Oil and gas pipelines are critical infrastructure that require effective corrosion protection to ensure long-term operational effectiveness. Internally coating pipelines with epoxy provides benefits like increased gas flow capacity, faster drying times, and reduced operational costs from decreased pumping needs. Externally, fusion-bonded epoxy coatings form an electrical barrier against corrosion and have proven effective for onshore and offshore pipelines. Pipeline coating technologies continue to evolve to meet industry needs for transporting oil and gas from more challenging environments.

1. ®
Volume 10 Number 11 - November 2010
Reprinted from

2. Covering the
O
il and gas transmission pipelines are
critical elements of infrastructure in the
transportation of fuel. They supply not
only energy and power to many countries,
but in many cases are key strategic elements in
sustaining economic growth and development. As
such, they are precious resources. Given then that
pipelines generally operate in harsh environments,
there is a powerful argument for providing them
with effective protection to ensure their operational
effectiveness over the medium to long-term.
The capacity, as well as operation and pumping
costs of a gas pipeline, can be adversely affected by
the roughness of the internal surface of the steel pipe
and the build-up of corrosion products. The concept
of internally lining gas pipelines was first developed
in the 1950s. The application of a two-component
epoxy coating to the internal surface of gas pipelines
provided enhanced flow of gas, corrosion protection
in storage, optimum commissioning and reduced
operational costs.
External coating systems have also been
designed to form a barrier between the metal surface
of the pipe and the surrounding environment, Since
its introduction in the 1960s, single-layer fusion
bond epoxy (FBE) has proven its capability as an
external pipe coating and is now the most commonly
used pipeline coating in North America, preventing
the build-up of aggressive corrosion-causing
compounds.
Over the past 40 to 50 years, therefore,
international oil and gas companies have grown
to recognise the many benefits of internally and
externally coating oil and gas pipelines and, indeed, it
has become standard industry practice.
The diversified technology company, 3M,
pioneered the use of both the internal flow coating
and FBE, supplying the former for more than
170 000 km and the latter for more than 135 000 km
of pipeline worldwide.
WORLD’S PIPELINES
Craig Thomas, Corrosion Protection
Products, 3M United Kingdom plc, describes
how pipeline coatings are evolving to meet the
future needs of the oil and gas industry.
– inside and out

3. Increased flow of gas - increased
throughput
Increases in capacity of 14 – 21% and even higher are possible
with internally coated pipelines, according to research carried
out by a number of oil and gas companies.1
Yet it is generally
accepted that even a mere 1% improvement in throughput
provides the financial justification for internal coating.
Data is readily available to illustrate that a reduction in
surface roughness leads to increased flow capacity. One of the
conclusions that can been drawn from a study of a 530 km
section of the GasAtacama Pipeline in South America carried
out by Zamorano (2002) is that the capacity of the coated
section was considerably greater (at high pressure) than the
uncoated section.
Y Charron et al (2005) also 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 concluded that the savings
would be even greater at a higher pressure. It was also cited
that drag reduction techniques for the transportation of gas
“are limited at the present time to the use of pipe internal
coatings.”
Those improvements in capacity are now the norm as
the long and successful working relationships between pipe
coaters and manufacturers have resulted in the ability to create
very high standards of smoothness inside pipelines.
Corrosion protection in storage
The degree of debris cleaned from an uncoated pipeline can
vary depending on a number of factors. Several examples have
been reported, concluding that up to 150 000 kg of debris can
be cleaned from an uncoated pipeline measuring 250 km in
length.
When uncoated pipelines are flooded with sea water, the
extent of corrosion can be considerable. John Grover of BJ
Process & Pipeline Services stated in a 2006 report that an
estimated 157 000 kg of corrosion debris was removed from a
161 km section of 36 in. diameter pipe with a wall thickness of
14.3 mm only three months after total immersion in tropical sea
water. He also said that: “Internal coating should be considered
(for gas pipelines) not just on the merits of flow efficiency, but
also for corrosion protection and ease of cleaning and drying.”2
The design parameters of subsea pipelines can vary
hugely as can the environmental and sea conditions in which
they are laid. Consequently, the provision of other specific
case study data is difficult from the point of view of a pipe
coatings manufacturer. Nevertheless, it is possible to give an
appreciation of the order of magnitude of corrosion debris
that could be formed from a larger (370 km x 48 in. diameter)
thicker-walled (25.4 mm) uncoated offshore pipeline after a
period of six months; it having been fully flooded with sea
water. It can be estimated using the same rates of corrosion
and identical engineering calculations as above, that five to
six times the weight of corrosion products might have to be
removed by pigging due to pre-commissioning.
However, as increasingly stringent regulations governing the
disposal of scale and rust debris into the sea/environment are
Figure 1. 44 in. steel pipe internally coated with 3M Scotchkote
Epoxy Coating EP2306 HF for the Langeled gas pipeline.
Figure 2. 48 in. steel pipe coated internally with 3M Scotchkote
Epoxy Coating EP2306 HF (75) for supply into the Netherlands.
Figure 3. Steel pipe coated with a 3M Scotchkote Internal Flow
Coating, creating a smooth, low friction surface.
November
Reprinted from World Pipelines

4. being applied, it has become industry practice is to blast clean
the pipe and apply the internal flow coating prior to the pipes
leaving storage for transport to the pipeline site.3
This 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.
Faster commissioning (inspection)
Internally coated pipework also dries quickly after hydrostatic
testing, thus providing easier and faster commissioning of the
line. Testing and any robotic inspection procedures are also
greatly simplified by the improved mobility of the equipment
travelling down an internally coated pipe. These points reduce
the risk of unnecessary and costly delays in the budgeted
transmission date and, arguably, justify the cost of internal
coating on this point alone.
Statoil reported in 2005 that it made the decision to apply
an internal epoxy coating - 3M Scotchkote Epoxy Coating
EP2306 HF (formerly Copon EP2306 HF) to the Langeled gas
pipeline in order to increase transport capacity and reduce pig
wear. The company also claimed that the amount of millscale
and corrosion products, which would have required pigging,
was reduced. Statoil also stated that pigging distances of up to
800 km could be feasible, when carefully designed pigs were
used in combination with a smooth internal surface created by
the internal flow coating.
Statoil also reported that internal coating of the line also
allowed the pipeline to dry faster after dewatering, leaving less
free water in the pipeline due to the smooth action of the pigs.
Reduced energy costs in pumping and
compressor stations
Another important factor to which an internal flow coating
can make a significant difference is pumping/compression
costs, which are significantly reduced during the lifetime of the
pipeline. These reduced energy costs can provide a financial
payback within three to five years of service. It may also be
possible to achieve further savings by reducing the number of
compressor stations, or compressor size and capacity.
The Zamorano (2002) study also concluded that fuel
gas costs for the compressor stations alone, which were
situated along the 1200 km length of the GasAtacama Pipeline
(20 in. OD), were 26.9% lower on the coated section than the
uncoated.
Another example has been given by Shell Global Solutions,
which reported in 2005 that it had had positive experiences
with the use of internal flow coatings and the associated
CAPEX savings. The example Shell cited related to a 250
km pipeline. For uncoated pipe with an assumed surface
roughness of 50 µm, a pipe diameter of 26 in. is required,
whereas for a pipe lined with an internal flow coating with a
surface roughness of 10 µm, a 24 in. OD pipe is sufficient.
This represents a potential cost saving of 5% and an implied
CAPEX saving of some 2 - 3% on total pipeline cost. The latest
internal flow coatings, such as those manufactured by 3M,
have a surface roughness of 1 - 3 µm.
The following economical and technical benefits can aso
be achieved:
xx Low capital cost.
xx Reduced commissioning costs.
xx More effective pigging/scraping.
xx Sealed surface – product purity.
xx Diverse pipeline use – easier product switch.
xx Rapid payback.
xx Reduced valve maintenance.
xx Minimal sidewall deposition.
xx Improved flow pattern.
xx Simple application.
In short, solvented, thin-film epoxy flow efficiency coatings
have served pipeline operators very well for several decades.
However, their high volatile organic compound (VOC) content
is increasingly considered environmentally undesirable and
ultimately unsustainable. But the advent of a new generation
of ‘high solids’ (reduced solvent content) and 100% solids flow
coatings - all fully approved to international standards - enables
the environmental impact of internal coating processes to be
minimised without compromising coating performance. Higher
solids coatings have also shown the unexpected benefit of
reducing the surface roughness of internally coated pipe and
thus providing better performance.
Figure 4. Factory application of 3M Scotchkote Fusion-Bonded
Epoxy Coating.
Figure 5. Pipe coated with 3M Scotchkote Fusion-Bonded Epoxy
Coating 206N being transported by rail to site.
November
Reprinted from World Pipelines

5. External protection
Here are some of the features and benefits of fusion-bonded
epoxy coating to protect against external corrosion of the
pipe.
The main ways to protect underground pipelines from
corrosion are external coatings and cathodic protection.
According to J. Alan Kehr, a leading American expert on
pipeline coatings, external pipe coatings are “intended to
form a continuous film of electrical insulating material over
the metallic surface to be protected.4
The function of such
a coating is to isolate the metal from direct contact with the
electrolyte, interposing a high electrical resistance so that
electrochemical reactions cannot occur.”
FBE coating systems are highly effective in the prevention
of under film corrosion; they offer excellent barrier properties.
Kehr states that the oxygen permeability of FBE is less
than 20% that of polyethylene (PE). On the one hand, FBE
is subject to a higher rate of moisture permeability. On the
other, PE carries a much lower moisture transmission rate
than FBE, but at a higher oxygen/chloride rate. But when
FBE and PE are used together, their properties can work in
tandem to create a highly effective barrier.
Single-layer FBE and three-layer polyolefin (3LPO) are
considered to be the most commonly used external pipe
coatings in the world. Use of dual-layer FBE coatings has
also increased in recent years on account of their combined
properties. Three-layer FBE also has its place in the pipe
coating industry portfolio, as it can fulfil a number of
environmental requirements.
Single-layer FBE
Single-layer FBE has proven performance in both onshore
underground and offshore subsea environments. It has
proven to be an effective corrosion-resistant barrier for line
pipe, field joints, fittings and bends. Since its first use in New
Mexico in 1960, FBE coating has remained the external
pipe coating of choice in North America. The benefits of a
single-layer coating system are excellent adhesion to steel;
non-shielding to cathodic protection (CP); good resistance to
biological, insect, termite and root attack; ease of installation;
good abrasion and gouge resistance; and good impact
resistance.
Dual-layer FBE
Since their introduction in 1991, dual-layer powder coatings
have also gained popularity for use with pipelines operating
at a high temperature. A relatively low-cost solution, the
coating is not only non-shielding to CP, but is also resistant
to damage - almost on a level with three-layer polypropylene
(3LPP) and three-layer polyethylene (3LPE).
In 1998, this system was enhanced through the optional
addition of an abrasion-resistant outer (ARO) coating to
provide a tough outer layer when the pipe was to be installed
by means of directional drilling.
Dual-layer FBE offers the excellent performance and
installation characteristics of single-layer FBE, but also
provides superior damage resistance with only a minimal
reduction in flexibility.
Three-layer PE or PP coatings
The 1980s saw the introduction of three-layer PE or PP
coatings in Europe. They comprise (1) a FBE primary coating,
(2) Polyolefin-adhesive or tie-layer and (3) Polyolefin topcoat and
are based on earlier single- and two-layer systems.
The thick layer of polyolefin, which provides a high level of
damage resistance, is deemed to facilitate installation under
conditions of a harsh environment or inexperienced handling in
the factory or on-site. The other benefit of a three-layer system is
its performance under conditions of elevated service temperature;
here the low moisture permeation rate of the polyolefin’s topcoat
is key.
Naturally, there is a trade-off between the increased cost of
the three-layer system and the potential savings from for example
reduced use of graded or imported backfill material.
Conclusion
Both internal and external coatings for pipelines are now standard
practice with the economic benefits well catalogued by thorough
scientific research on a number of different installations.
What is certain is that coatings technology - in many cases
led by 3M - is constantly evolving to provide better protection
as the oil and gas industry is forced to explore and produce
from ever more difficult reserves and demanding environments;
environments that will provide ever more challenges for pipeline
designers, manufacturers and operators. Replacing a corroded
length of pipe may be relatively easy above ground in the Middle
East; at a mile below the Gulf of Mexico it is a different matter
altogether!
References
1. FASOLD, H-G., and WAHLE, H-N., Einsatz neuartiger elektronischer Duck- und
Temperatur-Meßgeräte bei Feldgmessungen in Ferngasnetz, gwf Gas-Erdgas
133/Nr. 3 (1992).
SINGH, G., and SAMDAL, O., ‘Economic Criteria for Internal Coating of Pipelines’,
7th
International Conference on Internal and External Protection of Pipes, London,
England (21 - 23 September 1987).
KUT, S., ‘Liquid Internal and External Pipe Coatings for the Oil and Gas Industry’.
Petrotech 2001 – 4th
International Petroleum Conference, New Delhi, India
(9 - 12 January 2001).
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 - 19 October 2005).
THOMAS, C., ‘The Inside Track’, World Pipelines, August 2006.
THOMAS, C., ‘Subsea Coating Successes’, World Pipelines, April 2007.
2. GROVER, J., ‘Mitigating Threats: Strategies in Managing Offshore Pipelines’, Pipeline
(Dubai) Magazine, October 2006.
GROVER, J. L., ‘The Impact Of Offshore Pipeline Installation And Pre-Commissioning
On Future System Integrity’, OSEA Production Conference, 7 December 2006.
3. The Food and Environment Protection Act (FEPA) 1985.
The Coastal Protection Act (CPA) 1949.
The Petroleum Act 1998.
Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other
Matter, 1972 and 1996.
4. KEHR, J ALAN, RAU MARTIN and SIDDIQUI EMRAN, ‘Fusion-Bonded Epoxy (FBE) and
Dual-Layer FBE Materials Provide Enhanced Performance For Pipeline Installation’,
ASME India Oil Gas Pipeline Conference, New Delhi, India (16 - 18 March 2009).
3M and Scotchkote are trademarks of 3M Company.
November
Reprinted from World Pipelines