Latest Branch News

News from the Institute Branches – December 2017 

| South Wales Branch
Sewers to the sky

Steve O’Brien reports

The South Wales Branch convened for its October 2017 meeting at the Village Hotel near Cardiff, for a rather cryptically-titled presentation by Gary Luckett about the real-life challenges of introducing advanced inspection techniques into applications in which NDT has not previously been utilised.

Once we were all comfortably seated, Gary started the presentation with the description of an issue caused when a major UK manufacturer of large quarry vehicles changed its steel supplier. This resulted in the unexpected and dramatic failure of gears due to the presence of aluminium oxide inclusions, caused by poor quality control of the steel billet. He then moved on to a detailed explanation of how phased array inspection was developed, using the current phased array documentation available, for example HSE documents, code cases, journals/papers, flat-bottomed hole standards drilled into test specimens, etc, to meet the client’s requirements for defect sensitivity, coverage, adaptability, speed and repeatability in the inspection of gears during the manufacturing process.

Next, Gary put up a slide posing the following question: How are a Boeing 737 and a sewage tank similar? Moving on to the next slide, we discovered that a sewage treatment plant reported that a storage tank for raw product had burst due to cracking between rivets that led to the separation of the plates. An inspection company was contacted to develop a test to detect cracks propagating between the rivets that was quick, due to the large inspection area, and also straightforward to analyse. The solution was to leverage a well-known inspection technique from the aerospace sector (the Boeing 737 scribe line inspection), which is a phased array sectorial scan using the known reflectors to verify the condition of the plate.

After the presentation, a question and answer session and discussion took place, where we discovered that a member of the Branch (Meurig Davies) had been involved in the development of this particular inspection technique and was able to expand further on the information Gary had just provided.

Many thanks to Gary for offering a very interesting presentation.

| Yorkshire Branch
Material identification and the use of XRF analysers

John Moody reports

Attendance at the meeting in November was very good, with both old and new faces in the audience. Gary Luckett of Olympus demonstrated his obvious passion for material identification and the use of XRF analysers. The most important thing taken from this presentation is the need for an understanding of the safety requirements associated with using this equipment and how important it is to understand the capabilities and limitations of the equipment.

The instrument emits 20,000 mSv/hr at 0.1 m, so checking the purity of the gold fillings in either your own or somebody else’s mouth should not be attempted. At 1.3 m you are looking at a dose of 1 mSv/hr, so you should never hold the item under test in your hand. Using the instrument on a wooden desk while sitting there is also a ‘no no’ as there is a significant amount of radiation penetrating through and being absorbed by your knees, thighs or other parts. In the UK, the IRR 99 regulations are applicable and most other countries probably have regulations that cover the use of these instruments.

The process works by knocking protons out of orbit and the emission of characteristic secondary (or fluorescent) X-rays. Each element generates a different wavelength and these are captured and processed by the instrument. 25 to 30 elements can be checked simultaneously and a reading is given on the screen showing the chemical analysis and probable alloy. The material is not damaged and coating thicknesses can be checked; it sounds great providing it is used safely.

All we have to do is take it out of the box, make sure the battery is charged, respect the safety requirements and off we go. However, in reality, it is not that simple. Many machines can only be calibrated by the manufacturer or a trained person, the machine can be assessed by the operator on a known reference specimen and temperature correction can be made. Without an understanding of the capabilities, gold and tungsten can be confused. A quick shot (one second) may only give a rough idea of the chemistry in the sample but a longer shot (three seconds or more) improves accuracy, as explained by standard deviation and one sigma against three sigma sampling. Carbon is one of the elements that is not currently analysed but there are developments that may enable this in the future. The surface condition can also lead to incorrect readings, along with dirty windows on the instrument. If the measured sample does not meet the specification, the operator needs to be able to assess if there are other factors affecting the results before rejecting the sample.

Gary gave a practical demonstration of the equipment, showing how it can measure the coating thickness on a turbine blade and the chemistry of other items. He also mentioned some of the other applications that he has been involved with, including a stuffed polar bear. Please contact Gary directly for this story and more information on the capabilities of the equipment. It must be noted that there are other providers of this type of equipment.

Many thanks to Gary, Olympus and IMechE ARL for making the event a success.