developing necessary pipeline documentation keeps operators
in compliance with American National Standard Institute
(ANSI) codes. Documentation is necessary not only for records
review, but whenever welding is performed, replacement
pipe materials are obtained, or a pipeline is being reviewed
for re-rating, Kraska explains. Welding on a pipeline without
thorough knowledge of the materials involved, the correct
welding procedure, or the composition of welding filler metal
is also an ANSI violation, he adds.
But there is also a positive financial case to be made in
support of the regulation, and it goes like this: operators
who have had to downgrade pipeline pressure for lack of the
records that would justify higher pressure are losing money.
By performing PMI, they may find out that their pipelines
can actually accommodate higher pressure and, therefore,
increased capacity.
And while the PHMSA ruling only applies in the US, similar
benefits could accrue for Middle Eastern and Russian natural
gas transmission and the Canadian oilsands. In addition,
verifying higher operating pressures is considered essential for
the safe operation of pipeline reversals and conversions, two
activities that are now occurring worldwide.
NDE techniques can save time and money
In engineering, project management and other disciplines,
the triangle is used to represent the interdependent nature
of certain attributes, like time, cost and scope. The triangle
is also useful when it comes to considering positive material
identification.
In PMI, one side of the triangle represents material
strength, another is the load or pressure, and the last
side symbolises defects. In order to keep the triangle
from collapsing, all three have to relate to one another
appropriately.
For example, strength is determined by the ability to
withstand pressure. Defects can alter both strength and load.
And pressures above system limits can cause defects to grow.
However, a lack of knowledge about any side can upset
the overall equilibrium. With appropriate information,
operators can keep their triangle in balance.
For generations, operators have had to rely on destructive
techniques to identify pipeline materials and MAOP, utilising a
time-consuming, costly procedure that involved cutting out a
coupon and sending the piece away to be lab-tested.
But not any longer. That is because the positive material
identification process offered by global pipeline integrity
services provider T.D. Williamson (TDW) utilises multiple
non-destructive technologies that eliminate the need for
cutting into the pipeline and can be completed while product
continues to flow. TDW’s patent-pending PMI can provide a
high level of accuracy with less effort, lower total cost and
shorter turnaround.
And beyond that, says Chuck Harris, Commercialisation
Manager for Pipeline Integrity Technology at TDW, the
predictive nature of TDW’s PMI techniques mean they can
reduce the potential for costly field failures when part of a
comprehensive integrity verification programme.
Preliminary results are nearly instant
TDW’s PMI solution includes multiple NDE methods (see The
A-B-Cs of PMI sidebar).
The process begins by establishing an area to inspect,
followed by determination of yield and tensile values,
plus chemical composition and carbon equivalence. The
results are then compared to American Petroleum Institute
specification API 5L, tables 4 and 6, to ascertain the pipe
material grade.
According to Chris Caraway, NDE Operations Manager,
TDW’s process, performed completely in the ditch in about
four hours, means there is “zero destruction to the pipe and
product in the line is never affected. The NDE PMI process
leaves no potential leak path.”
Reporting time is also much shorter than other PMI
methods. Initial findings are almost instantaneous. The
operator often has a draft in-hand before the technicians
leave the field. Normal turnaround for the complete report is
five days. Which is less time than it takes to get a cheek swab
result back from the DNA lab.
PMI: determining the DNA of pipelines
While tracking down relatives and adding leaves to the family
tree can be fun, there is a serious side to it, too. Like when
that cheek swab identifies potentially lifesaving information
about the genes you share with your ancestors.
And in that way, PMI is very much like DNA testing for
pipelines: it is a way to dig deeper than old records and
photographs allow, providing information at the cellular level,
mitigating risk today and in the future, while maintaining
compliance with industry regulations.
References
1.
Visit phmsa.dot.gov for a criteria-based definition of high and moderate
consequence areas.
The A-B-Cs of PMI
TDW’S PMI solution is a step-wise process that includes
these non-destructive techniques:
)
Ultrasonic thickness testing (UTT) uses high
frequency sound energy to verify actual wall
thickness (ATW).
)
AUT B-scanner scans pipes circumferentially to
detect corrosion and other anomalies.
)
Automated ball indention (ABI) uses a sophisticated
algorithm to determine material yield strength based
on a stress strain curve generated by equipment
software.
)
Optical emissions spectrometry (OES) identifies and
determines the concentration of elements as well as
the carbon equivalency value for welding purposes.
)
Magnetic particle testing (MT) uses the application
of a magnetic field to detect the presence of surface
or near-surface discontinuities.
28
World Pipelines
/
JUNE 2015
