Inspectioneering Journal

Effective MOC — The Vital Link in Process Piping Integrity

Part 3

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


In the Jan/Feb issue of the IJ, I mentioned how important the Management of Change (MOC) process is when it comes to maintaining safe, leak-free piping systems; stating that we in the inspection business cannot do it alone; that is, we taint the integrity of piping systems without a lot of help from operating personnel and operations support engineers. I went on to say that we cannot inspect integrity into piping systems. MOC is a critical link in the whole process of maintaining the mechanical integrity of process piping systems. In this article, I'm going to expand upon that theme a bit.

In the "perfect world" of inspection, after several hundred hours of operation, we make an accurate inspection of a piping system, calculate an accurate corrosion rate and then we know precisely when the corrosion allowance will be gone and therefore when we will need to schedule pipe replacement. So, in that "perfect world," we don't need to make any other inspections because we already know exactly how long that pipe will last. Now obviously no one lives in that perfect world, and unfortunately, many of us are farther from it than we should be. Hence, we build in a safety factor on inspecting at half life or some predetermined maximum interval (per API-570 Process Piping Inspection Code).

But an even more important safety factor for piping inspection is an effective MOC process. Many operating personnel do not understand that we have established the next inspection interval, based on calculated corrosion rates from thickness data taken during the last piping inspection (condition-based intervals). Many are under the mistaken impression that we are "crawling all over their pipes" with our thickness gauges and because of that we will find all changes in corrosion rates and therefore, we will be able to schedule piping replacement whenever necessary. So it's time that we enlighten our brothers/sisters in operations about how the piping inspection scheduling process really works.

Most operators do not understand that the economy of condition-based inspection, as well as the older style approach of time-based inspections, is highly dependent upon an effective management of change process. Note the importance of the word "effective" in the previous sentence. Too many sites have excellent MOC procedures and ineffective MOC processes.

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