2.2.1
LIQUID PENETRANT
TESTING:-
Penetrant
solution is applied to the surface of a precleaned component. The liquid is
pulled into surface breaking defects by capillary action. Excess penetrant
material is carefully cleaned from the surface.
A
developer is applied to pull the trapped penetrant back to the surface where it
is spread out and forms an indication. The indication is much easier to see
than the actual defects
MAIN
USES OF PENETRANT TESTING
It
is used to locate cracks, porosity and other defects that break the other
surface of a material and have enough volume to trap and hold the penetrant
material.
LPT
is used to inspect large areas very effectively and will work on most nonporous
materials.
Equipment’s
used:
1. Developer
2. Penetrant
3. Cleaner
Procedure:
1. Cleaning
(remove oil and dust )
2. Application
of penetrant (red or violet)
3. Remove
of excesses penetrant (dwell of 10 min ) by thinner
5. Evaluation
of the indication
6. Remove
of residual or developer
7. Application
protective coating
Advantages
of LPT:
1. Large
surface areas or large volumes of parts or materials can be inspected rapidly
and at low cost.
2. Parts
with complex geometry are routinely inspected.
3. Indications
are produced directly on surface of the parts providing a visual image of the
discontinuity.
4. Equipment
investment is minimum.
Disadvantages
of LPT:
1. The defects are only surface breaking defects.
2. Surface preparation is critical as
contaminants can mask defects
3. It requires relatively smooth and nonporous
surface
4. Post cleaning is necessary to remove chemical
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