A Discussion on the Piping Thickness Management Process: Part 4 – Collecting Quality Thickness Data
Piping failures still represent a frustrating and ongoing problem for processing plants (example in Figure 1). Failures are still commonly reported and contribute to large losses. In the author’s experience, piping represents the highest percentage of fixed equipment failures in petroleum refining. There are of course many factors within a pressure equipment integrity program (PEIP) that can contribute to piping integrity problems, including design issues, operating window compliance, management of change issues, etc.
Five year loss totals in the refining sector have continued to trend upwards over the last few years. While the 2000-2006 period presented a drop in losses, the increasing trend is unlikely to have abated. Piping failures or leaks (corrosion or incorrect metallurgy) and start-up and shut-down events continue to be significant causes.
This article is the fourth in a series of articles that will focus on one critical sub process within a PEIP that is key in managing the integrity of process piping: Collecting Quality Thickness Data. These articles will discuss what constitutes an effective piping thickness monitoring process and will present several practices that may be new to some readers, but these practices have produced beneficial results in other major piping reliability programs. The first article (September/October 2012 Inspectioneering Journal) provided an overview of this process as outlined in Figure 2. The second article (November/December 2012 Inspectioneering Journal) discussed the considerations that factor into determining the number and position of corrosion monitoring locations (CMLs). A third article (January/February 2013 Inspectioneering Journal) discussed the benefits and limitations of using ultrasonic (UT) and radiography (RT) thickness data collection techniques. This article will discuss the elements of ensuring that the thickness measurement inspection (TMI) provides quality thickness data as part of the thickness management process (TMP) such that the data is non-spurious and useful in assessing piping condition accurately.
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