Objective 09: Radiographic Testing Flashcards
What kinds of flaws does Radiographic Testing reveal?
Flaws that are internal or on an inside surface
What kind of images does Radiographic Testing produce nowadays
Filmless radiography captures an image, digitally enhances it, and sends the image anywhere in the world
What is the benefit of Radiographic Testing producing digital images?
They don’t deteriorate with time
What is the state of equipment nowadays used for Radiographic Testing?
They use small, light, and portable equipment that produces high-quality x-rays. Linear acceletators generate extremely short wavelength, highly penetrating radiation.
What principle is Radiographic Testing based on?
In the presence of flaws there is a differential absorption of penetrating radiation. Variations in density, composition and thickness result in the component being radiographed while absorbing different amounts of penetrating radiation.
What is the basic procedure of Radiographic Testing?
- Unabsorbed radiation passes through the test component and exposes a film
- The exposed film indicates the varying amounts of radiation passing through the component and gives a permanent record of test
What source of radiation is used to produce X-rays for Radiographic Testing?
X-rays are produced by high-speed electrons striking a metal target, causing a transfer of energy. An X-Ray tube in an x-ray machine produces the high-speed electrons.
What source of radiation is used to produce X-rays for Radiographic Testing?
X-rays are produced by high-speed electrons striking a metal target, causing a transfer of energy. An X-Ray tube in an x-ray machine produces the high-speed electrons.
What source of radiation is used to produce Gamma Rays for Radiographic Testing?
Gamma rays are emitted from radioisotopes, e.g. Cobalt 60 and Iridium 192, as they decay
What are some applications of Radiographic Testing in the pressure equipment industry?
- If something is inside a pressure component
- Material thickness measurements to help determine corrosion rates
- Testing of welds
What discontinuities can be revealed by Radiographic Testing?
- Voids
- Porosity
- Incomplete Penetration
- Cupping
- Incomplete fusion
- Internal Bursts
- Thickness variations
- Corrosion, thinning and pitting
- Shrinkage cracks
- Slag inclusions
What discontinuities can be revealed by Radiographic Testing?
- Voids
- Porosity
- Incomplete Penetration
- Cupping
- Incomplete fusion
- Internal Bursts
- Thickness variations
- Corrosion, thinning and pitting
- Shrinkage cracks
- Slag inclusions
What are the 4 essential steps to completing Radiographic Testing?
- Source Selection
- Set-Up
- Exposure of test component to the radiation source
- Film development
What are the 4 essential steps to completing Radiographic Testing?
- Source Selection
- Set-Up
- Exposure of test component to the radiation source
- Film development
How much time is devoted to Set-Up for Radiographic Testing?
60%
Why is so much time devoted to Set-Up for Radiographic Testing?
Radiographic Testing requires constant attention to safety. Large doses of x-rays or gamma rays kill human cells and massive doses can cause severe dsability or death. Safety is a concern for both operators and anyone else in areas where Radiographic Testing is used.
How do workers measure their exposure to radiation?
By wearing a Dosimeter clipped to their clothing
How do workers measure their exposure to radiation?
By wearing a Dosimeter
Dosimeter
A pen shaped device that measures the cumulative dose of radiation it receives
What are the main components of a Dosimeter?
- Ionization chamber which is sensitive to radiation
- Quartz fibre electrometer to measure the charge
- Microscope to read the shadow of the fibre on a reticle
What is the composition of the reticle of a Dosimeter?
It consists of a network of dots, wires, crosshairs or fine lines in the focal plane of an optical instruments eyepiece
What is the composition of the electrometer of a Dosimeter?
It contains 2 electrodes, one of which is a movable quartz fibre
What is the intial state of the electrometer of a Dosimeter?
It is charged to a predetermined voltage which causes its electrodes to assume a calibrated separation
How is the reading from a Dosimeter read?
Illumination for the optical system is obtained by pointing the dosimeter at any convenient light source. Light passes through the clear glass bottom seal to illuminate the reticule
How is a Dosimeter charged?
An insulated charging pin is contained in the bellows. When charging, the charging pin moves up to contact the electrometer, thereby closing the circuit. Sufficient voltage is applied to recharge the system.
What factors are considered when selecting a Radiographic Testing technique?
- The size and geometry of the component being tested
- Typical defect type, size, location, and orientation
- Whether shop or field testing is necessary
- Assurance of personnal safety
- Size of discontinuity anticipated
- Whether both sides of the component can be accessed as this is required to place the film
How large must flaws be in order to be detected by Radiographic Testing?
At least as large as 2% of the penetration thickness
What are the 3 basic steps to interpreting radiographs from Radiographic Testing?
- Detection
- Interpretation
- Evaluation
What does interpretaion of radiographs require from the radiographer?
Visual acuity
Visual Acuity
The ability to detect a spatial pattern in an image
What 2 factors aid a radiographers visual acuity?
- Lighting condition in the place of viewing
2. Experience level for recognizing various features in the image
Which discontinuities are typical of all types of welding?
- Cold Lap
- Porosity
- Cluster Porosity
- Slag Inclusions
- Incomplete Penetration (IP)/Lack of Penetration (LOP)
- Incomplete Fusion
- Internal Concavity/Suck Back
- Internal or Root Undercut
- External or Crown Undercut
- Offset or Mismatch
- Inadequate Weld Reinforcement
- Excess Weld Reinforcement
- Cracking
Cold Lap
Condition where the weld filler metal does not properly fuse with the base metal or the previous weld pass material (interpass cold lap). The arc does not melt the base metal sufficiently and causes the slightly molten puddle to flow into the base material without bonding.
Porosity
Void in the material due to gas entrapment in the solidifying metal which has a radiographic density more than the surrounding area and often appears as dark round or irregular spots or specks appearing singularly, in clusters or rows.
Wormhole Porosity
Porosity that results from gas attempting to escape while the metal is still in a liquid state and appears elongated with a tail
Cluster Porosity
Porosity that is caused when flux coated electrodes are contaminated with moisture that turns into gases when heated and then become trapped in the weld during the welding process. It appears like regular porosity in the radiograph, but the indications are grouped close together.
Slag Inclusions
Non-metallic solid material entrapped in a weld metal or between weld and base metal that appear as dark, jagged asymmetrical shapes within the weld or along the weld joint areas on radiographs
Incomplete Penetration (IP)/Lack of Penetration (LOP)
Lack of penetration which occurs when the weld metal fails to penetrate the joint and creates a stress riser from which a crack may propagate. On a radiograph it appears as a dark area with well-defined, straight edges that follows the land (root face) down the centre of the weldment
Incomplete Fusion
Condition where the weld filler metal does not properly fuse with the base metal and appears as a dark line or lines oriented in the direction of the weld seam along the weld preparation or joining areas.
Internal Cavity/Suck Back
Condition where the weld metal has contracted as it cools and has been drawn up into the root of the weld and looks on a radiograph similar to lack or penetration but with irregular edges and often quite wide in the centre of the weld image
Internal or Root Undercut
Erosion of the base metal next to the root of the weld which appears on the radiographic image as a dark, irregular line offset from the centerline of the weld
External or Crown Undercut
Erosion of the base metal next to the crown of the weld and appears on the radiograph as a dark irregular line along the outside edge of the weld area
Offset or Mismatch
Condition where 2 pieces being welded together are not properly aligned and on the radiographic image, there is a noticeable difference in density between the 2 pieces
Inadequate Weld Reinforcement
Area of a weld where the thickness of weld metal deposited is less than the thickness of the base material. This area appears darker on a radiograph than the surrounding base material
Excess Weld Reinforcement
An area of a weld that has weld metal added in excess of what is specifyed by engineering drawings and codes and that appears as a localized, lighter area of the weld.
How does Cracking appear in radiographs?
It can only be detected if the crack is propogating in a direction that produces a change in thickness parallel to the x-ray beam and appears as jagged and often very faint irregular lines
What discontinuities are peculiar to TIG Welds?
- Tungsten Inclusions
2. Oxide Inclusions
How do Tungsent Inclusions occur?
- Tungsten electrode accidentally contacts the weld puddle
- Tungsten electrode contacts the filler rod
- Current settings are excessive, causing the tungstem electrode to overheat
- Electrode is improperly installed in the gun
- Electrode is damaged (internal cracks)
- Improper shielding gas is used
- Shielding gas supply is interuppted or inadequate
How does Tungsten Inclusion appear on a radiograph?
Since tungsten is denser than aluminum or steel, it appears as a lighter area with a distinct outline
Oxide Inclusion
Usually visible on the surface of material being welded and, due to being less dense than the surrounding materials, appear as dark, irregularly shaped discontinuities
