Rotabolt 1 allthread stud bolts are provided for all Grouted
Tee installations. DNV GL recommend the use of bolt tensioning
in preference to torque tightening as this significantly improves
the accuracy and consistency of bolt loading. Constant monitoring
of cap rotation is carried out to ensure that excessive over
tightening is avoided.
Grouted Tee – repair of illegal hot tap
connections
Illegal hot tapping of pipelines is a global problem that poses a
huge risk to safety, the environment, company reputation and
finance. Grouted Tee technology can be implemented to support
a cut out and replacement operation or a single hot tap repair.
This then removes the requirement for flow reduction during
remediation works, quickly and effectively.
The fitting is installed without the requirement of onsite
welding that eliminates the hazard of hot work operations in
close proximity to a potentially fragile illegal hot tap connection.
Removing the requirement of welding activities on a live pipeline
also eliminates the high risk of potential burn through on thinner
wall pipelines during installation. As the Grouted Tee installation
procedure allows the flow and pressure of the pipeline to be
maintained throughout the installation process, the delivery of the
pipeline product is not compromised.
Cost comparisons between welded split tees and Grouted
Tee connections generally show that overall costs are similar.
Although the physical cost of the Grouted Tee is considerably
more expensive than the welded split tee alternative, the
installation costs are significantly less with the total cost
being less at larger diameters and only slightly more expensive
throughout the lower range. With the increased risk of disrupting
product supply when using a traditional welded fitting, the overall
cost savings, when using the Grouted Tee, are generated through
maintaining product delivery.
Road crossings – heavy wall replacement
alternative
Current pipeline design standards generally require heavy wall
pipe to be used for areas along a pipeline that are exposed to
higher external forces such as road and rail crossings. Traditional
means to replace standard wall with heavy wall pipe is
extremely expensive if the operation requires the pipeline to be
decommissioned. This practice may also be hazardous if using
flow stop and bypass procedures.
In 2013, DNV GL supported a major UK pipeline operator
to design and develop a modified epoxy sleeve to create an
assembly of sleeves covering up to 80 m of 48 in. dia. pipeline.
The aim was to provide a cost-effective and safe means to
produce a protective barrier around the pipeline and transfer
stress via pressure increase throughout the remaining life of the
pipeline over a specified length. The design encompassed a forged
bend and several cold field bends to protect and increase the
integrity of the pipeline over the desired length. Overlapping
sleeve sections ensure the gap between each epoxy shell is
covered to provide complete protection to the pipeline over the
specified length of the road crossing. A section of the covered
pipeline is shown in Figure 5.
Due to the successful completion of the project and the
infinite length of pipeline that can be covered in a road crossing, it
is likely that this new approach will be included in future pipeline
standards revisions as a suitable alternative to replacing thick wall
pipe.
Evolution in motion
Epoxy pipeline technology is completely independent to parent
pipe materials. It has seen major modifications over the last
30 years and will continue to provide solutions to the complex
problems faced by operators in the oil and gas industry. Although
epoxy pipeline technology was originally developed to provide
repairs to pipeline defects it has demonstrated its versatility with
design principles and concepts being adopted for an array of
projects and manipulated to many different uses.
With the economic necessity of maintaining production and
reducing risk ever more prevalent in the oil and gas industry, the
use of epoxy technology will become increasingly important in
the future.
Figure 5.
Epoxy sleeve reinforcement project on a 48 in. dia.
high pressure pipeline.
Figure 4.
Example of an installed Grouted Tee.
84
World Pipelines
/
JANUARY 2015
