Basics Flashcards
how small of a discontinuity can be detected?
1 nanometre (nm)
principle that enables pt to work?
capillary action
why are oil based penetrants used?
due to oils low surface tension
what is surface tension?
atoms that bind the surface of a liquid
Tracer dye type 1
fluorescent
Tracer dye type 2
visible
tracer dye type 3
dual
Max white light in darkened area
20 lx | 2 fc
black light intensity
1000 mw @ 15”
brightness for visible / colour contrast?
1000lx (100fc)
what does each method classify?
the method in which the excess penetrant must be removed from the part
method A
water washable
method B
post emulsifiable - lipophilic
method C
solvent removable
method d
post emulsifiable - hydrophilic
how is method A penetrant removed?
water
how is method b/d penetrant removed?
emulsifier is added to render it water washable
how is method c penetrant removed?
solvent moistened cloth
how does lipophilic emulsifier work?
mixes with the penetrant to make it water washable (chemical reaction)
how does hydrophilic emulsifier work?
reduce the surface tension (mechanical process)
3 water wash advantages
1) penetrant easily removed from rough surfaces
2) cheap
3) fast
3 water wash disadvantages
1) 3x longer dwell
2) X smooth surfaces
3) X wide and shallow disc.
4 post-emulsifiable advantages
1) smooth surfaces
2) wide/shallow disc.
3) highest sensitivity
4) short dwell
2 post-emulsifiable disadvantages
1) $
2) additional time for emulsification
2 solvent removable advantages
1) remote inspection
2) simple
2 solvent removable disadvantages
1) hard to remove excess penetrant
2) ventilation
2 types of developer
dry or wet
2 dry powder advantages
1) rough surfaces
2) cheap
1 dry powder disadvantage
low sensitivity
highest sensitivity penetrant
post-emul
most sensitive developer
non-aqueous
6 steps of pt
1) preclean
2) apply penetrant
3) removal of penetrant
4) developer
5) inspection
6) post clean
detergent cleaning
remove light oil / grime
solvent cleaning
portable - remove oil / grease
alkaline cleaning
stationary - most effective for oil / grease
steam cleaning
oil / grease
ultrasonic cleaning
grime / tarnish