IBP306_03 Pipeline Coatings & Joint Protection: A Brief History, Conventional Thinking & New Technologies Author: Robert Buchanan 1.

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1 Pipeline Coatings & Joint Protection: A Brief History, Conventional Thinking & New Technologies Author: Robert Buchanan 1 Copyright 2003, Brazilian Petroleum and Gas Institute - IBP This paper was prepared for presentation at the Rio Pipeline Conference & Exposition 2003, held in October, 22-24, Brazil, Rio de Janeiro. This paper was selected for presentation by the Event Technical Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the IBP. Organizers will neither translate nor correct texts received. The material, as presented, does not necessarily reflect any position of the Brazilian Petroleum and Gas Institute, its officers, or members. It s Author s knowledge and approval that this Technical Paper will be published in the Rio Pipeline Conference & Exposition 2003 brochure Abstract Pipelines have been in use since oil was discovered and the need to move it efficiently from the well head to secondary transportation, refinery or market was first realized. Early pipelines were obviously crude, but corrosion was understood as being a problem which resulted in the need for corrosion preventive coatings. As coatings technology developed, pipeline coatings became better and longer lasting but also needed to advance as pipelineoperating conditions became more severe. High performance pipeline coatings, such as the 3-layer polyethylene (3LPE) and, more recently, multi-layer polypropylene (MLPP), have been developed to meet the more demanding applications in today s market. Coatings are generally applied under wellcontrolled factory conditions but weld joint systems need to be applied by contractors under unpredictable field conditions and yet provide performance and quality consistent with plant applied coatings. Polyethylene heat-shrinkable sleeves are the most commonly used corrosion protection system for field joints on 3LPE coated pipelines today due to their compatibility, ease of application, reliability and extensive track record. However, there has been an absence of a more universally accepted field joint solution for MLPP coated pipelines. This paper ultimately describes the evolution and development of the latest generation of heat-shrinkable sleeves for 3LPE plus a breakthrough technology in MLPP field joint coatings that has been tested, specified and successfully used in the field on many global projects by leading engineers and contractors, including in Brazil. Introduction The selection of pipeline coatings over the years has followed development of corrosion protection materials and application technologies. From hot bituminous coatings grannyragged over the ditch in the early years, to epoxy and polymer based materials applied in highly sophisticated coating plants that operate today, the technology has come a long way. Field applied coatings for the weld area have also advanced to meet the performance of the mainline coating and give pipeline owners confidence in having a continuous corrosion 1 Product Manager, Canusa-CPS

2 protection layer. This paper provides some of the history, a chronology of mainline coating development and how today s field joint coatings are keeping pace. A Brief History Pipelines have been in use since oil was discovered in the mid-to-late 1800 s and the need to move it efficiently from well heads to markets was realized. Initially wooden barrels on carriages and rail cars with wooden tanks were used but, eventually, the pipeline was invented and, as happens when any new market opens up, entrepreneurs enter the picture. In this case, the pipeline contractor was born. Initially, pipelines were made of wrought iron and rivets, but that was replaced by more durable steel with welding techniques developed around It was discovered that ferrous metals would corrode and that coatings could stop that process, so oil based coatings, lead, jute and a variety of materials were initially used. Asphalt and coal tar based materials were an advancement in technology, but these products were typically applied over the ditch, took time and varied in quality dependant on the skill of the workers. Taking a look at our company s history, ShawCor s predecessor company started off in the 1930 s as a general contractor that expanded into the pipeline contracting. The corrosion coating technology continued to require over-the-ditch application but, in the 1950 s, the company saw the advantage of pre-coating pipe in a plant, which is now a large segment of ShawCor s business. Historically, mainline and joint coatings have been the challenge for contractors who invariably negotiate with the pipeline owners and specifiers over what to do and how efficiently it can be done. Times change, but some things stay the same. Conventional Thinking We can skip forward a half a century or so from the times when rags, asphalt and coal tar were trucked to the right-of-way and field applied, to the more technologically advanced coatings of today which are applied in state-of-the-art plants under ideal conditions. Figure 1 shows the advancment of coatings over the last 60 years. 2

3 Owners and specifiers have a wide range of choices when deciding what coating to apply to their pipeline and, ultimately, the decision is based on performance, economics, durability and construction limitations to name a few. In the oil & gas industry, plant applied coating products like asphalt and coal tar have been largely replaced. Field or plant applied tape was also popular for a long time, but that has also virtually disappeared in favour of epoxy and polyolefin technologies. These coatings are now some of the best ever. With the perfectly coated pipe delivered to site, this is where joint protection system becomes critical. It is commonly recognized that when the pipe is coated in, probably, an ISO registered plant, the steel surface is perfectly prepared and the coating is applied and tested to be of the utmost quality. Should that then be the expectation on the right-of-way? The reality is that once the contractor takes responsibility to weld the pipe string together and complete the continuous corrosion coating with a field applied system, application efficiency is paramount to reduce cost and increase speed, especially for offshore projects. Therefore, the joint protection system must be engineered with this in mind. Referring back to that earlier figure, the development of coatings has continually moved forward, but where has development of joint protection systems gone? Research of joint protection coatings obviously needs to stay in step with mainline coatings, and has, as seen here in Figure 2. The development of polyethylene cross-linking technologies in the 60 s lead to currently available heat-shrinkable sleeves, which are the most common type of field joint protection on pipelines today. Advances in cross-linking technology moved from the use of chemicals and inconsistent moisture curing processes to the current, more consistent, irradiation crosslinking processes used by the major producers. Initial adhesive technologies for heat-shrinkable sleeves were butyl mastic based, but higher operating temperature pipelines required adhesives that would resist these temperatures better. Also, the development adhesive technologies to create products that not only stick to the pipeline coating and steel cutback, but also offer corrosion protection, was a critical element. Through the 80 s and early 90s, the types of adhesives used for sleeves, were either 3

4 low shear mastic or hard, hot melt based adhesives that were used in conjunction with 2- component liquid epoxy primers. New Technologies Field Joint Coatings Following the mainline model, early joint coatings like asphalt, coal tar and cold applied tape has been largely replaced by commonly available heat-shrinkable sleeves, field applied fusion bonded epoxy (FBE) and, more recently, multi-component liquid applied coatings. The latter two technologies primarily being used on FBE coated pipelines. Relative to heat-shrinkable sleeve technology, in the mid 90 s Canusa developed a hybrid adhesive that had the benefits of mastics, i.e. adhesion at reasonable pre-heat (installation) temperatures, plus shear and peel resistance offered by a hot melt adhesive. As discussed above, another aspect of a high-performance joint protection system is an epoxy primer. This is used to provide primary corrosion protection, as is common for 3-layer coatings. For many years a wet primer system was used, which basically meant that the sleeve would be applied over the joint with the uncured primer acting as a bonding layer for the sleeve to the cutback and mainline coating. This technology had many drawbacks so Canusa also designed a force curable primer to go with the new adhesive technology. These advances in adhesive and epoxy primer technology have been well accepted by the marketplace and the system shown in Figure 3 has proven itself on thousands of kilometers of pipelines, in many Countries around the world. Now we step into the 21 st century, where drilling technologies and exploration of oil and gas reserves are driving deeper. Since these natural resources are flowing at much higher pressures and temperatures than ever before, operators are demanding coating performance at much higher pipeline-operating temperatures, exceeding the limits of many historical coating types. Polypropylene coatings have been proven to withstand pipeline-operating temperatures of over 130 C, plus offer enhanced chemical, mechanical and thermal performance at various thicknesses and densities. Multi-layer polypropylene coatings (MLPP) have become the natural choice on many global projects, both onshore and offshore. 4

5 For many years the benefits of MLPP, over more traditional 3LPE and FBE mainline coatings, has been well known. However, the economics and difficulties associated with installing a field joint protection system that offered equal performance to the MLPP mainline coating has limited the use of this exceptional coating to only a few high performance pipelines. Today, many specifiers and owners are looking at MLPP for the previously mentioned thermal performance, but also for its chemical resistance and mechanical performance. As example, some offshore lay contractors are demanding MLPP rather than 3LPE or FBE since it offers a virtually damage free coating, allowing quicker pipeline laying on expensive lay vessels. Fast, economical and easy-to install field joint protection systems for MLPP-coated pipelines, has been the Achilles Heel of coating selection. Therefore, many companies have been striving to answer this marketplace need, each taking their own path, be it system design, installation technology, service, or a combination of all three. Figure 4 depicts two fundamental field applied systems for polypropylene joint protection. As a manufacturer of coating products used on pipelines, Canusa chose to take the path of developing a finished product. Also, since Canusa was one of the leaders in developing the cross-linked backings and corrosion resistant adhesives used in today s most advanced polyethylene heat-shrinkable sleeve systems, they took the same path with a polypropylene joint protection system. Therefore, the joint protection system developed by Canusa consists of a cross-linked and stretched polypropylene backing coated with a polypropylene adhesive. To ensure compatibility with the mainline coating, both the backing and adhesive were based on the same polypropylene raw materials as used for plant applied MLPP pipeline coatings. The only difference was that additives were formulated into the backing to enable cross-linking and the adhesive was formulated to be able to attain adhesion at reasonable installation temperatures. The challenge with this technology came from the difficulty in being able to cross-link polypropylene polymers, while maintaining their core properties. This achievement was a significant breakthrough in the plastics industry. 5

6 Since heat-shrinkable sleeves need to transition from the coating on each side of the cutback, protect the steel and cover the weld bead, the sleeve also needed to be engineered to accommodate this. This was accomplished by balancing the cross-sectional thicknesses of the adhesive and backing to be able to bridge the transitions. This is a slight departure to the mainline coating design and other joint protection systems approach, as they typically use a thin layer of adhesive and very thick layer of topcoat, reference Figure 5. Fundamental performance of the various approaches are similar, with each providing a joint protection system that closely replicates the performance of the mainline coating. In addition to the polypropylene heat-shrinkable sleeve, the 3-layer joint protection system design required a 2-component liquid epoxy primer which needed to be formulated to replicate the high temperature FBE primer used in the mainline coating. The challenge was to develop a liquid primer that could perform at the elevated pipeline operating temperatures demanded by the marketplace. This was accomplished using the same force-cure technology that was discussed earlier. The complete joint protection system, with the polypropylene heat-shrinkable sleeve and force-cured, high temperature primer, has successfully passed key tests including Adhesion, high temperature Cathodic Disbondment and Hot Water Soak tests. In the research and development project, it quickly became evident that, aside from producing an engineered product, the installation technology needed to be developed in order to provide a complete package that could be successfully field installed. This was done through several months of trials on different pipe diameters, pipe wall thicknesses and coating thicknesses, and by working with suppliers of induction heating equipment. Installation of the system utilizes induction heat to pre-heat the cutback and force-cure the primer. Once the joint is heated, the installation follows typical heat-shrink sleeve installation methods. Spinning off of the development of installation technology, it was determined that, since the joint protection system was a manufactured component and installation was relatively simple, the product could be applied with commonly available equipment, using the pipeline contractor s own crews. Essentially, the installation challenges with field applied raw materials was pre-engineered into the product, much like what occurred when pipeline 6

7 coatings moved off of the right-of-way and into the plant. Figure 6 is a series of photos taken during installation of the polypropylene heat-shrinkable sleeve recently applied on the Guanabara Bay PE 3 pipeline. Conclusion The development of next generation heat-shrinkable sleeves for 3LPE and the new polypropylene heat-shrinkable sleeve for MLPP has taken several years of dedicated research by several polymer chemists, engineers and technicians. Today Canusa s GTS-65, GTS-80 and GTS-HT systems are the most advanced in the industry for 3LPE and FBE coated pipelines, while GTS-PP is the world s first cross-linked polypropylene heat-shrinkable sleeve for MLPP coated pipelines. All told, these products have been specified and applied on thousands of kilometers of pipelines, on projects around the world. 7