POWER February 2016 - 44

OPERATIONS & MAINTENANCE
3. Pipeline journey. An artist's rendering of a SmartBall traversing the 16-in line shows acoustic signatures corresponding to a leak (left) and
a fully developed gas or air pocket (center). Courtesy: Pure Technologies
way. The Pure analysts cross-check the data
against signals from the 10 transceivers to
pinpoint the location of any anomaly. They
further evaluate the acoustic signature to estimate
the approximate magnitude of a leak.
Pure categorizes leaks as small (0 to 2 imperial
gallons per minute, gpm), medium (2 to
10 gpm), or large (greater than 10 gpm).
The Pure team detected no leakage or
other cause for alarm in the cooling line.
However, they did find acoustic anomalies
that indicated pockets of gas trapped
in 10 locations where the elevation of the
run changed (Figure 4). These typically
displayed a " hydraulic jump " at the point
where the pipe descends in elevation, creating
a turbulent flow. This turbulence, together
with frequent wet/dry cycles caused
by changes in flow, puts these areas at higher
risk of failure. We therefore marked those
10 locations to help us keep an eye on them
at regular intervals.
Electromagnetic Sensing for PCCP
Circulating Water Line
We consulted the Structural Group for the
PCCP circulating water line as well, and they
again retained Pure Technologies to perform
the inspection. This time, Pure brought an
electromagnetic (EM) device to survey the
PCCP that makes up our 84-inch-diameter
circulating water line.
The EM technology works by inducing
a varying electrical field on the prestressing
wires in the concrete and measuring the
corresponding magnetic field response. The
Pure team focused primarily on the prestressing
wire-the structural component that provides
the pipe's strength. They surveyed each
pipe section to identify anomalies associated
with any zones of wire damage.
44
www.powermag.com
POWER | February 2016
The equipment consists of a transmitter
coil that generates the electrical field and a
receiver coil that picks up the induced response.
As the equipment is moved through
the pipeline or along an external pipe surface,
a data logger records the data.
To understand how the data signal responds
in various conditions, the Pure team
performed calibration scans on pipes similar
to GRE's. From these, they created a calibration
curve, which they then applied to the
" distress " signals measured in GRE's pipeline
to quantify the number of wire breaks in
each distressed region.
Once they'd established the baseline signal,
they performed additional scans on the pipe under
varying wire break conditions to determine:
■ The ability of the system to detect the
presence of broken wires.
■ The resolution of the system when the
number of broken wires is changed.
■ The optimal system settings that should be
used for that particular pipe.
The team then incorporated the calibration
curve into their analysis software. This
made it possible for their analysts to measure
a distress signal and compare it against the
curve to quantify the number of wire breaks
represented by that signal.
The conveyance used by the Pure team to
4. Gas pocket detected. The acoustic signature of a fully developed gas pocket in the
line typically shows a broader, less-defined array of signals than the abrupt spike of a leak's
signature. Courtesy: Pure Technologies

http://www.powermag.com

POWER February 2016

Table of Contents for the Digital Edition of POWER February 2016