DT N NDT.pptx non destructive methods on ce

Corrosion engineering module non destructive methods

1. REVIEW OF FABRICATION TECHNOLOGY DT AND NON-NDT METHODS

2. WHAT IS FABRICATION ? Manufacturing process in which an item is made (fabricated) from raw or semi-finished materials instead of being assembled from ready-made components or parts.

3. In Fabrication technology, there are 2 main parts :- DT ( Destructive Technique ) NDT ( Non Destructive Technique)

4. DESTRUCTIVE TESTING In  destructive testing , tests are carried out to the specimen's failure, in order to understand a specimen's structural performance or material behaviour under different loads. These tests are generally much easier to carry out, yield more information, and are easier to interpret than nondestructive testing. Destructive testing is most suitable, and economic, for objects which will be mass-produced, as the cost of destroying a small number of specimens is negligible. It is usually not economical to do destructive testing where only one or very few items are to be produced (for example, in the case of a building).

5. Some types of destructive testing: Stress tests Crash tests Hardness tests Metallographic tests

6. STRESS TESTING :- Stress testing  (sometimes called  torture testing ) is a form of intense or thorough testing used to determine the stability of a given system or entity. It involves testing beyond normal operational capacity, often to a breaking point, in order to observe the results. Reasons can include: To determine breaking points or safe usage limits To confirm intended specifications are being met To determine modes of failure (how exactly a system fails) To test stable operation of a part or system outside standard usage.

7. CRASH TESTING :- The act of crashing under controlled conditions in order to assess its safety for passengers To test (a new product) for safety and reliability by finding out its breaking point under pressure, heat, etc For Eg.: New Car

8. HARDNESS TESTING :- Hardness is the property of a material that enables it to resist plastic deformation, usually by penetration. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting. Hardness  is a measure of how resistant solid matter is, to various kinds of permanent shape change when a force is applied. Common examples of  hard matter  are ceramics, concrete, certain metals, and  super hard materials

9. METALLOGRAPHIC TESTS :- A test to determine the structural composition of a metal at low and high magnification and by x-ray diffraction methods; tests include macroexamination, microexamination, and x-ray diffraction studies. Ceramic  and polymeric materials may also be prepared using metallographic techniques

10. NON DESTRUCTIVE TESTING :- Quality control method that does not damage or destroy the material or product being tested. NDT is examination of an object in any manner which will not damage in future. It is carried out to locate the internal defects of material. Thus NDT give reliability accuracy location and appearance of defects.

11. TYPES OF NDT :- Visual Inspection Radiography Technique Ultrasonic Technique Magnetic Particle Method Surface Penetration (Dye) Method

12. Visual Inspection Defects which are easily located by visual inspection are surface cracks, roughness swells, tears etc. Visual Inspection is carried out with the naked eye or using a magnifying glass. An inspector carrying out visual examination identifies costing defects and assign their cause to same foundry operation. Visual inspection is simplest, fastest & almost commonly employed, but it needs greater skill on the part of the inspector to locate and identify defects. Only visual inspection may be sufficient for many castings such as manhole covers, drains, counter balance weight etc.

13. VISUAL INSPECTION

14. RADIOGRAPHIC TEST :- High frequency radiations of constant intensity are made to fall on the component to be tested. Some of radiations which passing through the component are absorbed by defects & remaining radiations emerges out from the other side of the metal component. The intensity of transmitted radiations are usually recorded on photographic film. It may be noted that the less darker region represents the perfect portion. The image developed on film is called Radiography. This technique is know as radiographic technique.

15. RADIOGRPHIC TEST

16. This method is used to detect defects in material which with stand high pressure & temperature. Eg. REACTOR, PRESSURE VESSEL Etc.

17. Advantages :- High sensitivity Permanent record on film Adjustable energy level Disadvantages :- High initial cost Power source required

18. ULTRASONIC TESTING :- Ultrasonic inspection is employed to detect and locate defects such as cavities ,internal bursts or cracks etc. For operation ultrasonic wave is introduced into the metal and the time interval between transmission of outgoing waves and incoming waves are measured with the help of CRO. In case of defects exists between the top & bottom casting surface, most of the waves striking this defect will get reflected from defect, and will reach the receiver probe & indicate a echo on CRO screen. This technique is know as Ultrasonic testing.

19. ULTRASONIC TEST

20. Advantages:- It is fast & reliable method of NDT This method of locating flaw is more sensitive than radiography. Low speed and high speed of operation Disadvantages :- Very sensitive to rough surfaces In complex casting the interpretation of oscilloscope traces may not be easy.

21. MAGNETIC PARTICLE INSPECTION :- This method of inspection used an magnetic ferrous casting for detecting invisible surface or subsurface defects. Deeper subsurface defects are not satisfactorily detected because the influence of the distorted lines of magnetic flux on the magnetic particles spread over the casting surface becomes weaker with the distance. The defects commonly are thermal crack, grinding cracks, overlaps, fatigue cracks etc. This method is very simple and easy technique .

22. Magnetic particle inspection

23. Advantages :- Economical & Portable Simple and easy to perform Fast process Disadvantages :- Material tested must be magnetic Demagnetization is necessary Applications :- Applicable to all ferromagnetic material

24. Surface penetrate liquid method 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). The penetrant may be applied to all non-ferrous materials and ferrous materials, although for ferrous components magnetic-particle inspection is often used instead for its subsurface detection capability. 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.

25. Liquid penetrant method

26. ADVANTAGES :- The method has high sensitivity to small surface discontinuities. The method has few material limitations, i.e. metallic and nonmetallic, magnetic and nonmagnetic, and conductive and nonconductive materials may be inspected. Large areas and large volumes of parts/materials can be inspected rapidly and at low cost. Parts with complex geometric shapes are routinely inspected. Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.

27. Disadvantages :- Only surface breaking defects can be detected. Only materials with a relatively nonporous surface can be inspected. Precleaning is critical since contaminants can mask defects. Post cleaning of acceptable parts or materials is required. Chemical handling and proper disposal is required.

28. Eg. Plastics, vessels, tanks etc.

29. FATIGUE ASSESSMENT OF VESSELS IMPORTANT DUE TO VESSELS MAY BE SUBJECTED TO CYCLIC LOADS AND STRESSES. CYCLING CAUSES DUE TO : FLUCTUATIONS IN OPERATING CONDITIONS VIBRATIONS LOADING DUE TO FLOW OF LIQUIDS AND SOLIDS AND FLUCTUATIONS FLUCTUATIONS DUE TO EXTERNAL LOADING FATIGUE ASSESSMENT

30. PRESSURE TEST APPROPRIATE PRESSURE TO BE DETERMINED AS PER: TEST PRESSURE=1.30 [ Pd *Sa/Sn* t/(t-c)] WHERE: Pd = DESIGN PRESSURE Sa,Sn = MAXIMUM ALLOWABLE STRESS AT TEST AND DESIGN TEMP, N/MM2 c=CORROSSION ALLOWANCE T=ACTUAL THICKNESS OF VESSEL

31. TYPES: HYDRO PRESSURE TEST (WATER) PNEUMATIC PRESSURE TEST (AIR)