Group Discussion Questions on USFD for Comments/Suggestion

Outcomes of the discussion held at NDT-RDSO/LKO during 143rd Refresher Course. We 52 trainees from different zonal railways  unanimously agreed and satisfied with the following points described as here under:

  1. Painted flange of AT Welds cannot be tested.
  2. Corroded flange of AT Welds cannot be tested.
  3. Alignment of DRT Trolly is frequently disturbed.
  4. Authority letter for DRT/SRT Trolly to be carried in Train and arrangement of road vehicle for USFD Team & M/c.
  5. Limitations of USFD TESTING should be clearly mentioned in USFD Manual.
  6. 45degree Probe can be used to scan Rail from top to bottom.
  7. Insert Guidelines in USFD Manual for Service FB Weld testing and its defect classification with action to be taken.
  8. Consideration of CC+8T; CC+6T factors on fixing the testing frequency .
  9.  Half Moon Deffects are found in initial AT Weld testing.
  10. In the CS3  para no 6.3.2 there should be amendment for the any two or more defects found within 4meter either during USFD Testing of Rails or Welds must be treated as IMR.
  11. Practical & Physical illustration of SEJ Flange testing is not taught as per USFD Manual Para no 11.9.4 at NDT- RDSO/LKO.
  12. During USFD Testing of AT Welds by Tendum Rig, 50mm(approx) from the bottom of the Rail flange towards head remains untested.
  13. In case of USFD Testing by Side Looking Probe, maximum limit to detect Half Moon is upto 10mm from rail flange.
  14. With respect to para 8..16.b(iii) ( CS3 Pnt no 8) the defect signal observed at the weld collar from one end May or May not get confirmed from other end due unfavourable orientation of flaw should be classified as defect.
  15. There is no provision in the USFD Manual for classifican & marking of any visual abnormality found during USFD testing of Rails & Welds.

 

Comments are invited please:

Advertisements

FAQ’s on Ultrasonic tester

General questions about ultrasonic testing

1. What is it?

Ultrasonic nondestructive testing, also known as ultrasonic NDT or simply UT, is a method of characterizing the thickness or internal structure of a test piece through the use of high frequency sound waves. The frequencies, or pitch, used for ultrasonic testing are many times higher than the limit of human hearing, most commonly in the range from 500 KHz to 20 MHz.

2. How does it work?

High frequency sound waves are very directional, and they will travel through a medium (like a piece of steel or plastic) until they encounter a boundary with another medium (like air), at which point they reflect back to their source. By analyzing these reflections it is possible to measure the thickness of a test piece, or find evidence of cracks or other hidden internal flaws.

3. What sort of materials can be tested?

In industrial applications, ultrasonic testing is widely used on metals, plastics, composites, and ceramics. The only common engineering materials that are not suitable for ultrasonic testing with conventional equipment are wood and paper products. Ultrasonic technology is also widely used in the biomedical field for diagnostic imaging and medical research.

4. What are the advantages of ultrasonic testing?

Ultrasonic testing is completely nondestructive. The test piece does not have to be cut, sectioned, or exposed to damaging chemicals. Access to only one side is required, unlike measurement with mechanical thickness tools like calipers and micrometers. There are no potential health hazards associated with ultrasonic testing, unlike radiography. When a test has been properly set up, results are highly repeatable and reliable.

5. What are the potential limitations of ultrasonic testing?

Ultrasonic flaw detection requires a trained operator who can set up a test with the aid of appropriate reference standards and properly interpret the results. Inspection of some complex geometries may be challenging. Ultrasonic thickness gages must be calibrated with respect to the material being measured, and applications requiring a wide range of thickness measurement or measurement of acoustically diverse materials may require multiple setups. Ultrasonic thickness gages are more expensive than mechanical measurement devices.

6. What is an ultrasonic transducer?

A transducer is any device that converts one form of energy into another. An ultrasonic transducer converts electrical energy into mechanical vibrations (sound waves), and sound waves into electrical energy. Typically, they are small, hand-held assemblies that come in a wide variety of frequencies and style to accommodate specific test needs.

7. What is an ultrasonic thickness gage?

An ultrasonic thickness gage is an instrument that generates sound pulses in a test piece and very precisely measures the time interval until echoes are received. Having been programmed with the speed of sound in the test material, the gage utilizes that sound velocity information and the measured time interval to calculate thickness via the simple relationship [distance] equals [velocity] multiplied by [time].

8. How accurate is ultrasonic thickness gaging?

Under optimum conditions, commercial ultrasonic gages can achieve accuracies as high as +/- 0.001 mm (0.00004″), with accuracies of +/- 0.025 mm (0.001″) or better possible in most common engineering materials. Factors affecting accuracy include the uniformity of sound velocity the test material, the degree of sound scattering or absorption, the surface condition, and the accuracy and care with which the instrument has been calibrated for the application at hand.

9. Who uses ultrasonic gages?

A major use for ultrasonic gages is the measurement of remaining wall thickness in corroded pipes and tanks. The measurement can be made quickly and easily without needing access to the inside or requiring the pipe or tank to be emptied. Other important applications include measuring the thickness of molded plastic bottles and similar containers, turbine blades and other precision machined or cast parts, small diameter medical tubing, rubber tires and conveyor belts, fiberglass boat hulls, and even contact lenses.

10. What is an ultrasonic flaw detector?

Sound waves traveling through a material will reflect in predictable ways off of flaws such as cracks and voids. An ultrasonic flaw detector is an instrument that generates and processes ultrasonic signals to create a waveform display that can be used by a trained operator to identify hidden flaws in a test piece. The operator identifies the characteristic reflection pattern from a good part, and then looks for changes in that reflection pattern that may indicate flaws.

11. What kind of flaws can you find with one?

A wide variety of cracks, voids, disbonds, inclusions, and similar problems that affect structural integrity can all be located and measured with ultrasonic flaw detectors. The minimum detectable flaw size in a given application will depend on the type of material being tested and the type of flaw under consideration.

12. Who uses ultrasonic flaw detectors?

Ultrasonic flaw detectors are widely used in critical safety-related and quality-related applications involving structural welds, steel beams, forgings, pipelines and tanks, aircraft engines and frames, automobile frames, railroad rails, power turbines and other heavy machinery, ship hulls, castings, and many other important applications.

13. What other types of instruments are available?

Ultrasonic imaging systems are used to generate highly detailed pictures similar to x-rays, mapping the internal structure of a part with sound waves. Phased array technology originally developed for medical diagnostic imaging is used in industrial situations to create cross-sectional pictures. Large scanning systems are used by the aerospace industry and metalworking suppliers to check for hidden flaws in both raw materials and finished parts. Ultrasonic pulser/receivers and signal analyzers are used in a variety of materials research applications.

14. Why Flashbutt welding is preferred than other types of Welding?

Flash welding is an electrical resistance based butt welding process and has the following advantages:

  • It can be made over the whole joint area in a range of section sizes and complex shapes (for e.g from bicycle wheel rims to railway rails), although the sections to be joined should normally be closely matching. Mitre joints can also be formed, such as in welded metal window frames.
  • A wide range of materials can be welded including steels, stainless steel, aluminium alloys, nickel alloys and titanium.
  • A solid phase, forge weld is made, and any molten metal and contaminants formed at the interface during heating are squeezed out into the upset. Thus, solidification cracking and porosity are not normally an issue.
  • The process is normally automatic or semi-automatic and process monitoring can provide an indication of weld quality.