Basic Nondestructive Testing - The C&S Companies

1 Basic Nondestructive Testing for EXPO 2012. by Neville W. Sachs, Applied Technical Services New York ATSNY 2012 1. What we plan to cover 1. Definition of Nondestructive Testing 2. Some philosophy on why it is helpful and the major pitfalls 3. Basic theory 4. Explanations of common techniques 5. Demonstrations of common analysis techniques ATSNY 2012 2. Nondestructive Testing (NDT). Also known as Nondestructive examination (NDE). Involves inspection and analysis of machinery or components without affecting the operation or the properties of the subject. (As opposed to a tensile test or other destructive test such as sectioning.). ATSNY 2012 3. From the ASNT Website (American Society for Nondestructive Testing ). What Is Nondestructive Testing ? Nondestructive Testing asks Is there something wrong with this material? . Nondestructive Testing (NDT) has been defined as those test methods used to examine an object, material or system without impairing its future usefulness.

2 ATSNY 2012 4. The British View (BINDT). Non-destructive Testing is the branch of engineering concerned with all methods of detecting and evaluating flaws in materials.. The essential feature of NDT is that the test process itself produces no deleterious effects on the material or structure under test.. The subject of NDT has no clearly defined boundaries . ATSNY 2012 5. A Brief History Formal NDE dates back to early railroad days when a mixture of oil and talc were used to detect cracking in axles and wheels. Since then science has developed a wide range of tools and abilities to noninvasively detect problems before they become disasters. ATSNY 2012 6. Wikipedia says Nondestructive Testing is . Acoustic emission Testing (AE or AT) Magnetic resonance imaging (MRI) and NMR. Blue Etch Anodize (BEA) spectroscopy Dye penetrant inspection Liquid penetrant Testing (PT or LPI) Metallographic replicas [7] [8].

3 Near-infrared spectroscopy (NIRS). Electromagnetic Testing (ET) Optical microscopy Alternating current field measurement (ACFM) Positive Material Identification (PMI). Alternating current potential drop measurement (ACPD) Radiographic Testing (RT) (see also Industrial Barkhausen Testing radiography and Radiography). Direct current potential drop measurement (DCPD) Computed radiography Digital radiography (real-time). Eddy-current Testing (ECT) Neutron radiographic Testing (NR). Magnetic flux leakage Testing (MFL) for pipelines, tank floors, and wire rope SCAR (Small Controlled Area Radiography). Magnetic-particle inspection (MT or MPI) X-ray computed tomography (CT). Remote field Testing (RFT) Scanning electron microscopy Ellipsometry Surface Temper Etch (Nital Etch). Ultrasonic Testing (UT). Guided wave Testing (GWT) ART (Acoustic Resonance Technology).

4 Hardness Testing Electro Magnetic Acoustic Transducer (EMAT). Impulse excitation technique (IET) (non-contact). Infrared and thermal Testing (IR) Laser ultrasonics (LUT). Thermographic inspection Internal rotary inspection system (IRIS). ultrasonics for tubes Laser Testing Phased array ultrasonics Electronic speckle pattern interferometry Time of flight diffraction ultrasonics (TOFD). Holographic interferometry Time of Flight Ultrasonic Determination of 3D. Low coherence interferometry Elastic Constants (TOF). Profilometry Vibration Analysis Visual inspection (VT). Shearography Pipeline video inspection Leak Testing (LT) or Leak detection Corroscan/C-scan Absolute pressure leak Testing (pressure change) IRIS - Internal Rotary inspection System Bubble Testing 3D Computed Tomography Halogen diode leak Testing Industrial CT Scanning Heat Exchanger Life Assessment System Hydrogen leak Testing RTJ Flange Special Ultrasonic Testing Mass spectrometer leak Testing Tracer-gas leak Testing method Helium, Hydrogen and refrigerant gases ATSNY 2012 7.

5 So, going back to the ASNT website, these are the common NDT. techniques Acoustic Emission Eddy Current Liquid Penetrant Magnetic Particle Ultrasonic Testing Visual inspection Vibration Analysis Radiography (X-ray). Also common are: Infrared Thermography Hardness Testing ATSNY 2012 8. Your Personal NDT. When you go to the market to select fruit or veggies, what do you do? How do you make your choice? If your car is making a new strange noise, what do you do? Do you ever glance at your car tires to see if they are soft? ATSNY 2012 9. The goal . A. Look at it without causing a damaging interruption B. Use the test information to form a plan ATSNY 2012 10. NDT in everyday life Would you rather have an MRI - or should we do exploratory surgery for that knee problem? Would you prefer an EKG or exploratory surgery? For both of these, consider the possible costs and the possible benefits.

6 ATSNY 2012 11. The goal of NDT is to analyze a piece of material, without damaging its performance capabilities, and then use that information to predict future performance. The graph below shows leaks in the roof of a process vessel. (Replacing the vessel will cost about $50,000,000. Routine inspections of a vessel and take about a year.). 300 with stress corrosion cracking Number of leaks Roof leaks 200. vs. inspection date 100. 0 4 8 12 16 20. Years from vessel installation ATSNY 2012 12. The goal . Look at it without causing a damaging interruption So, not only can we look at and inside pieces, but we want to do that without causing an interruption. Then a question arises - Do humans really commit that many errors? ATSNY 2012 13. Human Error Experts say the average person makes six significant errors per week. BUT, our surveys show the typical industry person believes they make a significant error about once every FIVE months ATSNY 2012 14.

7 In 23 years of doing industrial training programs and asking people to compare their skills with others in the same job, only 37 people have rated themselves as below average! ( 23 years x 15 seminars/year x 15 people/seminar = 5100 students 37/5100 = ). For the last six years we have also asked people to rate their safety awareness. Only TWO have said they were below average!!! ATSNY 2012 15. How Often Do Human Errors Happen? (From Chemical Engineering Magazine, McGraw Hill, NY,NY). Industrial Activities Critical routine task - 1/1000. Non-critical routine task - 3/1000. General error rate for high stress rapid activities - 1/4. Non-routine operations (startup, maintenance, etc.) - 1/100. Checklist inspection - 1/10. General Human Error of Observance - 1/50. of Omission - 1/100. ATSNY 2012 16. How Often Do Human Errors Happen?

8 (From Chemical Engineering Magazine, McGraw Hill, NY,NY). Industrial Activities Critical routine task - 1/1000. Non-critical routine task - 3/1000. General error rate for high stress rapid activities - 1/4. Non-routine operations (startup, maintenance, etc.) - 1/100. Checklist inspection - 1/10. General Human Error of Observance - 1/50. of Omission - 1/100. ATSNY 2012 17. The "Reliability Bathtub". Failure Probability Normal Run Period Infant Mortality Wear out Wear out - Time (log scale). A function of Infant Mortality the original design The period right after Normal Run Period the machine is started. The long stable time when These failures are successful operation can be usually related to errors expected. Failure in this time in assembly. is usually from unexpected wear or a change in operating conditions. ATSNY 2012 18.

9 So, what % of equipment actually suffers from Infant Mortality It really depends on the training of the installation personnel and their training and care. There is data from studies of maintenance activities around the country and have seen it range from a low of about 5% to as high as 22%! Several North American studies have shown the average is about 14% substantially defective! ATSNY 2012 19. The most important benefits of NDT are that it allows us to inspect materials and machinery: 1. Without introducing infant mortality. 2. Without damaging the material. ATSNY 2012 20. And .. The data shows that: All humans make frequent errors. We tend not to recognize those errors. The benefit of NDT is that it can find defective material/equipment without damaging the pieces and without the interruptions that increase the probability of human error.

10 ATSNY 2012 21. Common Uses for NDT. Product and/or material quality assurance Examples Run-in test on a new vehicle, cleanliness of steel Component/machine condition evaluation Example inspection of a ski lift component or an elevator rope. Predictive method - Vibration analysis on motors, and pumps, infrared inspection of transformers. ATSNY 2012 22. The PE's Challenge We are asking technicians to conduct an inspection . They are not engineers and, by definition, must have criteria to inspect to, , have to know what is considered a defect. ATSNY 2012 23. So, before we ask for a specific NDT, we have to know what to ask for! Q. What is the difference between a flaw and a defect? A. Almost all materials have lots of flaws. When the flaw impacts the performance of the material, it becomes a defect. ATSNY 2012 24. Important Terminology - Defects and Flaws All parts have flaws of some magnitude but the parts are not necessarily defective.