1
Q
Six steps in LPI
A
- preparation
- penetrant
- removal
- development
- inspect
- post clean
2
Q
Preparation
A
- remove all obstructions
- must not harm the test part
- do not leave residue that will affect the outcome of examination
3
Q
Penetrant
A
- application
- time critical
- appropriate type and method for relevant defects
- must not harm the part
4
Q
Methods of applying penetrant: (4)
A
- dipping
- spraying (electrostatic spray guns)
- brushing
- flowing
5
Q
Define Dwell Time
A
amount of time the penetrant is required to be in contact with the inspection surface
- penetrant must remain liquid
- immersion dwell time = soak time + drain time
6
Q
Removal
A
- excess penetrant is removed without removing penetrant in discontinuities
- water or solvent
- must not be harmful to part
7
Q
Removal methods (4)
A
A - water wash (emulsifiers in suspension)
B - Post emulsifiable, Lipophilic (oil base)
C - Solvent removal
D - Post emulsifiable, Hydrophilic (water base)
8
Q
Removal method A
A
- water wash
- emulsifiers in suspension
- best method of removal is with a coarse water spray
- risk of “over-washing”
- fluorescent, visible, dual
9
Q
What does “post emulsified” mean?
A
- removal method B & D
- emulsifiers are added after dwell time to make penetrant water washable
- fluorescent or visible
- time to work = emulsification time
10
Q
Removal method B
A
- post emulsifiable
- oil based
11
Q
Removal Method D
A
- post emulsifiable
- water based
- needs a mechanical scrub action (water spray)
- longer emulsification time than method B
12
Q
Removal method C
A
- solvent dampened cloth to wipe
- cloth is lint free
- fluorescent, visible, dual
- has classifications
13
Q
Solvent removal classes
A
1 - halogenated
2 - non-halogenated
3 - special application
14
Q
Develop
A
- “bleeds out” penetrant
- fine powder absorbs dye
- provides contrast
- develops or enhances the “see ability”
- blots dye to bring trapped penetrant to the surface
- spreads dye
- requires development time
15
Q
4 forms of developers
A
A - dry powder
B - water soluble
C - water suspendible
D - wet non-aqueous
16
Q
Inspect
A
- lighting (1000uW/cm2 black light, 1000 lux visible, 15in distance)
- finding indications
- understanding defects
- interpret and evaluate
17
Q
Post Clean
A
- neglecting can be harmful to part
- failure to remove will cause future contamination
- remove all remnant chemicals
