LPT..pptx

Dye Penetrant Testing

1. DYE PENETRANT TESTING (1850) BY MANISH SHARMA

2. LIQUID PENETRANT INSPECTION (LPI /LPE/LPT) DYE PENETRANT TESTING (DPT/ DPE/DPI ) PENETRANT FLAW DETECTION(PFD) PENETRANT TESTING(PT)

3. Introduction : Finding discontinuities open to the surface of the material to work on the principle of capillary action and it is applicable to both magnetic and non magnetic materials. Capillary action forces liquid into narrow openings

4. Capillary Action This is the phenomenon of a liquid rising or climbing when confined to small openings due to surface wetting properties of the liquid.

5. Basic Process of PT 1) Clean & Dry Component 2) Apply Penetrant 3) Remove Excess 4) Apply Developer 5) Visual Inspection

6. Basic Principle : The liquid penetrant is applied on the surface of the component to be tested. The penetrant enters into the discontinuities by capillary action, if the discontinuity is small or narrow, the capillary action assists the penetration, If the discontinuity is large in nature, the penetrant seep through the discontinuity. After sufficient time has passed for the penetrant to enter the surface discontinuity, The excess penetrant on the surface is removed by washing or some other convenient manner.

7. But the penetrant in the discontinuity is allowed to remain, Then developer is applied to the test surface, the blotting action of the developer draws the penetrant from the discontinuity & the penetrant appears on the surface of the specimen as an indication.

8. Requirements: Job ( Smooth, Non porous metal) Approved Procedure D.P. materials • Cleaner • Penetrant • developer • Lint free cloths/clean cloths Light arrangement • Ordinary light (sunLight or 100 Watt Bulb etc.) • Black light ( U .V .Light ) Reference Block • Aluminium Crack Block • Nickel Chromium panel. 6. Technician( SNT-TC-1A )

9. NOTE: Materials that are commonly inspected using LPI include the following. Metals ( AL, CU, Steel, titanium etc. ) Glass Many ceramic materials Rubber plastic

10. Basic Theory of Penetration: Penetration (ability to penetrate) ↓ depends upon Wettability (ability to wet) ↓ depends upon Contact Angle (the angle between solid material and liquid or gas.

11. If Contact angle is less than 90⁰ then wettability is very good. If contact angle is 90⁰ then wettability is fair (average good) If Contact angle > 90⁰ then poor wettability.

12. Contact angles depends upon. 1. Surface Tension(T= F/ L ) The molecules in a liquid are attracted to each other. 2. Viscosity (resistance to flow the liquid) & it is affected by temp & pressure.

13. Steps in DPT 1. Precleaning (surface preparation) Liquid penetrant test is based on ability of the penetrant to enter into the surface discontinuity/ Discontinuities The specimen to be tested must be clean and free from foreign matters that may covers or block the discontinuity.

14. surface preparation

15. Types of Contaminant : Paint on the specimen . Oils, greases & other chemical impurities. Dirt or dust that gets settled on the surface of the job. Polising component & scales from heat treatment or welding. Welding flux & weld spatters.

16. Cleaning Methods: Mechanical Method: Mechanical cleaning means removal of contaminants from the surface by various mechanical operations. (A) Abrasive tumbling : Removing light scales, welding flux, rust etc. It should not be used on soft materials such as Al, Mg,etc . (B) Wire Brushing : Removing light deposits of scales, flux & rust.

17. (C) High pressure water & steam : we use water and detergent to removes types of contaminants Such as cutting oil, grease, chips, polishing components. (D) Ultrasonic cleaning: we dissolved detergent in water to removes adherent shop soils in large quantities from small parts by dipping the part in a ultrasonic tank. The frequency of ultrasonic vibration is 30 to 40 KHz is generally used but some times higher frequency may be used.

18. CHEMICAL METHOD: Alkaline Cleaning: (PH > 7) Remove typical machine shop soils such as cutting oil, polishing components, grease & wax, metal chips, carbon deposits used on large specimen where hand methods are too laborious. Alkaline solution = Caustic Soda or lime. Sodium & potassium Hydroxide ( NaOH , KOH) etc. Cleaning method Immersion at temp (50- 95⁰) & then water rinse or spraying usually to remove residue.

19. 2. Acid Cleaning: Typically known as etching used acid to remove scales & smeared metal pieces due to machining operation. A concentrated solution for removing heavy scales, mild solutions for light scales.

20. 3.Solvent Cleaning Methods: Solvent wiping : It is the most common method for pre & post cleaning & must be performed in a well ventilated area due to toxicity of the vapors.

21. 2. Penetrants: Almost any Liquid could be penetrant but a modern penetrant must have the following properties.

22. 1.It should be able to easily penetrate to very fine openings. 2. Be able to remain on the openings. 3. Not evaporate or dry up too rapidly. 4. Clean easily off the surface on which it has been applied. 5. uniform flow property. 6. In a short time, come back out to very fine openings. 7. Dye should be high contrast colour like Red/Pink.

23. 8. Good wettability. 9. Can be used on any material which has a non absorbent surface. 10. Penetrant made of dye + solvent (dye for contrast & solvent for carrier) 11. Not be harmful to the inspector or the material being tested.

24. Types of penetrants : It depends upon Quality, cost, service condition & sensitivity required. penetrants are classified which are as. Solvent removal visible colour contrast. Solvent removal fluorescent. Water washable visible colour contrast. Water washable fluorescent. Post emulsiable colour contrast. Post emulsiable fluorescent.

25. Post Emulsification Penetrant system: Post emulsification penetrants have high sensitivity it can detect miner defects , than that of water washable & solvents removable. such penetrants have an oil base & require an additional processing step. An emulsifier is applied after the penetrant had sufficient time to be absorbed by the defects.

26. They are of two types: 1. Hydrophilic (water based) 2. Lipophilic Emulsifier (oil based) Emulsification dwell time is from a few seconds to several minutes typically 15 sec to 4 min. The Emulsifier can be applied by dipping or spraying but not by brushing . The bristles of the brush may enter the discontinuity.

27. Advantage of post Emulsification Penetrant: High sensitivity to very fine discontinuities. Penetrant easily washed with water after emulsification.

28. Disadvantages of post Emulsifiable penetrant: It is two step process & requires additional time in making the penetrant water washable. Separate emulsifiers are required , which raises the cost of inspection. Not good on rough surface. Penetrant removal is difficult in threaded parts, holes.

29. Application of Penetrant : By Brush By Spray By Pouring By Dipping .

30. Physical properties of a good developer: Have uniform well dispersed micro particals. Have Light Scattering efficiency (i.e. high back ground contrast (white) Low contact angle between developer & solid surface. Non Toxic. It must be easily removable after inspection. Developers: The primary function of the developer is to absorb or draw the penetrant (blotting action ) from discontinuity .

31. There are five types of developers: Dry Wet (Aqueous –water Soluble) Wet(Aqueous-Water Suspended) Solvent ( Non aqueous wet ) Film Type

32. a. Dry Developers: Dry developer shall be applied only to a dry surface by a soft brush or hand powder bulb, powder gun , etc .

33. b. Wet Developer: Prior to applying suspension type wet developer to the surface, the developer must be thoroughly agitate to ensure adequate dispersion of suspended particles. Wet developers are applied by dipping, brushing, spraying on the part. The part is then dried in a hot air circulating oven, but surface temp of the part (job) shall not exceed 52⁰c.

34. c. Non Aqueous Developers: (Solvent) Suspended Non aqueous developer shall be applied only to a dry surface. It shall be applied by spraying to a thoroughly dried & cooled part.

35. d. Liquid Film Developers: The film type developer as the name implies to form a plastic film over a surface as it dries. It is normally applied by spraying as with the non-aqueous wet type developer. As the film dries it exposed penetrant indications set (fixed) in the pattern. The film provide a permanent record of the discontinuity pattern.

36. Application of Developer: By Brush By Spray By Pouring By Dipping Same as application of penetrant.

37. Development Time : The length of time the developer is allowed to remain on the part prior to examination, should not be less than 10 minutes. Permitted developing time are 2 hrs for aqueous developers & 1 hrs for non Aqueous developers. “ Generally developing time is double to dwell time of penetrant”.

38. Dwell time or Penetration time: The period of time during which the penetrant is permitted to remain on the specimen is a vital part of the test. This time is often referred to as a penetration time, or dwell time. Normally this time is dependent on the nature of discontinuities, surface finish, material type & temp ,Penetrant type.

39. Material Form Type of Discontinuity Penetration dwell time Developer dwell time Brass, Al, Mg, Steel Bronze Ti & High Temperature Alloys. Casting & Welds Wrought materials extrusions forgings & plates Cold shuts Porosity, LOF, Cracks Laps, Cracks (all forms) 5 10 10 10 Plastic All Forms Cracks 5 10 Glass All Forms Cracks 5 10 Ceramics All Forms Crack 5 10 Carbide Tipped tools Porosity Cracks 5 10

40. The above table is valid for temperature range= 10⁰ - 52⁰C .For temperature from 5⁰c up to 10⁰c minimum penetrant dwell time shall be 2 times the value listed.

41. Excess Penetrant Removal: The excess penetrant removal technique depends upon the type of penetrant used e.g . 1. Water washable 2. Post Emulsifiable 3. Solvent Removable

42. Water washable penetrants : After the required penetration time, the excess penetrant is usually removed by coarse spray of water. It can be washed off manually or by the use of automatic or semi automatic water spray equipments or by immersion. This method is the easiest to employ & most cost effective when inspecting large areas.

43. Used (Parameters) The temp of the water should be relatively constant & should be maintained within the range of (10⁰C – 38⁰C) Spray rinse water pressure should not greater than 50 PSI(280 Kpa ) Rinse time should not exceed 120 sec unless other wise specified by governing procedure. Using a coarse spray at a minimum distance of 12 inches.

44. Water washable: A coarse water spray removes loose penetrant by scrubbing action :

45. 1. Water washable: (STEPS) Precleaning by rinsing 2. Dry by blower (hot circulating air) 3. Application of penetrant 4. Dwell time Removal of excess penetrant by water wash (shall be applied by coarse bubble flow) 6. Drying

46. 7. Application of developer 8. Developing time 9. Interpretation 10. Post Cleaning 11. Report

47. 2.(A) Post Emulsifiable Penetrants ( Lipophilic ): After the required penetrant dwell time, the part must be emulsified by immersing with emulsifier, effective post rinsing is done either by manual automatic or semi automatic spray equipments.

48. 2(B). Post Emulsifiable Penetrants: (Hydrophilic) After the required penetrant dwell time & prior to emulsification the part shall be pre rinsed with water spray using the same process as for water washable penetrants. Pre rinsing time shall not exceed 1 min after pre rinsing the excess surface penetrant shall be emulsified by immersing in or spraying with hydrophilic emulsifier. After emulsification the mixture shall be removed by immersing in or rinsing with water.

49. 2 . Post Emulsifiable Preclean Penetrant application Dwell time Emulsification water wash rinse dry part Apply Aqueous developer(water) Apply Developer Dry Dwell time Dwell time Inspection Inspection Post Clean Post clean

50. 3. Solvent Removable : Penetrants are removed by wiping with a cloth, moistured with solvent. They are supplied in aerosol cans for portability & are primary used for spot checks (small area).

51. 3.Solvent Removal Penetrants Precleaning Application of penetrant Dwell time Excess penetrant removal Application of Developer Developer Dwell time Interpretation Post Cleaning Reporting

52. 1.Solvent Removable 1. Visible 2. Fluorescent 1- Interpretation shall be carried out in an ordinary light .At inspected surface light intensity ( minimum 1000 lux ) 1- Interpretation Shall be carried out at a dark place under UV light (black light) Intensity = 1 000 micro watt/cm² at a distance from 12” and dark room intensity should be less than 20 lux . 2- Colour indication Yellowish green. Min warming time of U.V lamp should be (5-10) min prior to inspection. But in LED Ultraviolet Lamp Warming is not required. 2-Colour indication Red/ Pink “ We should have pocket magnifier range =3 -10 (x)

53. NOTE: Distance of spray to specimen = 8”-10” Angle of spray to specimen = 30⁰ -40⁰ To normal

54. Fluorescent light ( u.v . light)

55. Summary of penetrant processes.

56. D.P. Set up Portable D.P. Kit Permanent Online setup Kit Contains 1. Cleaner For Mass Production 2. Developer 3. Penetrant 4. Lint free cloth 5. Light Arrangement Cl , S, Free D.P Material is used.

57. Name of Manufacturers of developer & Penetrant: Magna Flux P. Met Check met Pradeep Metal Flaw Check Reference Blocks : The Blocks made of aluminium steel, nickel, glass or ceramics some of them are used for checking the sensitivity of test system by comparison.

58. 1. Aluminium Cracked Block. (ASTMB 209 Type 2024) Standard temp = 10⁰- 52⁰ (according to ASME SEC V article 6 appendix III To Compare DP material & performance of Penetrants. The Blocks are heated & quenched to produce an overall circular cracks pattern.

59. Aluminium Cracked Block. (ASTMB 209 Type 2024)

60. 2. Nickel Chromium Panel The Ni– Cr test panel are ideal penetrant sensitivity comparators . The comparators are available with 10, 20, 30, 50 (microns).

61. Discontinuity can be detected by DPT 1. (Rolled Product) PLATE : Cracks Porosity (pinhole) Edge lamination Crack: Sharp linear with zigzag (~) Porosity: Round, with defined boundaries Edge Lamination: Sharp linear straight (-) 2. Welding : 1- crack & Porosity appear same as plate Undercut – Irregular width 3. Casting : Hot tear, blow holes , porosity, cold shuts shrinkage. 4. Forging : Crack, Lap, external bursts.

62. Recording of Indications: Photography (Video recorded by CCTV camera. Sketch / design drawing. Transparent adhesive tape (Replica transfer coating (RTC).

63. INTERPRETATION Evaluation of indication Relevant Indication from actual discontinuities By capillary action Any indication whose measure dimension exceed 1/16” (1.59mm) then it is called relevant. (1)-Linear – if L > 3w (2)-Rounded – if L ≤ 3w Non Relevant Any indication less than 1.59 mm due to capillary action False indication due to improper handling the method or by design itself without capillary action. Beyond acceptable limit of discontinuity is called defect. All Discontinuity is not defect but all defect is discontinuity.

64. indication Fluorescent indication Color contrast indication

65. indication Color contrast Indication : Crack indication. Bleed out shows a gross defect.

66. Fluorescent indication Numerous crack Indications

67. Post Cleaning : The final step in the penetrant inspection process is to throughly clean the part that has been tested.

68. Advantages of D.P.T The process is relatively simple as no electric system is required. Low capital cost. Establishment of procedure & standard is less difficult. Difficult shapes & sizes can be inspected. Suitable for both metal & non metals Aerosol spray cans make equipment portable. Initial equipment investment is low. D.P.T provides a proof that a defect has comes to the surface.

69. Limitations It can detect flaws which are open to the surface / surface breaking discontinuity. Require smooth non porous material. Contamination can mask defects when cleaning the specimen. Chemical handling precaution necessary (toxicity, fire) Post cleaning is necessary to remove chemical to avoid corrossion