Page 297 - Pipeline Pigging Technology

Pipeline Pigging Technology

CASE STUDY 2

The second case is that of a 48-in pipeline. The operator was aware that this
pipeline was subject to movement, and is monitoring all changes to the
pipeline. In this case, dynamic forces are known to be affecting the line. The
area of concern is a wave or small wrinkle that is developing on a downhill
section of the pipeline, just prior to a small stream crossing. VPSI has taken this
data over a several-year period to give the operator a compiled report.
The report includes numeric data that represents the different survey runs.
The data is set out by year and quarter the data occurred. Data viewed in this
manner point out the dynamic nature of the area. It also points out that the
area has changed over the 9 years depicted, yet the change does not seem to
be dramatic.
.Numeric data was evaluated in conjunction with slope or vertical displace-
ment. The slope information pointed out that no substantial changes had
occurred. In fact, the data remains identical on all runs (see Figs 11,12,13 and
14).
Fig.l 1 shows the 1989 data on slope and pressure. The saw-toothed line is
the raw data on slope. The smooth line along the bottom of the graph is the
slope as plotted from the raw data; the top line is pressure. Each of the
pipeline bends is marked on the graph at the area in which they occur. A circle
approximately 75% along the line marks the area of the wrinkle.
Fig. 12 shows the data from the 1990 survey. Data from both plots shows
the pipeline slope has not changed. While this is for only two years, data from
preceding years verified that the pipeline is remaining in the same position for
several years.
Fig. 13 shows the computer's ability to manipulate the data as plotted and
change the scale of presentation. Fig. 13 has reduced the amount of data and
increased the scale to bring the operator down on the exact area of interest,
the wrinkle.
Raw data is again plotted in the irregular line in the centre of the graph. The
slope line is now plotted in a grid area of 10-ft by 10-ft increments.
Fig. 14 carries this out to an even larger scale. In this instance, only the slope
is plotted; the grid boxes remain a standard 10ft by 10ft, with the slope
superimposed on the grid.
In addition to the numeric and graphic presentations, the computer can
also generate a three-dimensional look at the wrinkle area. Fig. 15 is a look
along the pipeline at the wrinkle area.
A cross-section of the pipeline can be generated at any given area. The
cross-section in Fig. 16 is the maximum area of deformation in the wrinkle
area.

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