Liquid penetrant testing Flashcards
1
Q
What type of defects can liquid penetrant testing detect?
A
surface defects on non-porous materials, like voids, cracks and other discontinuities
2
Q
What are the steps of liquid penetrant testing?
A
- Part has to be perfectly cleaned
- The liquid penetrant is applied to the surface and left in order to penetrate the cracks and defects
- Capillarity action draws the liquid inside the openings (even against gravity)
- Excess liquid is removed
- A developer (powder) that can absorb the penetrant is applied
- The high contrant between the liquid and the developer helps locate the defect.
3
Q
What are some qualities of the penetrant in liquid penetrant testing?
A
- Good wettability
- Good capillarity
- Evaporate slowly and not dry to quickly
- chemically inert
- Nontoxic
- Easily to remove ftom the surface of part
4
Q
What are the classifications of penetrants based on removing of the excess penetrant?
A
- Solvent removable penetrants: removed by wiping with a damped cloth with solvent
- Water washable penetrants: removed with a course spray of water
- Post-Emulsifiable penetrants: water washeble only after they have reacted with an emulsifier solution
5
Q
What is the role of the developer in liquid penetrant testing?
A
To pull trapped penetrant out of defects and to spread it out on the surface so that it can be seen.
6
Q
What are the advantages of liquid penetrant testing?
A
- Can be applied to almost all solid materials
- Very simple equipment is required
- It has a high sensitivity to surface discontinuties of small size
7
Q
what are the disadvantages of liquid penetrant testing?
A
- Part needs to be non-porous
- Needs carefully cleansing and degreasing
- Roughness should not exceed specific limits
- Presence of coating is not compatible
- Only surface flaws can be detected
- If surface flaws are filled with dirt etc, they will not be detected
- It gives no indication about the size of the defect
