1. protecting pipelines
REPRINTED FROM World Pipelines AUGUST 2006 www.worldpipelines.com
T
he application of a two component, solvent-based
epoxy coating to the internal surface of gas pipe-
lines was first carried out in the 1950s. No review
of internal flow coatings would be complete with-
out highlighting the specific benefits of this type
of pipe coating, also known as a flow efficiency or
flow enhancement coating, based on the experience of a
coatings manufacturer that has supplied product for over
140 000 km of lined pipe worldwide during a period span-
ning more than 45 years.
The operation and pumping costs of a gas pipeline are
significant and the capacity of gas delivered by the pipe-
line depends largely on the design parameters of diameter
and length, both key factors in pipeline design.
In recognising these factors, the concept of internally
lining gas pipelines was developed, providing enhanced
flow and therefore reduced operational costs.
International oil and gas companies such as Shell, BP,
Exxon, Total, Transco, Statoil, Reliance, and CNPC have
now recognised the many benefits of internally coating gas
pipelines, which has become industry practice. For this
application, Copon EP2306 HF was developed by Copon
Pipelinings, E Wood Ltd, a pioneer of internal flow coating
technology.
The key benefits of internally coating a gas pipeline
are:
Enhanced flow of gas.
Corrosion protection in storage.
Optimum commissioning.
Reduced operational costs.
Increased flow of gas/throughput
Oil and gas companies have identified that increases in
capacity of 10 - 20% and even higher are possible with
internally coated pipelines. It is generally accepted that
even a 1% improvement in throughput justifies internal
coating from a cost stand point.
Data is available to illustrate that a reduction in sur-
face roughness leading to increased flow capacity is read-
ily attainable.
One of the conclusions that can be drawn from a
study carried out by Zamorano (2002), is that capacity of
the coated section of the GasAtacama pipeline in South
America covering a distance of 530 km was considerably
greater (at high pressure) than the uncoated section.
Y Charron et al (2005) drew attention to the fact that
“the use of relatively smooth (internal pipe) coatings
provides a considerable saving in capital and operating
costs compared to relatively rough coatings” and that the
savings would be even greater at a higher pressure. It was
also cited that drag reduction techniques for the transpor-
tation of gas “are limited at the present time to the use of
pipe internal coatings” (Figure 1).
Corrosion protection in storage
Marine regulations now prohibit the disposal during com-
missioning of millscale and rust debris into the sea or
environment.
Industry practice is to blast clean the pipe and apply
the internal flow coating. This also prevents rust from
reforming, thus eliminating the need for additional pre-
commissioning work, which can be very substantial in
terms of time and cost, particularly for pipes stored in a
marine environment.
It has been reported that up to 150 000 kg of debris
can be cleaned from an uncoated pipeline, which meas-
ures 250 km in length (Figure 2).
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Figure 1. Large diameter steel pipe coated with Copon
EP2306 HF showing a smooth, low-friction internal surface.
The inside trackCraig Thomas, Copon Pipelinings, E Wood Ltd, UK,
discusses how internal flow coatings can
increase throughput in gas pipelines.

2. protecting pipelines
REPRINTED FROM World Pipelines AUGUST 2006 www.worldpipelines.com
Commissioning and inspection
The use of an internal flow coating provides for easier
and faster commissioning of the pipeline after laying, with
more rapid drying after hydrostatic testing.
Uncoated pipe contains many tons of millscale and
rust, which is costly and time consuming to remove (Figure
2). By reducing the occurrence of delays in the budgeted
transmission date, the cost of internal coating can more
than pay for itself on this point alone.
The light reflecting properties of internal coatings
ensure that any pipe wall imperfections will be clearly vis-
ible after inspection with a bright light.
Testing and any robotic inspection procedures are
greatly simplified by improving the mobility of equipment
travelling down the internally coated pipe.
Statoil reported in 2005 that it made the decision to
apply an internal epoxy coating (Copon EP2306 HF) to the
Langeled gas pipeline in order to increase
transport capacity and reduce pig wear,
claiming that the amount of millscale and
corrosion products was reduced. In the
absence of an internal lining, extra pigging
would have been required.
Statoil also stated that pigging dis-
tances of up to 800 km could be feasible,
when carefully designed pigs were used in
combination with a smooth internal sur-
face created by the internal flow coating.
Furthermore,Statoil reported that exam-
ination of the existing methods of drying the
pipeline after dewatering had created large
scale uncertainty as regards the project
schedule, which prompted further research
into pipeline drying. “Internal coating of
the line was also beneficial in this regard,
l e a v i n g
less free water in the pipeline due to the smooth swab-
bing action of the pigs”.
Natural gas pipelines immersed in the North Sea, for
example, may be filled with sea water for a year and the
internal flow coating is required to perform under these
pre-service conditions. The corrosion protection character-
istics of the internal flow coating are therefore extremely
important in these circumstances.
Pumping and compressor stations
Analysis shows that, by applying an internal flow coat-
ing, pumping and compression costs can be significantly
reduced during the lifetime of the pipeline.
It may also be possible to achieve further savings by
reducing the number of compressor stations, or size and
compressor capacity.
The Zamorano (2002) study also concluded that
fuel gas costs for the compressor sta-
tions alone, which were situated along
the 1200 km length (20 in. OD) of
the GasAtacama pipeline were 26.9%
lower on the coated section than the
uncoated.
Shell Global Solutions reported in
2005 that Shell had had positive expe-
riences with the use of internal flow
coatings and the associated CAPEX
savings. The example which was cited
related to a 250 km pipeline required
to transport 300 million ft3
/d at an
inlet pressure of 70 bar and a mini-
mum delivery pressure of 20 bar. For
uncoated pipe with an assumed sur-
face roughness of 50 µm, a pipe of
26 in. OD is required, whereas with
an internal flow coating with a surface
roughness of 10 µm, a 24 in. OD pipe
is sufficient, representing a potential
cost saving of 5% and an implied
CAPEX saving of some 2 - 3% on total
pipeline cost.
The following benefits can also
be achieved:
Low capital cost.
Reduced commissioning
costs.
More effective pigging/
scraping.
Sealed surface - product
purity.
Diverse pipeline use -
easier product switch.
Rapid payback.
Reduced valve mainte-
nance.
Minimal sidewall deposi-
tion.
Improved flow pattern.
Specification
Specifications for the internal lin-
ing of gas transmission pipelines vary
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Figure 2. Uncoated steel pipe contain-
ing a substantial amount
of millscale and
rust debris.
Figure 3. 44 in. diameter steel pipe internally
coated with Copon EP2306 HF for the Langeled gas
pipeline.

3. protecting pipelines
REPRINTED FROM World Pipelines AUGUST 2006 www.worldpipelines.com
depending
on the authority
and the country, but are mainly based on the same essen-
tial principles.
A typical high performance test procedure is laid down
by British Gas, API and more recently ISO. This includes
mechanical coating requirements, such as flexibility, impact
and a high level of adhesion. Another requirement is
resistance to salt spray, humidity, acid condensate, dis-
tilled water, triethylene, glycol, lubricating oil, aliphatic and
aromatic hydrocarbons, methyl alcohol and gas odourising
agents.
The test procedure was conceived to simulate service
conditions in order to ensure the use of the optimum inter-
nal flow coating.
International practice is to specify a two component,
solvent-based epoxy applied to 75 microns dft in a single
coat. The internal flow coating must be fully approved to
API RP 5L2 and ISO 15741 supported by independent
testing. Copon EP2306 HF fully meets these specifica-
tions.
Environmental concerns are taken into account. These
can be divided into two broad areas:
Health and safety requirements. These can normally
be met through appropriate precautions and good
practice.
Requirement to reduce solvent emissions. There is
now increasing pressure on pipe coaters in some loca-
tions to reduce solvent emissions.
Advances in internal flow coating
technology
Higher solids internal pipe coatings
Higher solids coatings are pipe coatings with reduced
solvent content, which of course reduces the level of
solvent emission. These are now economically viable and
available.
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Solvent-free internal
pipe coatings
The natural progression
is the development
and use of solvent-
free coatings.
In 2001, it was
reported that these
would have to be
formulated to give
the low film thick-
ness required and
appropriate curing con-
ditions, and so would
not necessarily meet the
requirements of widely used
specifications, as then written.
Solvent-free internal flow coat-
ings for gas pipelines are now avail-
able and have overcome the technical issues
raised in the early stages of development, though
an inhibiting factor currently is the higher cost per micron
applied, due to the basic cost of the newer technology
resins used.
However, with substantial increase in demand, it is
anticipated that the cost differential between solvent-
based and solvent-free coatings will be reduced. Any
increased coating cost should also be balanced against
the high expenditure called for if incinerators or other anti-
solvent emission measures have to be installed. Copon
Pipelinings, E Wood Ltd, has developed both 75% and
100% solids internal flow coating formulatons, approved
to API RP 5L2. These can be readily applied in accordance
with flow coating specifications of today.
Conclusion
Copon EP2306 HF has been applied to tens of thou-
sands of kilometres of gas pipelines worldwide. Projects
include the Langeled gas pipeline (Norway), the longest
subsea pipeline in the world; the West-East gas pipeline
(China); the Balgzand-to-Bacton line (The Netherlands); the
Bluestream Project (Turkey); the Sakhalin II gas pipeline
(Russia); the Salalah gasline (Oman); and the Fujairah-
Al-Ain gas pipeline (UAE). Copon EP2306 HF has become
virutally synonymous with ‘internal pipe coating’ and was
pleased to receive the Queen’s Awards for Innovation
2006 in recognition of its research activities into new pipe
lining technology.
BibliographyCHARRON, Y., DUVAL, S., MELOT, D., SHAW, S., and ALARY, V., Designing
for Internally Coated Pipelines, 16th
International Conference on
Pipeline Protection, Paphos, Cyprus, 2 - 4th
November 2005.
FALK, C., and MARIBU, J., Extensive Sub-sea Commissioning, Pigging pose
Challenges, Oil & Gas Journal, 21st
November 2005.
FOGG, G. A., and MORSE J., Development of a New Solvent-Free Flow
Efficiency Coating for Natural Gas Pipelines, Rio Pipeline 2005
Conference & Exposition, Rio de Janeiro, Brazil, 17 - 19th
October
2005.
KUT, S., Liquid Internal and External Pipe Coatings for the Oil and Gas
Industry, Petrotech 2001 - 4th International Petroleum Conference,
New Delhi, India, 9 - 12th
January 2001.
Figure 4. 48 in. diameter, thick-walled steel pipe
coated with Copon EP2306 HF for a subsea
gas pipeline in the Middle East.