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. Introduction.
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Upon completion of this module you will be able to:
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.
A. Usually inexpensive - the majority of expense will be in the inspector’s wage.
B. Equipment is small and inexpensive – there’s 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 inspection
IV. Five steps of Visual Inspection.
V. Equipment required.
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.
Measuring Steel Rule
Fillet Weld Gauge
Palm Weld Gauge
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.
Welder Inspect before welding
- Root Face
- Root Gap
- Bevel Angle
- Joint and Fit up
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 welding
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.
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.
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 company’s 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 manufacturer’s 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.
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.
Defects open to surface only – Cracks, slag inclusion, porosity and undercuts.
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
Red Dots will appear if Defect is present. Very Red Color the defect is deep and not very red the defect is shallow.
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.
OBJECTIVE:Upon completion of the module, you will be able to;1. Describe Magnetic Particle Testing and its limitations.2. Perform Magnetic Test
1. Iron Particle, wet or dry or flourescent
2. Special power source
3. Ultraviolet light for the flourescent type
1. Surface and near surface discontinuities
4. Slag Inclusions
5. Incomplete Fusion
1. Detects discontinuities not visible to the naked eyes
2. Useful in checking edges prior to welding and repairs
3. No size restrictions
1. Used in magnetic materials only
2. Surface roughness may distort magnetic field
3. Normally no permanent record
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.
- 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 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.
The YOKE method which uses an electromagnet
Two types of magnetic particles:
Methods of particle application:
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.
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 126.96.36.199, 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.
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.
1. Can locate all internal flaws located by other methods with the addition of exceptionally small flaws.
1. Extremely sensitive
2. Use restricted only by very complex weldments
3. Can be used on all materials
1. Demands highly developed interpretation skill
1. An X-Ray- Is electronically produced in a vacuum tube.
2. Gamma Ray-are emitted by the atomic decay.
Pictures taken are viewed as negatives
will only give flat image not in three dimensional
darkened area must be used for viewing
A: nondestructive inspection
B: nondestructive evaluation
C: nondisruptive evaluation
D: nondestructive examination
B: mass spectrometer
C: soap suds bubble