1
Q
What is a developer?
A
- fine powder that absorbs the dye
- provides contrast
- “bleed out” action
- enhances “see ability”
2
Q
How does developer enhance the visibility of indications?
A
- blots dye bringing more back to surface
- spreads dye making indications appear larger
- contrast
3
Q
What is a Developer time?
A
time it takes the developer to blot the penetrant (reverse capillary action)
ASTM E165 = 10 minutes
4
Q
Describe development times
A
dwell times 20min or greater, development time is = 1/2 dwell time
- maximum time for aqueous developers is 2 hours
- maximum time for non-aqueous = 1 hour
5
Q
Types of developers
A
A - dry powder
B - water soluble
C - water suspendible
D - wet non aqueous
6
Q
Dry powder devloper
A
- as sensitive as water soluble
- same job as water based
- article must be dry
- drying time and temp must be controlled, do not overheat
- air soluble
- air suspendible
7
Q
Application of dry developers
A
- dusting
- dust chamber
- dipping
- spraying
8
Q
Water based developers
A
- suspendible (mix with water but don’t dissolve)
- soluble (particles dissolve)
- time needed for water to evaporate
- forced air ovens, but do not overheat
- require proper storage
9
Q
Application of Water based developers
A
- dipping
- pouring
- spraying
done in production line or lab
applied after washing stage (emulsified or water wash)
10
Q
Wet Non-Aqueous Developers
A
- powder held in suspension with a non aqueous fluid
- often an alcohol base
- alcohol thins penetrant viscosity and speeds up blotting effect thus increasing sensitivity
- most sensitive
- solvent action brings more penetrant to surface
- often used with solvent removable
11
Q
Application of Wet Non-aqueous developers
A
- applied to dry surface
- even, light coats
- white light
- time for alcohol to evaporate and apply another coat
12
Q
Properties required of developers
A
- absorb penetrant
- disperse dye to make indications bigger
- fine grainer to retain sharp definition
- mask background discontinuities
- provide contrast
- easily applied
- must not fluoresce
- easily removable
- not harm part
- not harm inspector
13
Q
Drying in LPI
A
- blast of cold air (remove water only)
- ambient air temperature
- forced hot or cold air
14
Q
Drying oven requirements
A
- thermostatically controlled
- air no >71°C
- part no > 10°C to 38°C (fluorescent)
- part no >10°C to 52°C (visible)
Per ASTM E165
