1. ME367 NON-DESTRUCTIVE TESTING MODULE-2 Sukesh O P, AP-ME, JECC 10/16/2018 SUKESH O P/ APME/JECC 1

2. ME357 Non-Destructive Testing 10/16/2018 SUKESH O P/ APME/JECC 2 Introduction to NDT- Visual Inspection- Liquid Penetrant Inspection- Magnetic Particle Inspection- Ultrasonic Testing- Radiography Testing- Eddy Current Testing.

3. MODULE-2 10/16/2018 SUKESH O P/ APME/JECC 3  Liquid Penetrant Inspection: principles, properties required for a good penetrants and developers - Types of penetrants and developers. and advantages and limitations of various methods of LPI - LPI technique/ test procedure- interpretation and evaluation of penetrant test indications, false indication and safety precaution required in LPI, applications, advantages and limitations.

4. Liquid Penetrant Inspection (LPI) 10/16/2018 SUKESH O P/ APME/JECC 4  Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI) or penetrant testing (PT), is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics).  LPI is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.

5. Principle 10/16/2018 SUKESH O P/ APME/JECC 5  DPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface- breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing.  After adequate penetration time has been allowed, the excess penetrant is removed and a developer is applied. The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible to the inspector.  Inspection is performed under ultraviolet or white light, depending on the type of dye used - flurescent or nonfluorescent (visible).

6. Inspection steps 10/16/2018 SUKESH O P/ APME/JECC 6 1. Pre-cleaning 2. Application of penetrant 3. Removals of excess penetrant 4. Application of Developer 5. Inspection 6. Post cleaning

7. Processing steps of LPI 10/16/2018 SUKESH O P/ APME/JECC 7

8. Processing steps of LPI Processing steps of LPI 1. Pre-cleaning 10/16/2018 SUKESH O P/ APME/JECC 8  The test surface is cleaned to remove any dirt, paint, oil, grease or any loose scale that could either keep penetrant out of a defect, or cause irrelevant or false indications.  Cleaning methods may include solvents, alkaline cleaning steps, vapor degreasing, or media blasting. The end goal of this step is a clean surface where any defects present are open to the surface, dry, and free of contamination.

9. Cleaning methods  Mechanical methods:  Brushing  Blasting  Chemical methods:  Hot solvent degreasing  Vapor degreasing  Cold solvent degreasing  Alkaline degreasing  Acid pickling  Steam cleaning  Paint strippers

10. Physical Cleaning Grinding Abrasive Blasting Wire brushing Defect Peened or Closed

11. Light Acid Etching Light Acid applied Thin layer of the surface dissolved

12. Light Acid Etching After Acid Etching The defect opened again to the surface

13. Chemical Methods Hot Solvent Degreasing Heating Element Solvent Components

14. Heating Element Solvent Components Condensor Drip Tray vapour The most effective method for degreasing Vapour Degreasing

15. Steam Cleaning  For large objects

16. Processing steps of LPI Processing steps of LPI 2. Application of penetrant 10/16/2018 SUKESH O P/ APME/JECC 16  After cleaning the surface from any type of foreign contaminants, penetrants are applied may be by immersing the job into penetrant dilution or by brushing or by spraying.

17. Processing steps of LPI Processing steps of LPI 2. Application of penetrant 10/16/2018 SUKESH O P/ APME/JECC 17  DWELL:  DWELL: It is a certain period of time for which penetrant is left to be in contact with surface of job till it dries. This dwell period varies according to type of penetrant used, material on which penetrant is applied, type of defect for which it is applied, etc.  Generally minimum dwell period varies up to 60 minutes.  The specimens size, composition, temperature, nature of discontinuity, all affect the penetration time, which is also called as dwell time.

18. Processing steps of LPI Processing steps of LPI 3. Removals of excess penetrant 10/16/2018 SUKESH O P/ APME/JECC 18  This is a very complicated step, where precise level of care is required to remove the excess penetrant from the surface while leaving penetrants for defects also.  It may be done by direct rinsing with water, by cleaning with a solvent, or first treating it with emulsifier, then rinsing with water.

19. Processing steps of LPI Processing steps of LPI 4. Application of Developer 10/16/2018 SUKESH O P/ APME/JECC 19  For clear visualization of defect, a thin layer of developer is applied on the surface of job, which draws out the penetrant trapped in flaws back to the upper surface.  Developer may be used in dry (dusting)or wet form(dipping and brushing).  Several developer types are available, including: non- aqueous wet developer (NAWD), dry powder, water- suspendable, and water-soluble. Choice of developer is governed by penetrant compatibility and by inspection conditions.

20. Processing steps of LPI Processing steps of LPI 5. Inspection 10/16/2018 SUKESH O P/ APME/JECC 20  Inspection of the test surface should take place after 10-to-30 minute development time, depends of product kind. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye.  The inspector will use visible light with adequate intensity (100 foot-candles or 1100 lux is typical) for visible dye penetrant. Ultraviolet (UV-A) radiation of adequate intensity (1,000 micro-watts per centimeter squared is common), along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations. foot-candleslux

21. RESULTS -LPI 10/16/2018 SUKESH O P/ APME/JECC 21

22. Processing steps of LPI Processing steps of LPI 6. Post Cleaning 10/16/2018 SUKESH O P/ APME/JECC 22  The test surface is often cleaned after inspection and recording of defects, especially if post- inspection coating processes are scheduled.

23. Characteristics/Properties required for a good penetrants 10/16/2018 SUKESH O P/ APME/JECC 23 Chemical stability & uniform physical consistency High degree of wettability Quick & complete penetrability Low viscosity Sufficient brightness & permanence of colour Chemical inertness Low toxicity Slow drying Ease of removal Low cost

24. Penetrant Properties  Wetting ability  Specific gravity  Volatility  Chemical activity  Solubility  Solvent ability  Health hazard  Tolerance to contaminants  Flammability / flash point  Electrical conductivity  Availability and cost

25.  Wetting ability:  Affect penetrability and bleed-back characteristics  Contact angle and surface tension of penetrant control wetting ability  Specific gravity:  Ratio of density of penetrant with density of distilled water at 40  C  Not a problem with oil base penetrant  Penetrant used in tank system must have specific gravity less than 1  to ensure water will not float on top of penetrant  prevent penetrant from covering the test object Penetrant Properties

26.  Flash point:  Temperature at which enough vapor is given off to form combustible mixture  Typical min 93  C  Should not be flammable  Volatility:  Characterize by vapor pressure or boiling point  Good penetrant usually evaporate too quickly  Low volatility is desirable  so the penetrant dry from the surface, leave stained and from any discontinuity, leave precipitated dye

27. Penetrant Properties  Chemically inert:  Must be inert, non-corrosive as possible  chemically compatible with the material being tested  Penetrant is contaminant (contain sulphur, sodium, halogen)  potential reactions must be considered  To avoid possibility of embrittlement or cracking over years  Viscosity:  Affect thickness of penetration due to molecular/internal friction  Low viscosity penetrant  Solubility:  Penetrant contain dye in liquid solution  Must hold sufficient dye at ambient or high temperature  Must not come out from solution if temperature drop

28. Penetrant Properties  Solvent ability:  Solvent must be able to remove surplus penetrant from test specimen  To ensure clean, clear background  Must not dissolve the penetrant in defect  Tolerance to contaminants:  Penetrant will be contaminated after a period of time, even if a great care is taken  Must be periodically check to ensure all is well, no residue left

29. Penetrant Properties  Health hazard:  Must comply with or exceed the most stringent HSE requirements Toxicity, odour, skin contact  To prevent allergies or contaminants  Availability and cost:  Dye materials are easily obtained  Low cost

30. Penetrant Properties  Electrical conductivity:  Electrostatic spraying becomes popular  uniform coverage with complicated shapes  Reduces over spraying  Requires less penetrant over all  Spray gun applies –ve charge to penetrant  Test object ground potential  Electrostatic attraction cause penetrant be strongly attracted to the part  low viscosity and easily attracted to the part  Must readily accept and hold the electrical charge

31. Developer properties  Good developer:  Material must be absorptive to perform blotting action  Must have fine texture  Must mask out background contours and colors  Must be easily and evenly applicable  Must form light and even coat  Must be no fluorescing of developer when fluorescent penetrant is used  Penetrant bleeding must easily wet the material  Must be high color contrast, white is the best  Must be readily removable after test  Must be in-toxic and non-irritant

32. Type of penetrants 10/16/2018 SUKESH O P/ APME/JECC 32  For different materials inspection penetrant manufactures have developed different penetrant for proper inspection.  For small defect and smooth surface penetrants required are some dirrerent kind. Similarly for large defects.

33. Type of penetrants/developers Penetrant Type I Fluorescent II Visible Method A Water Washable B Postemulsifiable - Lipophilic C Solvent Removable D Postemulsifiable - Hydrophilic Developer Form Dry Powder Wet, Water Soluble Wet, Water Suspendable Wet, Non-Aqueous

34. Type of penetrants 10/16/2018 SUKESH O P/ APME/JECC 34  in which a fluorescent dye is applied to the surface of a non-porous material in order to detect defects that may compromise the integrity or quality of the part in question. Noted for its low cost and simple process, FPI is used widely in a variety of industries.

35. Fluorescent penetrants V/s Visible penetrants 10/16/2018 SUKESH O P/ APME/JECC 35 Fluorescent penetrantsVisible penetrants It consist of dyes that flouresce, when ultraviolet radiations are exposed on them. It consists of red dye, which produces a fine range of contrast against the white developer background. They are more sensitive.They are less sensitive. It requires darkened area and ultraviolet radiations for inspection. It doesn't require any dark area and ultraviolet radiations for inspection. They are more vulnerable to contaminationThey are less vulnerable to contamination

36. Why is Visible Penetrant Red and Fluorescent Penetrant Green? Visible penetrant is usually red because red stands out and provides a high level of contrast against a light background Fluorescent penetrant is green because the eye is most sensitive to the color green due to the number and arrangement of the cones (the color receptors) in the eye.

37. Penetrant methods 10/16/2018 SUKESH O P/ APME/JECC 37  Method A- Water washable  Method B- Post-emulsifiable, Lipophilic(oil base)  Method C- Solvent removable  Method D- post-emulsifiable, Hydrophilic(water base)

38. Penetrant methods Penetrant methods Method A- Water washable 10/16/2018 SUKESH O P/ APME/JECC 38  Water washable penetrants are slso referred to as self-emulsifying penetrants. This penetrants consists of an emulsifying agent namely detergents, which helps it get removed from the part by rinsing with water only.  ADV:-  Sensitivity is high  Cost involved is less  Large surface discontinuities can be visualized  Removal of penetrant is very easy

39. Penetrant methods Penetrant methods Method A- Water washable 10/16/2018 SUKESH O P/ APME/JECC 39 DIS ADV:-  Dark environment is required for evaluation  Insensitive to shallow discontinuities  Method is not portable  Quality of penetrant is degraded by contamination.

40. Penetrant methods Penetrant methods Method B&D- Post-emulsifiable, Lipophilic & Hydrophilic 10/16/2018 SUKESH O P/ APME/JECC 40  Post emulsifiable penetrants come in two categories: Lipophilic and hydrophilic. Where lipophilic are oil soluble, it interacts with oil-based emulsifier to make removal possible and hydrophilic are water soluble. It interacts with detergent based emulsifier to remove the excess penetrant with water wash only. ADV:- Sensitivity is high for small discontinuities Sensitive to shallow discontinuities Not affected by acids.

41. Penetrant methods Penetrant methods Method B&D- Post-emulsifiable, Lipophilic & Hydrophilic 10/16/2018 SUKESH O P/ APME/JECC 41 Limitation :- Method is not portable It requires an emulsifier Takes more time In effective for complex and rough surfaces.

42. Penetrant methods Penetrant methods Method C Solvent removable 10/16/2018 SUKESH O P/ APME/JECC 42 Solvent removable penetrants uses solvents for penetrant removal from surface. ADV:- Sensitive to discontinuities of spot size. When water removal fails, it provides feasible technique. LIMITATION:- Limited to small areas Black light and dark environment is required. Back ground indications are also generated, which affects the contrast ratio Sensitivity reduces if excess remover is used.

43. Developer types The primary methods for the following main developer types will be covered in the following slides. – Dry – Wet (water- suspended and water- soluble) – Nonaqueous Wet

44. Developer types Developer types Dry Powder Developer Prior to applying a dry powder developer, the component must be thoroughly dried. Drying is usually accomplished in a hot air circulating oven. The developer is then applied by immersing the part in the powder or by dusting of the part with the powder. The part can also be placed in a developer dust cloud chamber.

45. Developer types Developer types Wet Developer (water- suspended and water- soluble) Wet developers are applied by immersing or spraying the part while it is still wet from the penetrant removal process. The part is completely coated and the excess liquid allowed to drain to prevent pooling The part is then dried in a hot air circulating oven.

46. Developer types Developer types Nonaqueous Developer (Solvent-Suspended) Nonaqueous developer is applied by a aerosol spray to a thoroughly dried and cooled part. A thin even coating should be applied. The coating should be white but still slightly transparent when performing a visible dye penetrant inspection, and even thinner when performing a fluorescent penetrant inspection.

47. INTERPRETATION AND EVALUATION OF PENETRANT TEST INDICATIONS 10/16/2018 SUKESH O P/ APME/JECC 47  LPI indications depend on the type of penetrant used. If fluorescent penetrant is used, defect show- up as glowing yellow-green dots or lines against a dark background. In the case of die penetrant ; defects are indicated as red dots or lines against a white background.

48. INTERPRETATION AND EVALUATION OF PENETRANT TEST INDICATIONS 10/16/2018 SUKESH O P/ APME/JECC 48  The interpretation of the characteristic patterns indicating the types of flaws is of great significance. For example, a crack of a small opening is indicated by a line of penetrant.dots of penetrant indicate pits or porosities on the surface of object under inspection. Such dots appear over an area or isolated spots and generally do not from a line pattern. A series of dots forming a line pattern indicates a tight track, cold shut or partially welded lap. Fatigue cracks also generally appear in the form of a series of very fine dots.  May obtain a rough estimate of the surface opening by measuring the width of the indication( the amount of spreading of the penetrant on the developer). There doesn’t exist a definite relationship between the surface opening and spreading of the penetrant.

49. SAFETY PRECAUTIONS 10/16/2018 SUKESH O P/ APME/JECC 49  Proper cleaning is necessary to assure that surface contaminants have been removed and any defects present are clean and dry. Some cleaning methods have been shown to be detrimental to test sensitivity, so acid etching to remove metal smearing and re-open the defect may be necessary. Penetrant dyes stain cloth, skin and other porous surfaces brought into contact.  One should verify compatibility on the test material, especially when considering the testing of plastic components.

50. SAFETY PRECAUTIONS Health and Safety Precautions 10/16/2018 SUKESH O P/ APME/JECC 50  Chemical Safety : Before working with a chemical of any kind, it is highly recommended that the material safety data sheets (MSDS) be reviewed so that proper chemical safety and hygiene practices can be followed.  Some of the penetrant materials are flammable and, therefore, should be used and stored in small quantities. They should only be used in a well ventilated area and ignition sources avoided. Gloves and other protective clothing should be worn to limit contact with the chemicals.  Eye protection should always be worn to prevent contact of the chemicals with the eyes. Gloves and other protective clothing should be worn to limit contact with the chemicals.

51. SAFETY PRECAUTIONS Health and Safety Precautions 10/16/2018 SUKESH O P/ APME/JECC 51  Ultraviolet Light Safety Ultraviolet (UV) light has wavelengths ranging from 180 to 400 nanometers. These wavelengths place UV light in the invisible part of the electromagnetic spectrum between visible light and X-rays.  Skin and eye damage occurs at wavelengths around 320 nm and shorter which is well below the 365 nm wavelength, where penetrants are designed to fluoresce. Therefore, UV lamps sold for use in penetrant testing are almost always filtered to remove the harmful UV wavelengths. The lamps produce radiation at the harmful wavelengths so it is essential that they be used with the proper filter in place and in good condition.

52. Applications  Turbine rotor discs & blades  Aircraft wheels, castings, forged components, welded assemblies  Automotive parts – pistons, cylinders, etc.  Bogie frames of railway locomotives & rolling stock  Electrical ceramic parts – spark plug insulators, glass-to-metal seals, etc.  Moulded plastic parts

53. Advantages & Limitations of Liquid Penetrant Method ADVANTAGES  Simple & inexpensive  Versatile & portable  Applicable to ferrous, non- ferrous, non-magnetic & complex shaped materials which are non-porous & of any dimension  Detects cracks, seams, lack of bonding, etc. LIMITATIONS  Detect surface flaws  Non-porous surface for material  Surface cleaning before & after inspection  Deformed surfaces & surface coatings prevent detection

54. 10/16/2018 SUKESH O P/ APME/JECC 54 In general, penetrant testing is more effective at finding:  Small round defects than small linear defects.  Deeper flaws than shallow flaws.  Flaws with a narrow opening at the surface than wide open flaws.  Flaws on smooth surfaces than on rough surfaces.  Flaws with rough fracture surfaces than smooth fracture surfaces.  Flaws under tensile or no loading than flaws under compression loading.

55. Module-2(Summary) Penetrant testing (PT) is one of the most widely used nondestructive testing methods. Its popularity can be attributed to two main factors, which are its relative ease of use and its flexibility. However, PT involves a number of processing steps that must be closely control to achieve optimal sensitivity.

56. Glossary of Terms Capillary Action - the tendency of certain liquids to travel or climb when exposed to small openings. Contrast - the relative amount of light emitted or reflected between and indication and its background. Defect - a discontinuity that effects the usefulness of a part or specimen. Developer - a finely divided material applied over the surface of a part to help promote reverse capillary action and thus bring out a penetrant indication.

57. Glossary of Terms Discontinuity - any interruption in the normal physical structure of a part or weld. It may or may not affect the usefulness of a part. Dwell Time - the period of time that a penetrant or developer must remain in contact with the surface of a part under test. Emulsification Time - the time allowed for the emulsifier to render the penetrant water washable and thus allow the part to be washed. Emulsifier - a material applied over a film of penetrant that renders it water washable.

58. Glossary of Terms Evaluation - the process of deciding as to the severity of the condition after an indication has been interpreted. False Indication - an indication caused by improper processing; not caused by a relevant or non-relevant condition. Flash Time - the time required for the solvent to evaporate from the surface of a part when used to preclean or remove excess penetrant. Fluorescent Dye - a dye which becomes fluorescent (gives off light) when exposed to short wave radiation such as ultraviolet light.

59. Glossary of Terms Indication - the visible evidence or penetrant bleed-out on the surface of the specimen Interpretation - the process of evaluating an indication in an attempt to determine the cause and nature of the discontinuity. Non-Aqueous Developer - a developer in which developing powder is applied as a suspension in a quick drying solvent Penetrant - a liquid used in fluorescent or visible dye penetrant inspection to penetrate into the surface openings of parts inspected via these methods

60. Glossary of Terms Relevant Indication - an indication that has been determined not to be false or non-relevant - and actual discontinuity Seeability - the characteristic of an indication that enables it to be seen against the adverse conditions of background, outside light, etc. Sensitivity - the ability of a penetrant to detect surface openings. Higher sensitivity indicates smaller discontinuities can be detected Ultraviolet Light (or Black Light) - light energy just below the visible range of violet light (356 nanometers).

61. Glossary of Terms Viscosity - the resistance of a fluid to the motion of its particles Washability - the property of a penetrant which permits it to be cleaned from the surface of a part by washing with water

62. TASK -2 (MODULE-2) ME367 NDT TASK -2 (MODULE-2) 10/16/2018 SUKESH O P/ APME/JECC 62  Explain Quality and process control of LPI.  Explain about the various test stations of LPI. Submit on or before : 29/8/17 (in class note)

63. ME367 NDT 10/16/2018 SUKESH O P/ APME/JECC 63 END OF MODULE -2

64. 10/16/2018 64 SUKESH O P/ APME/JECC