Inspectioneering Journal

Piping Inspection - Improving Thickness Data Taking Accuracy

Part 2

By John Reynolds, Principal Consultant at Intertek. This article appears in the March/April 1997 issue of Inspectioneering Journal.
This article is part 2 of a 4-part series.
Part 1 | Part 2
Part 3 | Part 4


This is the second in a series of articles on piping inspection. In the last article, I enumerated four inspection issues that I believe contribute to inadequate piping mechanical integrity in the hydrocarbon process industry.

  1. Unreliable, inaccurate thickness data measures by individuals that were not adequately trained, skilled, or qualified.
  2. Entering data of questionable quality into thickness data software programs that produce poor results from poor data.
  3. Piping thickness data being entered into inspection records and then being "ignored" or otherwise not being properly analyzed and/or acted upon.
  4. Not inspecting in the right places and not using the right inspection techniques to find thinning, especially localized corrosion.

Let's begin to deal with the first two issues. If you accept thickness data from inspectors and/or UT technicians who have had no significant training or knowledge base on the important issues that cause inaccurate measurements, then you very likely may be getting data that vary up to 30-40 mils (thousands of an inch) from actual thickness on standard wall, 6 inch diameter pipe. When you enter that kind of data into your records, at worst you get a feeling of confidence that everything is fine, when in actuality you have a significant corrosion problem, and at best you get a feeling that you have high corrosion rates and you end up replacing piping that does not need replacement or you just end up wasting resources inspecting more often than is really necessary. Neither of these are particularly desirable outcomes, especially when you consider that it costs just as much to take bad data as it does to take good data.

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