defects. The manufacturer uses these to
calibrate the NDT system.
Some flaws are exclusively or preferentially detected by one method or
another, so a comprehensive testing
program uses several NDT methods. A
combination of UT and EC is appropriate for small-diameter, medium-wall applications, specifically umbilical lines.
UT and MFL make a suitable combination for large-diameter, heavy-wall applications such as drill pipe, line pipe,
A Setup for Umbilical Lines. Key off-
shore components are umbilical lines,
which are tubulars that run from an off-
shore oil platform to a well or a cluster
of wells. Used for hydraulic lines, chemi-
cal injection lines, and sheaths to protect
electrical cables, umbilicals connect an
offshore oil platform to a subsea mani-
fold system, which is a central oil-collec-
tion point for a cluster of wells.
Umbilicals are extremely long and
usually are tested inline by using an EC
encircling coil. This normally is installed
in a position after inline bright annealing.
Three flaw examples on an umbilical line are a small pinhole detected by EC, but difficult to find with UT (left); a seam defect detected
by EC and UT; and a weld defect on the ID found by UT but not by EC. These results demonstrate the power of using two systems.
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