WELDING INSPECTION AND QUALITY CONTROLUpon 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.

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)

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. AdvantagesA. 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.

C. No powered required this makes VT the most portable NDT process.D. Can avoid defects and costly repairs by able to make intermittent inspectionII. DISADVANTAGESRequires 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.

IV. Five steps of Visual Inspection.Inspection practice establish a definite procedure to insure adequate and consistent coverage.Inspection prior to weldingInspection during weldingInspection after weldingMarking and making repairsV. 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.

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 materila type.VI. Inspection Before WeldingDrawing 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?

E. MaterialDid 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. AssemblyInspect 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.

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.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.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 weldingThe applicable code or standard it will list acceptance standards They will generally cover the following areas;Weld size use gages to check conformance to printsContour 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.

4. Overlap it is an indication of lack of fusion5. Undercut if allowed how much?6. Spatter what is excessive?IX. Making repairsA. 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.

Visual Inspection (VT)Visual is the most common inspection methodVT reveals spatter, excessive buildup, incomplete slag removal, cracks, heat distortion, undercutting, & poor penetration Typical tools for VT consist of Fillet gauges Magnifying glasses, Flashlights, & Tape measures or calipers.

VT Visual TestBefore welding- Root Face- Root Gap- Bevel Angle- Joint and Fit up

VISUALWhile welding The rate the electrode meltsThe way the weld metal flowsSound of the arcThe light given of

After weldingUnder cut Lack of root fusionAny pin holes from gas or slagAmount of spatterDimensions of weldVT Visual Test

Visual Inspection (VT)Fillet gauges measure The Legsof the weld Convexity(weld rounded outward) Concavity(weld rounded inward)Flatness

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.

DYE PENETRANTSThese are an aid to visual inspection1. Cleaner Solvent2. Penetrant3. DeveloperWill only find surface defectsUse correct type

Process Principle 6 stepsSurface preparationPenetrant applicationExcess penetrant removalDeveloper applicationInspection / evaluationPost cleaning

DYE PENETRANTSTypesRed Flouresant

CAUTIONOil basedWater washable

DYE PENETRANTS

DETECTION

II. Application:Ferrous and non ferrous materialsPlastic and glass ceramics-insulators-anything that is nonporousIII. Advantages:Low costEase 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 onlyCan not be used on porous or absorbent materialsV. Safetya. 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.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 type2. 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 conditions1. Use normal lighting for inspection 2. considered to be less expensive. 3. Simplest to use. 4. Easy to use for field work5. no electric power required

Dual sensitivity works both fluorescent and visible.VII. ApplicationFollow Approved ProcedureClean and dry the surface. - Solvent cleaner2. Apply penetrant (brush, spray or dip) penetrant power comes capillary action3. Penetration time -minimum dwell time is 5-20 minutes3. Remove excess penetrant.- when using solvent type, put solvent on a cloth not on the part- excess penetrant will give false indications4. 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.

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 ComparatorIdeal 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.

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.

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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.

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) SNSNSNSNSNSNSNSNSNSNSNSNNSFig. A

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 patternWidth of defect

To enable the formation o 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.Two types of magnetic particles:Fluorescent typeNon 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.

MAGNETIC PARTICLEMainly for surface defectsSome sub surface defects can be foundOnly ferrous metal

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.

ULTRA SONICoscilloscope

Advantages:Time to inspect fast response / ability to inspect from one side.B. Cost - $3,500.00 machine / $200.oo transducerPortable with battery packAccuracy can locate small discontinuity

Limitations:EquipmentOperatorStandardsReports and records

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 either1. X-Ray2. 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 60Iridium 192 3.FILM VIEWERPictures taken are viewed as negatives will only give flat image not in three dimensional darkened area must be used for viewing.

X- RAY

X-RAY VIEWERPictures taken are viewed as negativeswill only give flat image not in three dimensionaldarkened area must be used for viewing

Limitations:The necessity to have access to both sides of the part being radiographedUnfavorable 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. Advantages:A Radiograph ( X-Ray picture) is a permanent record of a weld used for quality inspection purposesRT inspections can reveal flaws deep within a component

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

APPLICATION OF A LOADUsed to test pressure vesselsPipe lines The item for testing is filled with water or oil it is then pressurised using a pumpA safety valve is set 1.5 to 2 times below the working pressure.

PRESSURE TESTPressure GaugePumpTest Specimen

Quiz time True or False ?

Dye penetrate inspections can only be used on non magnetic material.

Answer: False

Quiz time True or False ?

X-Rays can only be used to locate flaws at or near the surface of a weld.

Answer: False

Quiz time True or False ?

Virtually all welds have flaws.

Answer: True

Quiz time True or False ?

Magnetic particle testing can only detect flaws at or near the surface.

Answer: True

Quiz time True or False ?

Magnet particle testing can only be done on materials that can be magnetized. Answer: True

Quiz time The letters NDE Mean ___________ ? A: nondestructive inspection B: nondestructive evaluationC: nondisruptive evaluation D: nondestructive examination

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

Modern WeldingYork County School of Technology