Steel pipelines have evolved significantly over thousands of years from bamboo pipes to modern welded steel pipes. In the 19th century, the first welded steel pipeline was built in London and the first oil pipeline was created in Pennsylvania. Flexible steel pipe was first used during World War 2 under the English Channel and later revolutionized offshore oil transportation. FlexSteel combines steel reinforcement and HDPE plastic to provide a durable, flexible, and corrosion resistant pipe. It has been successfully used for numerous onshore and offshore oil and gas projects globally.

1. NEXTGENERATION
Cindy Trahan,
FlexSteel, USA,
discusses significant
steps in the evolution
of steel pipelines and
presents the latest
developments.
P
ipelines have been in existence globally for thousands of years. Even
before the Roman aqueducts, hollow bamboo pipes were used in
ancient China to convey water. As early as 400 BC, the Chinese used
bamboo pipe to transmit natural gas to light the capital city of Peking.1
Centuries later, in 1815, the first welded steel pipeline was built from old musket barrels;
this pipe system was used to provide coal lamp oil throughout the city of London. The
success of this pipeline created a demand for long metal tubes, the precursors to our modern day
stick pipe.2
Some 50 years later, Samuel Van Syckel revolutionised the way that oil was moved from wellheads to
refineries when he created the first oil pipeline in Pennsylvania, USA.3
Pipeline construction was spurred on by
the extremely high wages that the teamsters charged to haul wagonloads of oil barrels to the point of sale. The
need to transport natural gas and oil over greater distances prompted the development of high strength steel
Figure 1.
Flexsteel’s pipe was
hand placed in an
environmentally
protected wildlife refuge
in the northeastern US;
the company had to wrap
tree trunks with padding
and pull the pipe manually
to keep from scarring
a single tree.
THE

2. pipes. The introduction of welded pipe joints in the 1920s
led to more leak-proof pipelines that could contain greater
pressure.
The first reeled pipeline
The first reeled pipeline was pioneered during World War II
to supply large quantities of fuel to allied armed forces in
Europe. Known as Operation PLUTO (pipe line under the
ocean), the top-secret subsea pipeline was constructed from
flexible steel pipe and run under the English Channel from
England to France. PLUTO was an unprecedented leap in pipe
technology that established reeled pipe as an efficient means
of installation.4
Offshore steel reinforced spoolable pipe
The French Petroleum Institute (IFP) championed flexible
steel pipeline technology in the early 1970s with its patent
for a high pressure, flexible pipe.5
The IFP prototypes laid the
groundwork for the development of flexible subsea flowlines.
Flexible pipelines quickly revolutionised the offshore oil
industry, enabling the exploration and production of a new
frontier, the petroleum reservoirs buried deep beneath
oceans.
Onshore steel reinforced spoolable pipe
Pipeline technology rapidly advanced over the following
decades, with Wellstream International Limited emerging as
significant innovator of deepwater flowlines and risers for the
oil and gas industry. Now a GE company, Wellstream drew on
more than two decades of experience manufacturing steel
reinforced pipe for demanding offshore environments to
pioneer the best possible solution for onshore and shallow
water pipeline applications.
The new product line was called FlexSteel, and it
combined chemically resistant high density polyethylene
(HDPE) plastic with steel reinforcements. Full production of
FlexSteel began in 2004, bringing to market a product that
couples the best features of flexible pipe with the durability
of steel. The FlexSteel business unit was later acquired by a
privately owned firm in Houston, Texas, and now operates
under the name FlexSteel Pipeline Technologies, Inc.
Design standards
The FlexSteel™ pipe design features an extruded polymer
liner, a layer of helically wrapped steel strips and an outer
shield. The smooth HDPE liner and shield provide resistance
to corrosion. The combination of the helically wound steel
strips and HDPE layers result in a strong, flexible pipe product
that has a minimum bend radius of 3 - 5 ft, among the lowest
of any spoolable reinforced pipe. The pipe is connected
using a swaged system of end fittings that are designed,
manufactured and tested to API 15S. The pipe can be spooled
for continuous pipe lengths ranging from 591 ft (for the 8 in.
dia. pipe) up to 6578 ft (for the 2 in. dia. pipe). Longer lengths
mean fewer connections and consequently, faster installation.
Since connections can be points of increased vulnerability
along a pipeline, reducing the number of connections also
reduces the number of potential leak paths.
Material selection
The strength of the FlexSteel pipe structure is provided by
the steel reinforcement, which consists of contra-wound sets
of steel strips applied over the liner. The steel used in the
Figure 3. Up to 6578 ft of continuous steel reinforced pipe can
be spooled onto a single reel.
Figure 2. The extruded polymer liner and shield provide
corrosion resistance.
REPRINTED FROM World Pipelines / JANUARY 2015
Figure 4. Pipe deployment from a barge in Lake Maracaibo,
Venezuela.

3. Figure 5. Corrosion resistance and zero-emissions ensure minimal pipeline disturbance
to the environment. (Photograph courtesy of Carnegie Wave Energy)
reinforcement layer is a widely available commercial grade
with excellent strength in both pressure containment and
axial load bearing capability. An alloy steel grade is available
that provides excellent resistance to sulphide stress cracking
and hydrogen induced cracking.
The corrosion resistant liner and the corrosion resistant
shield are produced from a high density polyethylene
compound with carbon black additions
for resistance to ultraviolet radiation. A
white masterbatch has been developed
for more extreme temperature and UV
exposure in unburied desert applications.
The white pipe has withstood over
10 years of outdoor exposure in a
North American desert and accelerated
weathering tests replicating 20 years in an
Oman desert.
Qualification testing
Qualification testing is conducted on all
flexible steel pipe designs to ensure pipe
integrity:
)) Burst tests verify that the flexible
steel pipe meets design criteria.
)) Axial tension testing provides
practical limits during installation.
)) Collapse pressure tests determine
the maximum water depth for marine
applications.
)) The end connection accelerated life
test uses elevated temperature to
accelerate creep and stress relaxation
of the thermoplastic layers within the
end connection to ensure a leak-tight
connection.
Product success
Within two years of being introduced to
the market, FlexSteel’s steel reinforced
spoolable pipe won the prestigious
“Enbridge International New Pipeline
Technology Award” at the inaugural
International Pipeline Awards held at the
2006 International Pipeline Exposition,
Calgary. This award was presented to
the company who, in the opinion of the
judges, had contributed significantly to
the development of the pipeline industry.
The product gained momentum quickly,
requiring FlexSteel to add a second
manufacturing plant to keep up with the
market demands for production.
The company was also honoured with
the “2013 Plastics Pipe Institute Energy
Piping Systems Division Project of the
Year Award” at the PPI’s Annual Meeting.
The highly competitive award pays tribute to innovative
installations and uses of polyethylene (PE) pipe throughout
the USA. PPI selected FlexSteel for the award because a
project in which 16 900 ft of its newly developed 8 in. dia.
1500 psi pipeline was installed to transport water to a drilling
site in the mountainous terrain of the Marcellus Shale Basin.
The 8 in. steel reinforced polyethylene flexible pipeline was
JANUARY 2015 / REPRINTED FROM World Pipelines
Figure 6. Steel reinforcement can also provide the required weight for negative
buoyancy. (Photograph courtesy of Carnegie Wave Energy).

4. installed in one-third of the time of traditional steel pipe
alternatives and delivered a variety of critical cost-saving
and performance benefits.
More recently, FlexSteel pipe has been selected for use
in Australia’s high profile Carnegie Wave Energy Project.
Supported by the Australian Renewable Energy Agency’s
Emerging Renewables Program, the project converts wave
energy into zero emission electricity and desalinated water.
Steel reinforced spoolable pipe was chosen due to its
durability and corrosion resistance, and because the steel
reinforcement provides the weight for increased on-bottom
stability.
FlexSteel was also the subject of a paper presented at
the 2014 International NACE conference in San Antonio,
Texas.6
The paper documents test research conducted by a
Venezuelan oil company to evaluate FlexSteel materials and
operational performance
during service of multiphase
oil, water and gas flowlines
in the Lake Maracaibo
oilfields. Due to the novelty
of offshore flexible steel
pipe systems in South
America, the customer
mandated that the pipe be
evaluated both in the lab
and during real offshore
operation conditions.
The test programme was
developed per API 17J and
API 17B requirements to
assure the mechanical
integrity of the flexible
pipes. Every three months,
testing was conducted
on both new and aged
samples extracted from the
field. These tests included
mechanical properties tests,
hydrostatic pressure tests,
gas-venting tests, ageing tests and gauge tests. The pipeline
was also subjected to continuous inspection and monitoring
of the gas venting system during service. After three years
of service, no failure or damage was detected in any of the
nine experimental flowlines.
The report findings are consistent with the feedback
that the company has received from its other customers.
The product has proven to maintain integrity and is not
de-rated as often occurs with corroded welded pipelines,
thus reducing operational cost expenditures. Highly
corrosion resistant and more durable than other pipeline
products, FlexSteel combines the best features of all
currently available pipe options to deliver superior lifecycle
performance and value. As a result, FlexSteel’s sales more
than tripled between 2010 and 2012, and the company
continues to expand globally, installing over 8000 km of
pipe in 30 different countries.
References
1. LIU, H.,“Pipeline (Technology)”, http://www.britannica.com/EBchecked/
topic/461356/pipeline/64238/History, published by Encyclopaedia
Britannica.
2. HOWELL, D., “A Brief History of Steel Pipe”, http://www.pipelineequities.
com/A-Brief-History-of-Steel-Pipe.php], August 2010.
3. PEES, S., “Oil History: 1865, The Van Syckel Pipeline”. Petroleum History
Institute, http://www.petroleumhistory.org/OilHistory/pages/
Pipelines/van_syckel.html]
4. “PLUTO, Secret Pipelines of WWII”, American Oil and Gas Historical
Society, Washington, DC, http://aoghs.org/petroleum-in-war/secret-
pipelines/#more-780
5. DAWANS, F., JARRIN, J., LEFEVRE T. and PELISSON, M., “Improved
Thermoplastic Materials for Offshore Flexible Pipes”, Paper presented at
the 1986 Offshore Technology Conference, Houston, Texas, OTC-5231-MS.
6. FERNANDEZ, C., and LOPEZ, C., (March 2014). “Use of Flexible Flowlines
for Offshore Conditions in the Lake Maracaibo Oil/Gas Fields”, Paper
presented at NACE Corrosion 2014 Conference, San Antonio, Texas.
Figure 7. Spoolable pipe deploys quickly along a narrow right of way.
Figure 8. Flexible
steel reinforced pipe
structure.
REPRINTED FROM World Pipelines / JANUARY 2015