Questions and Answers
What is the primary purpose of demagnetizing a test piece before magnetic particle inspection?
Which of the following is NOT a type of magnetic particle used in magnetic particle inspection?
What is the primary function of a magnetizing unit in magnetic particle inspection?
Which of the following is a common acceptance criteria used in evaluating indications in magnetic particle inspection?
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What is the primary purpose of surface preparation before magnetic particle inspection?
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Which of the following methods is commonly used for demagnetization of test pieces?
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What is the difference between a relevant indication and a non-relevant indication in magnetic particle inspection?
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What is the primary purpose of a magnetic particle inspection procedure?
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Which of the following is NOT a typical element of a magnetic particle inspection procedure?
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Why is the direction of the magnetic field important in magnetic particle inspection?
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Study Notes
Magnetic Field Principles
- Magnetic Fields: Created by the interaction of magnetic fields and magnetic poles
- Magnetic Lines of Force: Continuous loops that emerge from the north pole and enter the south pole
- Magnetic Flux: The amount of magnetic field that passes through a given area
- Magnetic Field Strength: Measured in oersteds (Oe) or tesla (T)
- Magnetic Field Direction: Important for MP testing, as it affects the formation of indications
Test Medium And Equipment
- Magnetic Particles: Finely divided iron oxide particles suspended in a liquid carrier
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Types of Magnetic Particles:
- Dry powder
- Wet suspension
- Fluorescent
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Equipment:
- Magnetizing units (yokes, coils, etc.)
- Power sources
- Particle applicators (spray guns, etc.)
- UV lamps (for fluorescent particles)
Surface Preparation And Demagnetization
- Surface Preparation: Cleaning and degreasing the test surface to ensure particle mobility
- Demagnetization: Reducing the residual magnetism in the test piece to prevent interference with the test
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Demagnetization Methods:
- Alternating current (AC) demagnetization
- Direct current (DC) demagnetization
- Thermal demagnetization
Indication Interpretation And Evaluation
- Indications: Visible signs of magnetic particle accumulation at defect sites
-
Indication Types:
- Relevance: Cracks, porosity, lack of fusion, etc.
- Non-relevance: Oil, dirt, scratches, etc.
- Evaluation Criteria: Size, shape, location, and intensity of indications
- Acceptance Criteria: Specified in codes and standards (e.g., ASME, AWS)
Procedure Development And Execution
- Procedure Development: Establishing a written procedure for the specific test
-
Procedure Elements:
- Test object preparation
- Magnetization technique
- Particle application
- Inspection and evaluation
- Execution: Following the developed procedure to ensure consistent and reliable results
Magnetic Field Principles
- Magnetic fields arise from the interaction between magnetic poles.
- Magnetic lines of force are continuous, emerging from the north pole and returning to the south pole.
- Magnetic flux measures the quantity of magnetic field passing through a designated area.
- Magnetic field strength is quantified in oersteds (Oe) or tesla (T).
- Understanding magnetic field direction is crucial for magnetic particle testing, influencing the formation of indications.
Test Medium And Equipment
- Magnetic particles consist of finely divided iron oxide suspended in a liquid medium.
- Types of magnetic particles available include dry powder, wet suspension, and fluorescent variants.
- Essential equipment includes magnetizing units (like yokes and coils), power sources, and particle applicators (such as spray guns).
- UV lamps are utilized when working with fluorescent magnetic particles for enhanced visibility.
Surface Preparation And Demagnetization
- Proper surface preparation entails cleaning and degreasing to facilitate particle movement.
- Demagnetization diminishes residual magnetism to eliminate interference during testing.
- Methods for demagnetization include alternating current (AC), direct current (DC), and thermal techniques.
Indication Interpretation And Evaluation
- Indications are visible accumulations of magnetic particles that highlight defect locations.
- Indication types include relevant (e.g., cracks, porosity, lack of fusion) and non-relevant (e.g., oil, dirt, scratches).
- Evaluation criteria for indications encompass size, shape, location, and intensity.
- Acceptance criteria for indications are defined within industry codes and standards such as ASME and AWS.
Procedure Development And Execution
- Developing test procedures involves creating comprehensive written guidelines tailored to specific tests.
- Key elements of the procedure cover test object preparation, magnetization methods, particle application, and inspection evaluation.
- Adhering to the established procedure ensures consistent results and reliability in testing outcomes.
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Description
Test your understanding of magnetic fields, lines of force, flux, and field strength and direction.
