Inspectioneering Journal

Interview with Dr. David Wang - Primary NDE Researcher

By Greg Alvarado, Chief Editor at Inspectioneering. This article appears in the July/August 2001 issue of Inspectioneering Journal.

Inspectioneering caught up with Dave Wang at the American Petroleum Institute’s (API) Spring 2001 Refining meeting in Atlanta, Georgia. We spent some time, near the pool at a break between meetings, discussing Dave’s background, experiences and the future of NDE from his perspective.

Mr. Wang has primary responsibility for NDE development and implementation for Shell/Equilon/ Motiva, supporting a vast network of downstream and upstream facilities/ assets around the United States. Dave and I have known each other for many years, probably as long as he has been at Shell/Equilon. I have always known him to be one of the most imaginative, respected and productive professionals in this field with many accomplishments to his name.

We sometimes discuss the current state of the art in NDE as applied to refinery and chemical plant equipment, often covering the current quality of services and technology available. It seems we always have a leaning toward NDE as it relates to fitness for service and how we may use the data, sometimes on it’s own merit and often in conjunction with complimentary approaches.

David has many accomplishments to his credit including developing and patenting the Advanced Ultrasonic Backscattering Technique (AUBT) for detection, characterization and quantification of hot hydrogen attack damage in mild and low alloy steels. This method broke the barrier in being able to distinguish between real damage and other, more innocuous anomalies like porosity and slag in parent plate and in welds and weld heat affected zones.

Dave, how long have you been at Shell/Equilon and when did you know you would be working as a professional in the field of NDE?

Dave Wang (DW): I have been at Shell/Equilon since I graduated from the Ohio State University with a Ph.D. in Welding Engineering, majoring in NDE . Prior to that, I had attended the National Taiwan University where I earned an MS degree in Materials Science and Engineering following my undergraduate degree in Metallurgy and Materials Engineering from the National Chang-Kung University in Taiwan.

Because my MS and BS were all in Materials Engineering, I didn’t know that I might work as a professional in the NDE field until I went to the Ohio State University. I knew for sure that I would be working as an NDE professional when I accepted the position with Shell Development in late 1990. So it was something I had never dreamed of prior to it happening.

That seems to be typical of the vast majority of people I talk with in our field. We evolve toward the NDE field. Can you tell me a little about who you admired as a youth?

DW: I was impressed by great military leaders who possessed the ability to pull a nation or nations together then move them in the same direction, e.g., Alexander the Great and Napoleon. I also admire people who can communicate their vision and make a difference. Our ex-President Bill Clinton is a good example. I feel he is a great communicator. But I do want to make it clear that I am not talking about his moral standards, which I do not admire. Another good example is John Reynolds, at Equilon, who has great communication skills and an amazing influence in the refining and chemical industry.

Does the appreciation of these qualities and abilities affect the way you approach work today?

DW: Of course. I get excited about having vision for where technology and solutions need to go in the future. I then find it a challenge to bring people together, both within Equilon and outside of Equilon, and earn their buy-in as we find the solutions. The current PERF projects are great examples of where this is happening for the refining and chemical community.

What are the PERF projects?

DW: PERF is an acronym standing for Petroleum Environmental Research Forum. This is a mechanism originally established by a consortium of refining and chemical companies which allowed them, as a group, to pool their resources to overcome common problems, initially focused on environmental issues. It was extended in 1995 to include projects addressing mechanical integrity issues. Some examples of the projects:

  • 95-01: Advance NDE for Piping Inspection
  • 95-07: Aging Hydroprocessing Reactors
  • 95-10: Advanced NDE for Heat Exchanger Tube Inspection
  • 95-11: Advanced Acoustic Emission for On-stream Inspection
  • 96-03: NDE Hardware and Operator Evaluations

I have the privilege of leading PERF project 95-11 on acoustic emission as the Technical Coordinator. PERF NDE meetings typically happen in conjunction with API refining meetings, once in the spring and once in the fall of the year.

As you also know, in another venue the API have started a qualification demonstration program for NDE operators providing services to refining and chemical plants. API has started the program with manual UT flaw detection. Other techniques will follow. I am Equilon’s representative to the steering group. Others members in the steering group include Chevron, ExxonMobil, BP, etc.. CP Hsiao with Chevron is chairing the group.

It is important that we assure an acceptable level of quality for plant inspections. That is the reason for this group’s efforts. We need to know how much we can depend on the inspection results when the results say that we have corrosion or cracking in a vessel or pipe and, just as important, when they tell us there is no damage. When damage is found, we often submit the quantitative information such as wall loss or cracking location, length and depth to a fracture mechanics engineer, now often employing API RP 579 Fitness for Service (FFS) methodology, to determine current safe operating limits and future limits. API 579 affords our industry better assessment for making run, repair or replace decisions.

The person performing the FFS calculation relies heavily on the inspection information. The more accurate the NDE information, the more meaningful results we can get from the FFS assessment.

This is an area where we see efforts from time to time to develop new NDE techniques to perform field measurements to ascertain actual remaining physical properties of equipment. A vessel may be made of steel materials of a particular grade which have property ranges defined by ASTM or ASME. Firstly, the owner user may not have the original materials certifications showing test results for that specific heat and the possible range of properties could make a difference in the FFS calculations. Secondly, materials often degrade over time, especially materials exposed to high temperatures, such as furnace tubes or reactors, and cyclic loads whether mechanical fatigue or temperature. Thirdly, residual stresses in weld heat affected zones, from original fabrication and/or repairs may play a part in the FFS assessment and may not be known.

If we know what these values actually are, the FFS analyst would not have to resort to using overly conservative figures. With accurate information the FFS answer would be more precise so better run, repair, replace decisions could be made. This provides distinct safety and business advantages to the owner user. Can you see the importance the role of NDE has in the process industry?

Absolutely! I can see why you receive so much gratification from the work you do. Can you give the IJ readers another example of technology you have developed?

DW: Piping support inspection using an accurate Lamb wave sizing algorithm. I have developed an algorithm using Lamb waves to quantify the extent of piping corrosion at the supports without lifting the pipe. This is especially valuable when there is a concern about potential damage in the piping under a pipe support. With this, one can inspect for damage. Measure the damage extent and decide what to do, without having to remove the support or move the pipe. The technology has been licensed to an inspection service vendor, which has been inspecting piping supports in refineries and chemical plants with successful results.

I also like the challenges presented by equipment in wet H2S service. I really believe that external NDE methods are the way to go. We have made a lot of progress with methods like automated ultrasonic techniques to inspect equipment externally for internal damage. For example we can pick selected areas, based on past experience and corrosion and fabrication knowledge, to look for and measure cracking and corrosion from the exterior at welds and heat affected zones without going inside.

In the past we would go inside and remove the protective oxide film to perform WFMT. Some would even go to the extent of removing tray supports to perform WFMPT (wet fluorescent magnetic particle testing) of the fillet weld areas looking for wet H2S related damage. This can all be done from the exterior while the vessel is in service. The benefits are: no removal of the protective internal films, better planning/preparation for turnarounds by finding damage up front and not needing to enter unless repairs need to be performed, and minimizing the risks associated with placing people inside vessels.

If you are going to inspect internally, consider use of ACFM in lieu of WFMPT. Similar to WFMPT, ACFM can find through-wall-oriented cracks, e.g. sulfide stress cracks. Unlike WFMPT, ACFM requires minimal and sometimes no surface preparation. Rough ballpark, I believe ACFM is about 1/3 the cost to perform compared to WFMPT when including the cost of surface preparation.

Dave, we have gone over some very important territory. A lot of things have been accomplished. Where do you see the industrial NDE community going in the future?

DW: For our industry, I see strong needs for more on-stream, non- intrusive, global, and rapid inspection techniques. The inspection reliablity needs to be quantified and tied to FFS and Risk-based Inspection (RBI) decision making. We need good NDE training programs not only for NDE operators but also for owner/users. NDE operator qualification for specific applications is also an important area that we need to work on. Some of the above are already getting a lot of attention. Noticable advances/improvements have been made in the last few year. I would expect continuing development/ improvement made in the same, important areas at least in the next five years.


Dr. David Wang has been married to Paula since 1988 and is a proud father of a daughter, Dara 8 years old and a son, Gradey 5. They reside in the Houston area. Thanks sharing your thoughts and views with the IJ community.


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