New Appendix G of API-653 Provides for Tank Bottom Inspections Qualification Guidelines

By Vincent A. Carucci

Aboveground storage tank bottoms must be periodically inspected and assessed for their integrity. This will generally set the required interval for internal tank inspection. During this inspection, the entire bottom should be visually examined for holes, cracked welds, generally corroded or pitted areas, and previously repaired areas. Additional inspection methods will also typically be used to obtain all the data needed to assess the integrity of the bottom. This can include:

API-653, Tank Inspection, Repair, Alteration and Reconstruction, does not explicitly state the inspection procedures that must be used, nor their extent. These are left up to the owner/operator to decide. However, with Addendum 1 issued September 2003, API-653 contains a new Appendix G that provides guidance for qualifying both tank bottom examination procedures and the personnel who perform tank bottom examinations.

The owner/operator may apply the Appendix G guidelines as written, or modify them to suit their particular applications and needs. The introduction of Appendix G uses the words “guidelines” and “guidance” in describing the information contained in it. However, it is clear that the intent is to follow these guidelines, or at most, adapt them for specific situations while still meeting their intent.

All tank inspections are important in order to evaluate the tank’s structural integrity. However, bottom integrity evaluation and the inspection data that are needed to conduct it are clearly the most important factors to “get right” for obvious reasons.

With the advent of API-653 in 1991, much more attention has been paid to tank inspection and integrity evaluation in general and the bottom in particular. There has thus been a large increase in the number of individuals and companies performing tank inspections. Technology improvements and inspection techniques have also kept pace with this increased demand. Because of all these factors, it is important that qualified inspection tools, procedures, and personnel are used in tank bottom examinations. This is where Appendix G comes in.

The approach that Appendix G uses to present its guidelines is similar to that used with welding procedures and welder qualification. Some of the same terminology is also used. The following highlights the overall structure and some of the information contained in Appendix G. Refer to Appendix G for complete details.

Appendix G is an important and welcome addition to API-653. Its use will go a long way toward improving the reliability of tank bottom inspection data.