What is MPI and DPI?
Non-Destructive testing (NDT) is broad range of techniques used to analyse the properties of materials, parts and structures without damaging them. Common NDT methods include Magnetic Particle Inspection (MPI), Dye Penetrant Inspection (DPI), Ultrasonic Testing, Radiography and Eddy Current Testing.
Can MPI detect porosity?
Liquid penetrant (LPI) and magnetic particle (MPI) inspection techniques are methods that supplement visual inspection, revealing defects such as fine cracks or micro-porosity that would be invisible or difficult to detect by the naked eye.
What is the difference between dye penetrant and magnetic particle testing?
MPI has the capability to detect defects through thin coatings. Dye penetrant is less tolerant of poor surface condition and its effectiveness can also be adversely affected by any material within a defect. In addition MPI is much quicker to apply than dye penetrant.
What is MPI weld test?
Magnetic particle inspection (MPI) is one of the most widely used non-destructive testing methods for identifying both surface and near sub-subsurface defects on ferromagnetic pipe and pipe welds. After a magnetic field is introduced into the object, iron fillings are dusted onto the surface to be tested.
How do you carry out MPI?
Magnetic Particle Inspection is performed in four steps:
- Induce a magnetic field in the specimen.
- Apply magnetic particles to the specimen’s surface.
- View the surface, looking for particle groupings that are caused by defects.
- Demagnetize and clean the specimen.
What is dwell time in magnetic particle testing?
Penetrant dwell time is the total time that the penetrant is in contact with the part surface. The dwell time is important because it allows the penetrant the time necessary to seep or be drawn into a defect. Dwell times are usually recommended by the penetrant producers or required by the specification being followed.
What is the advantage of using DC in MPI?
| Current Type | Advantages |
|---|---|
| Direct Current (DC) -from DC generators and storage batteries | greater depth of penetration detects defects wholly below the surface field is uniform over part’s cross-section |
| Half Wave Direct Current (HWDC) single phase-from rectified AC sources | detects subsurface defects improved particle mobility |
Which metal can be tested by MPI?
Magnetic particle Inspection (MPI) is a nondestructive testing (NDT) process for detecting surface and shallow subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part.
Can you MPI Aluminium?
MPI equipment will only work on Ferromagnetic materials. Titanium, Nickle, Stainless Steel, Monel and Aluminium CANNOT be tested with MPI. You need to use Penetrant technique for that.
How do you test for MPI?
Magnetic Particle Inspection is performed in four steps..
- Induce a magnetic field in the specimen.
- Apply magnetic particles to the specimen’s surface.
- View the surface, looking for particle groupings that are caused by defects.
- Demagnetize and clean the specimen.
What is the principle of MPI?
The principle of the method is that the specimen is magnetised to produce magnetic lines of force, or flux, in the material. If these lines of force meet a discontinuity, such as a crack, secondary magnetic poles are created at the faces of the crack.
What is the acceptance criteria for MPI?
Code Acceptance Criteria for Magnetic Particle Inspection Rounded indication with size greater than 3/16 inches. Four or more rounded indications in a line separated by 1/16 inches or less. Crack-like indications, irrespective of surface condition.