AC Strongest / DC / YOKE (longitudinal)
- Longitudinal - coiled electrical conductor - “coil shot”
- Circular magnetism - “head shot” - test piece becomes ht electrical conductor used to find longitudinal flaws
ADVANTAGES
- Rapid testing / low cost / portable / good for surface discontinuities
LIMITATIONS
- Demagnification after testing
- Cant use on Austenitic stainless steel, aluminum, coper, - Cant use on metal that can’t be magnetized
- Electricity needs may limit portability
- Rough surfaces make test harder
RT Type of discontinuities Essential element sources Advantages / Disadvantages
RADIOGRAPHIC TESTING
Subsurface discontinuities which have diff. densities than the material being radiated. Such as
- VOIDS, POROSITY, (dark spots on film)
- METALLIC INCLUSIONS (produce light areas on film)
Radiation that passes through the test subject will form a contrasting image on the film receiving the radiation.
RADIOGRAPHIC SOURCES
- Iridium, Cesium, cobalt, gamma, x-ratys
- Normal resolution sensitivity is 2%
ADVANTAGES
- gives permanent records / subsurface view / most materials can be tested /
LIMITATIONS
- human hazard / radiation safety / evacuation cause delays / expensive / competent operators / need access to both side of the test piece * may not detect cracks and Incomplete fusion
UT Type of discontinuities Essential elemete Types Advantages / Disadvantages
Ultrasonic Test
Surface and subsurface flaw detection
(laminations, cracks, incomplete fusion, inclusions, voids, soundness determinations, thickness measurements)
uses high frequency sound waves to measure geometric and physical properties in materials
Voltage is converted by transducer to mechanical energy in the form of sound waves. (piezoelectric effect)
There will always be an initial indication called a MAIN BANG.
types of ultrasonic transducers
LONGITUDINAL WAVES & STRAIGHT BEAM -used for material thickness and flaw depth
SHEAR & ANGLE WAVES - are used for weld valuation cause it can be sent in at an angle
Two types of testing
- contact (uses couplant liquid as a medium - oil, grease, glycerin, water, cellulose powder, cornstarch with water)
- immersion (placed underwater)
ADVANTAGES
- volumetric test / can tell you the depth of the flaw beneath the surface / one need access to one side / can detect critical flaws / deep penetration -200 in in steel / very accurate / lightweight / battery powered / portable / hand held / can save results on digital display
LIMITATIONS
Required high skill / test object surface must me smooth / limited to groove welds that are thicker than 1/4 in
ET - other name? Type of discontinuities Essential elemete Types Advantages / Disadvantages
Eddy Current test (electromagnetic testing)
Can detect thickness, electrical conductivity, magnetic permeability, hardness, heat treatment conditions
cracks, seams, laps, voids, and inclusions near the test object’s surface.
An AC current brought near a metal specimen will create an electromagnetic induction.
ADVANTAGES
- can be automated / prob need not touch the test object / assembly line inspection possible / can inspect hot areas die to no touching / can be used on electrically conductive material magnetic or non magnetic.
LIMITATIONS
- required skilled operator to calibrate and read results
- has to be used on conductive materials
- Maximum penetration os shallow (3/16 of an inch or less)
- Standards are elaborate and numerous
- Surface contamination that is conductive can cause problems
- may require special probes and techniques
Penetrant Test process in detail
- Clean Surface
- penetrant allowed to remain on the surface (dwell time)
- penetrant drawn in to the surface by capillary action (5-30min)
- Remove excess penetrant with lint free cloth & solvent and white in one direction
- Apply THIN UNIFORM layer of developer which draws the remaining penetrant from discontinuities.
capillary action
phenomenon that causes liquid to be drawn into tight clearances
AET ET LT MT NRT PT PRT RT UT VT
Acoustic Emission Eddy Current Leak Magnetic Particle Neutron Radiographic Penetrant Proof Radiographic Ultrasonic Visual
piezoelectric effect
Voltage is converted by transducer to mechanical energy in the form of sound waves. (USED FOR UT)
