Inspection
The following are general steps for inspecting on a wet horizontal machine:
- Part is cleaned of oil and other contaminants
- Necessary calculations done to know the amount of current required to magnetize the part. See ASTM E1444/E1444M for formulas.
- The magnetizing pulse is applied for 0.5 seconds during which the operator washes the part with the particle, stopping before the magnetic pulse is completed. Failure to Stop prior to end of the magnetic pulse will wash away indications.
- UV light is applied while the operator looks for indications of defects that are 0 to +/- 45 degrees from path the current flowed through the part. Indications only appear 45 to 90 degrees of the magnetic field applied. The easiest way to quickly figure out which way the magnetic field is running is grab the part with either hand between the head stocks laying your thumb against the part (do not wrap your thumb around the part) this is called either left or right thumb rule or right hand grip rule. The direction the thumb points tell us the direction current is flowing, the Magnetic field will be running 90 degrees from the current path. On complex geometry like an engine crank the operator needs to visualize the changing direction of the current and magnetic field created. The current starts at 0 degrees then 45 degrees to 90 degree back to 45 degrees to 0 then -45 to -90 to -45 to 0 and repeats this for crankpin. So inspection can be time consuming to carefully look for indications that are only 45 to 90 degrees from the magnetic field.
- The part is either accepted or rejected based on pre-defined accept and reject criteria
- The part is demagnetized
- Depending on requirements the orientation of the magnetic field may need to be changed 90 degrees to inspect for indications that can not be detected from steps 3 to 5. The most common way to change magnetic field orientation is to use a Coil Shot. In Fig 1 a 36 inch Coil can be seen then steps 4, 5, and 6 are repeated
Read more about this topic: Magnetic Particle Inspection
Famous quotes containing the word inspection:
“Thus the orb he roamed
With narrow search, and with inspection deep
Considered every creature, which of all
Most opportune might serve his wiles, and found
The serpent subtlest beast of all the field.”
—John Milton (1608–1674)
“Utopias are presented for our inspection as a critique of the human state. If they are to be treated as anything but trivial exercises of the imagination. I suggest there is a simple test we can apply.... We must forget the whole paraphernalia of social description, demonstration, expostulation, approbation, condemnation. We have to say to ourselves, “How would I myself live in this proposed society? How long would it be before I went stark staring mad?””
—William Golding (b. 1911)
“We had an inspection today of the brigade. The Twenty-third was pronounced the crack regiment in appearance, ... [but] I could see only six to ten in a company of the old men. They all smiled as I rode by. But as I passed away I couldn’t help dropping a few natural tears. I felt as I did when I saw them mustered in at Camp Chase.”
—Rutherford Birchard Hayes (1822–1893)