Pipeline operators worldwide have implemented integrity management programs in an effort to improve
operation and maintenance efficiency along with continued safe operation of their systems. Several
types of monitoring and data collection activities are incorporated into these programs, with inline
inspection tools providing data for detection and quantification of features that may impact the integrity
of the pipeline system. Magnetic flux leakage tools are among the most widely used in pipeline
systems, typically providing information for metal loss features. The tool configurations being offered
have been expanded in recent years to allow multiple data sets to be collected concurrently. Magnetic
flux leakage tools incorporate fields that are axially aligned with the pipe for detection of general
corrosion type features. For extremely narrow metal loss or certain classes of seam weld features,
tools with fields that are circumferentially aligned or transverse to the pipe axis are used. Presently,
multiple independent inline surveys are required to adequately address each of these feature classes.
Providing the ability to collect both of these data sets in a single survey would allow operators to
minimize the number of surveys required to address metal loss features that may be present within
pipeline systems. In addition to fewer surveys being required, the concurrent acquisition of multiple
data sets will minimize the time required to perform comparisons of the data sets from each of the
surveys. This paper will discuss the results obtained from test data when the magnetic fields are
applied at an oblique angle to the main axis of elongated metal loss features. Several classes of
features have been chosen for evaluation, including extremely narrow axially oriented features
Key words: magnetic flux leakage, oblique, pipeline