Impact, Weight and Anti-Corrosion Coatings for Pipelines

The pipeline industry is continuing to grow worldwide to provide increased security of energy and water supply, and with hostile environmental conditions in many locations, the pipeline protection market is expanding to meet the requirements. Noru Tsalic, Consultant at Applied Market Information, has valued the pipe coating market at around 5 billion euros in 2009 and predicts expansion to 6.5 billion euros by 2013. Tsalic was speaking at the February 2011 annual AMI conference on Pipeline Coating in Vienna, Austria. The highest demand for coatings is in Asia with 23% market share, followed by Europe at 19%, then NAFTA and the CIS states at 17% each. There are a variety of different types of coatings providing different functions: concrete is the highest value sector at 42%, external anticorrosion at 38%, internal coatings at 11% and thermal insulation at 9%. Gas and oil use most of the coated pipeline, with a small fraction in water distribution. There is a newly developing market for pipelines in carbon capture and storage — the International Energy Agency predicts the need for 43,000 km by around 2030 for 1.44 Gt of carbon dioxide capture per annum.

Europe currently imports 54% of its energy requirements each year, and this will rise to 70% in 2030 as its resources are depleted, according to Denso. This is driving the push to build new pipelines including Nord Stream, OPAL and NEL. Europipe is supplying pipe, Max Streicher GmbH is involved in construction and Denso is carrying out field joint coating. Nord Stream is around 1019km long and will carry gas from Russia to Europe, where the OPAL and NEL pipelines will connect it to the existing network in Central and Western Europe. The basic external coating (by Mulheim Pipe Coating) comprises fusion bonded epoxy (FBE) primer, copolymer adhesive, HDPE and finally a sintered PE rough coat to prevent slipping. Much of this pipe is also being coated with an outer heavy concrete at two sites in Mukran and Kotka by Eupec France. The owners of Nord Stream are Gazprom (51%), Wintershall (15.5%), Eon Ruhrgas (15.5%), Gas Unie (9%) and GDF Suez (9%). Denso is using a 2-tape self-amalgamating system for field joint coating of the OPAL pipeline.

There are three main oil companies in China: SinoPec and China National Petroleum Corporation (CNPC)-PetroChina onshore, and CNOOC offshore. At the end of 2009 PetroChina operated around 29,000km of natural gas pipelines, 13,000km of crude oil pipelines and around 9,000km of oil products pipelines. In the 1950s China constructed pipeline with asphalt coatings, starting in 1958 with the first crude oil pipe in Xinjiang. In the 1980s fusion bonded epoxy (FBE) was introduced and liquid epoxy is now also in use. Chief Engineer Liu Lingli of PetroChina indicated that the contemporary trend is for 3-layer polyethylene (PE) coating on line pipe, and FBE at stations. Ageing pipes that need recoating are generally given a primary coating and wrapped in PE tape. There are more international pipelines now, for example, the Sino-Russia crude oil pipeline, the Sino-Kazakhstan natural gas/crude oil pipeline and the Sino-Burma natural gas/ crude oil pipeline. There are plans to build another 50,000km of pipelines from 2011-2015.

Internal plastic pipe coatings have been in use since the 1940s. Valspar is currently reviewing powder coatings for the oil and gas exploration market, which can extend drill pipe lifetime and improve pumping efficiency by providing a smooth surface. Liquid phenolic coatings offer high temperature and chemical resistance, but contain formaldehyde and organic solvents and release volatiles during cure; they also require several thin layers of coating and are subject to health, safety and environmental restrictions. Fusion bonded epoxy (FBE) is chemical and temperature resistant, has no volatiles and is applied as one thick coat: this is a growing market. The test method used for internal coatings in this study was NACE TM0185-2006, which is autoclave testing under high temperature and pressure, with water, hydrocarbon and gas phases, rapid and slow depressurisation.

Petroleum Development of Oman (PDO) has worked on a new specification for internal liquid epoxy coatings. There is a shortage of FBE coaters in Oman and other issues over project completion and qualification, so PDO undertook a market study including liquid epoxy coating and FBE. The latter needs a higher application temperature but cures faster and is more flexible than liquid coating. Conditions for oil and gas pipes were assumed to be 85C, 50% water cut, 3 bar carbon dioxide and 0.5 bar hydrogen sulfide. A search for coating suppliers worldwide followed by testing of materials (ASTM, NACE and PDO, destructive and non-destructive testing (NDT)), narrowed the field to 6 potential products. Although all coatings tested were epoxy novalac based, there was a wide range of performance and the search for a suitable liquid coating is ongoing.

There is a high performance thermoplastic that is now being used in internal coatings, i.e. polyamide 11 from Arkema. The usual application methods are hot spraying or dipping. The polymer is ten times more flexible than FBE and after 5 years of use in a salt water injection pipe there are no signs of degradation or loss of adhesion. The company has undertaken a study with Cybernetix to develop a robotic system that can undertake internal pipe joint coating. The project sponsors include TOTAL and GDF Suez. The robots are required to blast and clean the surface, apply epoxy primer, heat the pipe and apply PA 11 powder, then cool. This is still under development.

BSR Pipeline Services is a 50:50 joint venture between Tata Steel and Ramco. It provides coating services for Tata Steel Tubes, both internal and external. In one of the latest projects, a new 4-layer polypropylene (PP) coating was applied to a 530m section of a new pipeline in the North Sea, owned by Total E&P and laid by Subsea 7. This system comprises epoxy, adhesive, foamed PP and a topcoat of PP and had to meet a required thermal insulation performance of <6W m²/K. According to Tata Steel Tubes, the foam layer is customised for each project and depends on factors such as water pressure and the required insulation value.

Polyurethane (PU) foam is another thermal insulation material. BASF has conducted trials to predict long-term ageing of glass syntactic PU in deep sea applications, looking at several potential failure modes including thermal degradation, water absorption and hydrolysis. Samples were immersed in sea water at 80°C, 90°C and 102°C, and the changes in tensile strength were monitored up to 25 weeks. Long-term prediction-extrapolation methods have been compared.

Deep water offshore insulation coating has been evaluated by Bredero Shaw, looking at thermal and mechanical performance. The heat loss coefficient (K-value), specific heat capacity and hydrostatic load response are measurable features of this. The requirements of the application depend on a variety of factors such as temperature and water depth. Chemical ageing and water uptake can both be detrimental to insulation. The company has tested its foamed polymer coatings in simulated service tests.

Det Norske Veritas (DNV) develops safety standards and recommended practice (RP) including DNV OS-F101 o
n submarine pipelines. DNV has worked with companies like Statoil (Hydro) to adjust standards to improve quality and reliability in the field, which is particularly useful offshore where inadequate coating of pipes and joints can be very expensive to repair after installation. In 2011 two updates will be issued on Submarine Pipeline Coatings, partly for compliance with ISO 21809:

• DNV RP-F106: Factory Applied External Pipeline Coatings for Corrosion Control
• DNV RP-F102: Pipeline Field Joint Coating and Field Repair of Linepipe Coating

Basell Polyolefine (part of LyondellBasell) has undertaken a 5 year study of an advanced 3-layer polyolefin coating, working with Europipe, Mülheim Pipecoatings, BASF Coatings, Salzgitter/Mannesmann Forschung (SZMF) and Wingas Transport on a loop of the STEGAL (Saxony and Thuringia) pipeline. The line is 314 km long and 800 mm/31 inch in diameter with an operating pressure of 90 bar, and the test loop comprises 95 km. The three materials used for coating were: epoxy (Basepox PE50-1081), adhesive (Lucalen G3510H) and polyolefin (Lupolen 4552D black). In addition a 1 km section was coated with crosslinked polyethylene (PEX). On review at 5 years, the 3-layer coating is in good condition with no evidence of disbonding. The PEX provided additional protection in a harsh environment and offers a higher level of abrasion and crack resistance, and can be used at temperatures down to -60C.

External pipe coatings should form a continuous film layer isolating the pipe from corrosive factors such electrolytes. Cathodic protection is often applied as an additional method and to guard against coating “holidays.” Canusa-CPS has reviewed high strength dielectric coatings and the relevant standards, such as NACE SP 0169 and DOT CFR 192 & CFR 195. There are three common requirements in these documents: that a coating should be a good electrical insulator, well bonded and moisture resistant. The NACE standard states that the coating should be applied so that adequate bonding is obtained, to prevent electrical shielding, which is blocking or diversion of the current and can occur if a coating is not bonded. A polyethylene coating has an insulating effect and can reduce the current needed for cathodic protection.

Sometimes the cathodic protection system causes disbondment between the pipe and coating: Exova is leading testing in this area. Coating adheres by adhesive and cohesive mechanisms: if the adhesive strength is higher than the cohesive then the coating may rupture, which allows the cathodic protection to reach the iron. However, if the adhesive strength is lower then blistering may occur and the current cannot reach the affected area. Cathodic disbondment tests assess the interaction of the pipe protection systems and simulate a coating holiday to qualify performance in service conditions. The most frequent request now is for higher temperature testing as oil temperatures are more commonly reaching 150°C.

Wasco Coatings uses a range of technology to enhance pipe coating efficiency, for example, heavy wall seamless pipes are heated with induction coils to heat soak and stabilise temperatures, to counteract wall thickness variations. There are conflicting requirements in the industry, as with FBE coatings where the Canadian and NACE specifications limit porosity, which is not always compatible with a good cathodic disbondment (CD) test result. Wasco Coatings has trialled new materials that are specifically engineered to have low porosity with good CD test results using epoxy resins that have high functionality combined with lower melt temperatures.

In Europe 3-layer polyolefin coatings are prevalent, but in North America FBE is the market leader. 3M has a new toughened, dual layer FBE system with improved properties even at high filler loadings. It has been tested for impact, flexibility and gouge-resistance at a range of temperatures including -30C. Dow Coating Materials has also been improving the impact properties of FBE to limit damage during pipe handling, by adding toughening agents like core-shell rubber (CSR) and self assembly block copolymers. The coating is a significant proportion of the pipe costs, for example in North America it is around 7-10%, which amounts to US$17-24,000 per kilometre. Directional drilling is one of the applications where dual layer epoxy is preferred: an epoxy primer is covered by an abrasion resistant epoxy coat.

Jotun Powder Coatings conducts R&D into new FBE materials and has two new systems. L.E.C. 20+, shows a larger drop in viscosity, more rapidly than convention FBE at the same pipe temperatures, facilitating coating. As a primer it can be applied at 150-180C compared to 185-210C for standard FBE. The other system, Hot Operating Temperature (HOT) FBE was developed in response to user requirements for coatings for pipes operating at 155°C — 3-layer insulated PP plus HOT FBE has been tested for this range.

Pipeline rupture in high consequence areas (HCA) like San Francisco has highlighted the need for thorough risk assessment and integrity management. External corrosion has been linked to some of these events. Berry Plastics has reviewed the use of coatings in HCAs: in 3-layer PE coatings the FBE layer should be at least 250 microns thick with an overall thickness of at least 3mm. The coating should be qualified by immersion in water at 60°C (based on ISO 21809-3) extended to 120 days, and followed by adhesion testing at 23°C. Berry Plastics also recommends the use of fibre-reinforced girthweld coatings to provide additional mechanical strength.

Due to the success of the 2011 conference, Pipeline Coating 2012 will be held at a larger hotel in Vienna, Austria from 27-29 February 2012.

Dr. Sally Humphreys is Business Development Manager with Applied Market Information Ltd. She can be reached at +44 117 924 9442, email sh@amiplastics.com, www.amiconferences.com.