DYE PENETRANT INSPECTION

Type of operation.
Manual or mechanised.

Equipment.
Minimum - aerosols containing dye, developer, cleaner.
Maximum - Tanks, work handling gear, ultra-violet lamp.

Mode of operation.
A special dye is applied to the surface of the article to be tested. A suitable time interval allows it to soak into any surface defects. The surface is then freed from surplus dye and the dye in the crack revealed by either: applying a white powder developer into which the dye is absorbed producing a colour indication,or, illuminating with ultra-violet light under which the dye fluoresces, that is, emits visible light. This must be done where normal lighting is subdued.

Operating parameters.
Portability : excellent (for aerosols)
Access : good
Minimum defect size : 0.025 mm wide
Time : 30 minutes approx.

Materials.
Any - non porous.

Typical welding applications.
Root runs in pipe butt welds.
Leak paths in containers.


Overall advantages.
Low cost.
Direct indication of defect location.
Initial examination by unskilled labour.

Overall limitations.
Surface defects only detected.
Defects cannot readily be rewelded due to trapped dye.
Rough welds produce spurious indications.

Safety.
Dye and propellant gases have low flash points.