Asme V - LP (chap 14 /(III C) Flashcards
What is purpose of LP?
To detect discontinuities which are open to the surface of non porous metals and other metals.
What kind of discontinuities can be detected?
Cracks, seams, laps, cold shuts, lamination , porosity.
What is cold shut?
Cold shut – Cold shut occurs normally during the casting of parts because of imperfect fusion between two streams of liquid metal which converged together. It can be on the surface or subsurface. It can be attributed to sluggish liquid metal, surging or interruption in pouring, or any factor which prevents the fusion of two meeting streams.
What is seams?
Seams are elongated surface discontinuities which occur in materials during rolling or drawing operations. These result due to under-filled areas which are closed shut during rolling passes. The under-filled areas can result because of blowholes or cracks in the material.
What is laps?
Laps are elongated surface discontinuities which occur during rolling or forging operations due to the presence of some excessive material (fin) that is folded over.
What is lamination?
Laminations are thin flat subsurface separations which are parallel to the surface of the material. These can result from inherent discontinuities such as pipe, inclusions, and porosity etc. which are flattened during the rolling process.
What is prosity?
Porosity is small cavities or bores which are found on the surface of the weld or slightly below surface.
LP testing shall be carried out in conformance with what?
ASTM SE-165
What needs to be included in the written procedure?
- Essential variable of LP testing
- Identification of any changes in type of family group of penetrant materials including developers, emulsifiers, etc
- surface preparation
- Method of applying penetrant
- Method of removing excess surface penetrant
- Hydrophilic or lipophilic emulsifier concentration and dwell time in dips tanks and agitation time for hydrophilic emulsifiers
- Hydrophilic emulsifier concentration in spray application
- Method of applying developer
- Min/ Max time period between steps and drying aids
- decrease in penetrant dwell time
- increase in developer dwell time
- min light intensity
- Surface temp outside
- Performance demo when required.
How to prevent contaminants?
surface must be thoroughly dry after cleaning since nay liquid residue inside defects will hinder the entrance of penetrant. Drying can be done with ovens, infrared lamp, forced hot air, or ambient temp
need the surface of the weld prepared by grinding, machining, or other methods to avoid irregularities of the weld masking indication.
nickel/austenitic/duplex/titanium - shall obtain certification of contaminant content for all liquids penetrant material used
Exam and techniques?
- clean the surface with cleaner
- remove all cleaner, let dry
- apply penetrant
- wipe excess amount, and wait
- apply developer
- wait (between 10-60 min)
what are the 3 penetrant processes
- water washable
- post-emulsifying
- solvent removable
Color contrast penetrants
- developers forms a reasonably uniform white coating, surface discontinuities are indicate by bleed out of the penetrant, indication with alight pink color may indicate excessive cleaning.
- cleaning is important
- min light intensity of 100 fc is required on the surface to be examined
Fluorescent penetrants
- same as color except performed with UV light called black light
- performed in a darkened area.
- examiners shall in a darkened area for atleast 5 min prior to performing examination to enable theirs eyes to adapt
- black light shall achieve a min of 1000 uW/cm2 of the surface of the part being examples
documentation
all indication (non reject able or reject able)shall be recorded.
