Understanding API ICP653 Reading 7-Worksheet-04 Part1

6.4.3 Alternative Internal Inspection Interval
For unique combinations of service, environment and construction, the
owner/operator may establish the interval using an alternative
procedure. This method includes:
a. Determining bottom plate "t".
b. Consideration of environmental risk.
c. Consideration of inspection quality.
d. Analysis of corrosion measurements.
As an alternative an RBI program may be used.
NOTE: Must be documented and made part of permanent record.
6.5 Alternative to Internal Inspection to Determine Bottom "t"
In cases where construction, size or other aspects allow external access to
bottom, an external inspection (in lieu of internal) is allowed to meet
requirements of Table 6-1. Documentation also required.
Charlie Chong/ Fion Zhang