The increased demand for new oil and gas pipelines over the years has provided great challenges and op-portunities for new and innovative pipeline coating

technologies. Challenges in building new pipelines that have unique requirements have led to several recent devel-opments of advanced pipeline coating solutions.

There are three key drivers behind the increased demand for new oil and gas pipelines: 1) about 1.8 percent yearly growth in world energy demand; 2) about 6.7 percent year-ly depletion in world energy production; and 3) techno-logical developments associated with new reserves in more challenging locations.

Energy demand has forced enhanced recovery and tech-nological advances in new or incremental sources such as frontier gas, deepwater, liquefi ed natural gas (LNG), tight gas, shale gas, oil sands and shale oil. This not only drives new pipeline investment, but also challenges providers of pipeline coatings to address requirements in these new environments and applications that traditional pipeline coating technologies have not encountered. Along with oil and gas pipelines, demands for water-related pipelines con-tribute to the need for advanced coating solutions. Overall, about 2.583 billion sq ft of pipe surface areas will be coated in 2010 worldwide.

Opportunities for Improvement

Over the past 55 years, pipelines have been coated with a wide variety of different materials, such as coal tar or asphalt enamels, cement mortar, liquid epoxies, polyure-thanes, polyolefi n tapes, single or dual-layer fusion-bonded epoxy coatings and two- and three-layer polyolefi n coat-ings, to name a few. Figure 1 shows different pipeline coat-ing systems dominant in different regions of the world. While many of these pipeline coating systems have had varied degrees of success and have served the pipeline in-dustry well, there is still room for improvement.

Fusion-bonded epoxy (FBE) and three-layer polyolefi n (3LPO) — which uses polyethylene (PE) or polypropylene (PP) — are the most widely used external coating systems for newly constructed oil and gas pipelines. FBE has been

more popular in North America and the United Kingdom, while 3LPO coatings dominate the rest of the world’s pipe coating market.

Three-layer polyolefi n coating consists of an FBE primer, a copolymer (PE or PP) adhesive layer and a top coat of PE or PP. Over the past 15 years, several incidents of coating failures have been reported with massive disbondment of 3LPO coatings. Adding to the issue is a lack of consistent coating quality and performance of 3LPO from one applica-tor to another. Disbondment of 3LPO can cause shielding to cathodic protection current and further expose the pipeline to environmentally induced cracking. The observed 3LPO disbondment failures have raised concerns in the industry worldwide about the long-term performance of 3LPO coat-ings, resulting in several initiatives to determine the failure mechanisms and corrective measures.

One of these measures is to implement tougher pipeline coating specifi cations and selecting better coating appli-cators. Simply designing and qualifying a pipeline coat-ing or its applicator to meet the short-term and minimum requirements of current standards and specifi cations may not be suffi cient. An approach that relies more on gen-erating data to provide trends in long-term behavior of the pipe coating system should be taken during coating

30 North American Pipelines | JANUARY/FEBRUARY 2010 napipelines.com

New Challenges and Developments in Pipeline Coatings

By Shiwei William Guan

Figure1: market shares of pipeline coatings per region.

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%N.America S. America Middle East Europe N. Africa Asia CIS

Other PE/PP FBE

For more information go to napipelines.com/info

napipelines.com JANUARY/FEBRUARY 2010 | North American Pipelines 31

Frontier gas is found in remote regions with low tem-peratures and complex drilling surfaces prone to frost heaving. In many cases, the pipeline installation in these remote regions must be done in severe winter conditions. These regions have little or no existing infrastructure to support the construction effort or the ongoing operation of the pipeline.

The nature of the soil and the difficulty of providing reliable power mean that the reliability of impressed current CP systems is less than with more accessible pipelines. There is little or no access to high grade back-fill, making conventional padding an expensive and lo-gistically difficult exercise, and the pipelines crossing them are often subject to severe ground movements as-sociated with freeze-thaw cycles and burial in perma-frost. Such circumstances virtually demand the use of strain-based pipeline design, in which the pipe and the coating must be capable of undergoing ground move-ment-induced strains of greater than 1 percent, and in some cases as much as 4 percent. Such designs highly favor the use of high strength steels such as X80, X100 and X120 steels.

High-strength steel allows the reduction of pipe wall thickness, which signifi cantly reduces the costs of pipe materials and transportation. However, applying a coat-ing to a high-strength steel pipe is a great challenge. A coating should withstand the extremely cold tempera-tures and retain the fl exibility needed to protect the

selection and testing. Better surface preparation and coat-ing process control should be implemented to ensure the long-term performance of pipeline coating systems.

Another example for improving existing pipeline coat-ings is to reduce the volatile organic compounds (VOC) and to eliminate the use of heavy metals. Adopting the low solvent or non-solvent coatings often require in-creased capital investment for new application equip-ment, enhanced surface preparation requirements for better wetting and fl ow, and more technical experience and training on application. End-users have to pay ex-tra initially to compensate for the additional costs, com-pared with conventional solvent-based systems.

Fortunately, in some applications, the overall project costs can still be maintained. For instance, traditionally, the most common internal coating for gas fl ow effi ciency application is a solvent-based epoxy coating with a solids content of 60 percent. A new 100 percent solids epoxy product, SureFlo SF, was introduced to the industry in 2007 (Figure 2). The benefi ts of SureFlo SF reach beyond meeting the obligations of health, safety and environmental standards.

Compared with the bare steel and the conventional sol-vent-based coating, SureFlo SF provides a pipe surface that is over 50 percent smoother, with surface roughness reduced from 20 to 35 µm (bare steel) or 10 to 15 µm (solvent-based coating) down to 1 to 4 µm. This signifi cantly reduces tur-bulence and allows natural gas to fl ow more effi ciently. As a result, 10 to 20 percent of pipeline operating cost savings can be achieved through the use of SureFlo SF during the pipeline design life, a very small portion of which can cover the initial additional costs associated with the new product.

Other additional benefi ts include: reduced incidents of potential coating defects due to solvent-related applica-tion and cure problems; a glossy appearance that helps visual inspection; and extra thickness, which produces a tighter polymeric metrix in the cured coating for more corrosion protection.

New Challenges, New Solutions

New pipelines built in terrains, such as rocky soil, moun-tains, steep slopes, rivers and roads, with wet, frozen or silty/clay trench materials, present new challenges for coat-ings providers, especially where the construction weather is extremely cold.

Figure 2: SureFlo SF, a 100 percent solids liquid

epoxy lining for natural gas fl ow effi ciency.

pipes. It should also have good indentation and impact resistance at temperatures down to minus 58 F.

In addition, preheating during conventional FBE/3LPO coating processes will signifi cantly affect the properties of the high-strength steel, causing the steel tensile yield strength to increase, but the elongation at yield to decrease, which could invalidate the strain-based design. It is therefore recommended that high-strength steel used for strain-based pipeline design avoid exposure to temperatures above 392 F. This restriction prohibits the use of conventional FBE coating systems that require the pipe to be heated at 446 to 482 F to give optimal performance and has prompted the development of an FBE standalone coating or an FBE primer for 3LPO systems capable of being applied at temperatures as low as 356 F.

There is a tendency in the industry to construct much larger diameter, raised welded pipelines. Current pipe weld-ing techniques produce welds that protrude up from the external surface. With the conventional 3LPO side-wrap extrusion application, protruding weld seams could cause the formation of “tenting,” where voids, separation of coat-ing layers or discontinuities develop around the weld neck. Accompanying with the tenting effect is a signifi cant re-duction of the coating thickness across the top of the weld compared with the coating on the body of the pipe.

In extreme cases, such a coating thickness reduction could be as high as 100 percent. To ensure adequate coating thicknesses for pipeline protection, most of today’s inter-national 3LPO coating specifi cations allow only zero to 10 percent of the coating thickness reduction over weld seams. This requirement creates a challenge to conventional 3LPO applications, especially on spiral welded pipes where the coating thickness has to be increased signifi cantly, resulting in decreased production output, increased coating and ap-plication costs, and the potential introduction of seriously high residual stress in the polyolefi n layer.

Figure 3 shows a new high-performance composite coat-ing (HPCC), which is used for arctic construction of a 36-in. pipeline with X100 and X120 steel in northern Alberta, Canada. The all-powder components of the multi-layer polyethylene coating and its unique coating application method provided excellent conformity to raised welds and achieved a uniform coating thickness coverage along the weld seams. The new coating with an FBE primer applied at low application temperatures down to 374 F has been used

in several critical high-strength, strain-based design pipe-line projects in North America.

As new and larger diameter pipelines are built in remote areas where tough terrains and climates are often the case, pipeline integrity for durations well above the nominal 25 to 30 years of service becomes an important consideration. Corrosion protection has normally been the focus of the pipeline integrity effort, but mechanical protection also needs to be addressed in order to ensure the integrity of the corrosion protection.

Mechanical protection methods commonly used world-wide are sand bedding and padding, mechanical bedding and padding, rock shield materials and extra thick anti-cor-rosion coatings. All of them have limitations. For example, sand bedding and padding is not good with frozen material and in extreme cold conditions. It becomes impractical for steep slopes and river and road crossings.

Since 1984, Rock Jacket — a bendable, factory-applied reinforced concrete pipe coating — has provided a unique mechanical protection to coated pipes during the entire pipeline transportation, installation and operation life-cycle. It can be buried directly in blasted-out rock trench-es without the use of other expensive backfi ll materials, providing design and installation fl exibility in any type of terrain, trench material and climate without using any additional manpower or equipment. It has the lowest total installed cost and installation time among all mechanical protection systems and the lowest impact on the pipeline right of way and the surrounding environment during installation and lifecycle. Over the last 15 years, Bredero Shaw has completed more than 250 Rock Jacket projects.

Rock Jacket has traditionally only been available in very few fi xed factories in North America and Australia and for pipes smaller than 30 in. Advances have recently made the product available for pipe diameters up to 36 in., and in some cases 48 in., through a unique portable plant opera-tion (Figure 4). The plants can be mobilized in a short pe-riod of time to anywhere worldwide. The newly announced $12 billion PNG LNG project operated by Esso Highlands Ltd. in Papua, New Guinea, has approved the new Mobi-lized Rock Jacket technology for the onshore section of the 560-mile pipeline of predominantly 32 and 34-in. pipes.

Heavy oil production has presented several challenges to pipeline coatings. Pipes insulated thermally with rigid polyurethane foams have been successfully used in North

32 North American Pipelines | JANUARY/FEBRUARY 2010 napipelines.com

Figure 3: HPCC coating used for arctic construction

of a 36-in. pipeline with X100 and X120 steel.

Figure 4: a 32-in. pipe protected with

Rock Jacket at one mobile facility.

America for service temperatures of up to 185 F. However, underground pipeline designs for the heavy oil or bitumen market now operate at temperatures in the range of 248 to 302 F, and aboveground pipelines can be operated at much higher temperatures, demanding thermal insulation at higher temperatures.

Figure 5 illustrates several pipeline coatings selected by the industry to protect a range of pipelines, from fl ow lines and gathering lines connecting to the wellhead to large di-ameter transmission pipelines bringing processed oil and gas to the market. These products include the traditional anti-corrosion coatings such as FBE and Yellow Jacket — a two-layer polyethylene coating for small diameter pipes — the Rock Jacket product, as well as the thermal insulation product line, to which two new high-temperature insulation products, Insul-8 HT and Insul-8 AG, have been added.

Insul-8 HT is a sprayed-on polyurethane foam coating developed for external protection of buried and above-ground pipeline for operating temperatures up to 302 F. Insul-8 AG is a newly developed pre-insulated pipe insula-tion system used for aboveground thermal pipelines for operating temperatures up to 1,202 F, using Aspen Aero-gel’s Pyrogel insulation material protected by an outer layer aluminum sheath.

Offshore pipelines in deepwater and ultra deepwater appli-cations demand new pipeline coatings and particularly new thermal insulation products for fl ow assurance. The most commonly used thermal insulation materials in subsea pipe-lines are polyurethanes and polypropylenes. Since the mid-1990s the average length of tie-backs has steadily increased, and line burial and electrically heated systems have become more common. In these cases, the main workhorse has been polypropylenes.

Very recently a new revolutionary subsea thermal in-sulation system, Thermotite Ultra, has been introduced to deliver optimal performance in any depth of water for operating temperatures up to 257 F. The new prod-uct features specially designed styrenic polymer blends and alloys. Compared to polypropylene systems, Ther-motite Ultra offers improved insulation properties at a reduced insulation layer thickness, extending cool-down period and improving seabed stability in fl owlines. It also contains no glass microspheres, which are incorporated within polyurethane and polypropylene insulation to re-sist the external hydrostatic pressure of the pipes, there-by simplifying production processing and eliminating the risk of decreased thermal performance due to glass

breakage. Figure 6 shows the cutback section of a pipe protected with Thermotite Ultra.

Water pipeline coatings are also facing new challenges be-cause of oil and gas pipelines. Oil sands deposits must be strip-mined or made to fl ow into producing wells using in-situ techniques that reduce the oil’s viscosity using steam and/or solvents. These processes use a great deal of water and require new water pipeline constructions in tough en-vironments. When most design engineers in North America are using 50 years as their benchmark for desired water pipe-line design life, the current industry standards for water and

wastewater are weak or undefi ned to secure the achievement of the 50 to 100 years of design life target. Therefore, the interested parties are currently working together to develop tougher qualifi cation testing protocols and imply tougher performance and application requirements on protective coatings. One of the examples is the Southern Nevada Water Authority, which has recently formed a program to qualify polyurethane and epoxy coatings for its proposed Groundwa-ter Development Pipeline Project — the largest water pipeline project ever in U.S. history. The qualifi cation program has set up many tough performance requirements with which some of commodity coating products may not be able to meet. It is expected that new or improved pipeline coatings will also be introduced to the water pipeline sector.

Joint Efforts to Meet Demands

New pipeline coating technology requirements are driven by: construction in frontier environments; new develop-ments in steel technology; pipe laying in deeper environ-ments; higher operating temperatures; concern for the en-vironment; tighter regulation, specifi cation and legislation; pipelines carrying increasingly aggressive materials, under harsher conditions, through more diffi cult environments; and customers increasingly interested in cost reduction.

These requirements have provided great challenges and opportunities for new and innovative pipeline coating technologies in both oil and gas and non-oil and gas appli-cations. To meet these challenges and requirements is not an easy task, but has been and will be possible with the joint efforts of all interested parties.

Shiwei William Guan is marketing and technology manager at

Bredero Shaw, based in Toronto.

napipelines.com JANUARY/FEBRUARY 2010 | North American Pipelines 33

Figure 5: pipeline coating products selected by the oil sands

industry including new high-temperature insulation products.

Figure 6: cutback section of a pipe protected with Thermotite Ultra.