Penetrating Testing
Content
Penetrating Testing (PT)
General statements for Penetrant testing
Discontinuities have to be open to the surface in principle indepe ndent to material but surface not excessively porous important additional test method to magnetic particle testing which can only be used by ferromagnetic material indication is not coming equal to the real size of defect, it is a temporary bleed out
Cohesion
Each of the particles of a substance (molecule) is attracted by its neighbouring molecules. This attraction force is much lower with liquids than with solid materials, with gases it is very much lower than with liquids . Therefore, a liquid, e.g. takes every given room. in spite of this there is a residual cohesion (attraction force) between the liquid particles. If one is aware of this, a variety of facts can be explained.
Surface tension
wetting ability good surface tension low bad surface tension great additional dependence: Viscosity surface roughness
Viscosity
As viscosity the "toughness" of a liquid is meant.
highly dependent on the temperature thermal limits of the penetration test
Adhesion
Adhesion means a sticking of different substances one to the other.
Capillarity
Description of the process
Description of the process
Pre-cleaning and drying
All impurities such as rust, scale, oil, grease, varnish or contamination covering the surface imperfections are to be removed.
Removal mechanical:Pay attention that surface will not be compacted chemical:no residuals which coul influence the testing media
Penetration procedure
Immersion, spraying, brushing, pouring Important: surface must be sufficiently wetted The penetration time depends on the properties of the penetrant, the testing temperature , the material and the defect type: 5 - 60 minutes testing temperature: 5 °C - 50 OC
Excess penetrant removal
removal of excess penetrant from the surface
avoid washing out processes of the penetrant from the surface discontinuities!
1- with solvent 2- with water and solvent
3- three-step excess penetrant removal for post-emulsifiable penetrants using hydrophilic emulsifiers (emulsifier makes penetrant suitable to be cleaned using water): 3 steps:
coarse removal with H2O application of the emulsifiers (Important: time of emulsifying!) cleaning with H2O again
4- Two-step excess penetrant removal for post-emulsifable penetrants using hydrophilic emulsifiers
2 steps :
• • Immersion in emulsifier (Important: time of emulsifying!) washing off with water
developing
Dry developers Dry developers are to be applied in combination with fluorescent penetrant only! electrostatic spraying, f1uidisers, …
solvent based developers (powder suspendable in a solvent) Water soluble developers 1- developer is slurried in water 2- uniform concentration of the developer is important (stirring and mixingprocesses) 3- application can be carried out by spraying or electrostatically
Drying of the surface
Important: 1- testing temperature max, 50°C 2- no pressurised air
developing time
the developing process starts as soon as the dry powder enters into contact with the residual penetrant. developing time between 10 and 30 minutes (depending on the testing system used and the extend of the defects to be proved!)
inspection
The inspection should be carried out at an illumination strength of 500IIx. Surface reflections as well as other reflections should be avoided . If fluorescent penetrants reused the surface should be tested using a UV-A radiation source and a radiation intensity of 1000 µW/cm2
inspection
The surrounding radiation intensity should not exceed 20 Ix (darkened).Thus, a certa in adaptation time is necessary for the human eye that in the standards is indicated with 5 minutes. During the inspection the surface is sought for indications. This should be done directly after drying of the developer (larger defects) and then after termination of the developing time 8 smaller defects). In individual cases intermediate inspections may be necessary.
Testing devices (testing system)
From: EN 571-1
Outward imperction of an angle V-butt weld
This imperfections predominantly step out by the following procedures and are ascertainable by visual inspection:
Interior imperfection of an single V-butt weld
General statements for Penetrant testing
Discontinuities have to be open to the surface in principle indepe ndent to material but surface not excessively porous important additional test method to magnetic particle testing which can only be used by ferromagnetic material indication is not coming equal to the real size of defect, it is a temporary bleed out
Cohesion
Each of the particles of a substance (molecule) is attracted by its neighbouring molecules. This attraction force is much lower with liquids than with solid materials, with gases it is very much lower than with liquids . Therefore, a liquid, e.g. takes every given room. in spite of this there is a residual cohesion (attraction force) between the liquid particles. If one is aware of this, a variety of facts can be explained.
Surface tension
wetting ability good surface tension low bad surface tension great additional dependence: Viscosity surface roughness
Viscosity
As viscosity the "toughness" of a liquid is meant.
highly dependent on the temperature thermal limits of the penetration test
Adhesion
Adhesion means a sticking of different substances one to the other.
Capillarity
Description of the process
Description of the process
Pre-cleaning and drying
All impurities such as rust, scale, oil, grease, varnish or contamination covering the surface imperfections are to be removed.
Removal mechanical:Pay attention that surface will not be compacted chemical:no residuals which coul influence the testing media
Penetration procedure
Immersion, spraying, brushing, pouring Important: surface must be sufficiently wetted The penetration time depends on the properties of the penetrant, the testing temperature , the material and the defect type: 5 - 60 minutes testing temperature: 5 °C - 50 OC
Excess penetrant removal
removal of excess penetrant from the surface
avoid washing out processes of the penetrant from the surface discontinuities!
1- with solvent 2- with water and solvent
3- three-step excess penetrant removal for post-emulsifiable penetrants using hydrophilic emulsifiers (emulsifier makes penetrant suitable to be cleaned using water): 3 steps:
coarse removal with H2O application of the emulsifiers (Important: time of emulsifying!) cleaning with H2O again
4- Two-step excess penetrant removal for post-emulsifable penetrants using hydrophilic emulsifiers
2 steps :
• • Immersion in emulsifier (Important: time of emulsifying!) washing off with water
developing
Dry developers Dry developers are to be applied in combination with fluorescent penetrant only! electrostatic spraying, f1uidisers, …
solvent based developers (powder suspendable in a solvent) Water soluble developers 1- developer is slurried in water 2- uniform concentration of the developer is important (stirring and mixingprocesses) 3- application can be carried out by spraying or electrostatically
Drying of the surface
Important: 1- testing temperature max, 50°C 2- no pressurised air
developing time
the developing process starts as soon as the dry powder enters into contact with the residual penetrant. developing time between 10 and 30 minutes (depending on the testing system used and the extend of the defects to be proved!)
inspection
The inspection should be carried out at an illumination strength of 500IIx. Surface reflections as well as other reflections should be avoided . If fluorescent penetrants reused the surface should be tested using a UV-A radiation source and a radiation intensity of 1000 µW/cm2
inspection
The surrounding radiation intensity should not exceed 20 Ix (darkened).Thus, a certa in adaptation time is necessary for the human eye that in the standards is indicated with 5 minutes. During the inspection the surface is sought for indications. This should be done directly after drying of the developer (larger defects) and then after termination of the developing time 8 smaller defects). In individual cases intermediate inspections may be necessary.
Testing devices (testing system)
From: EN 571-1
Outward imperction of an angle V-butt weld
This imperfections predominantly step out by the following procedures and are ascertainable by visual inspection:
Interior imperfection of an single V-butt weld
