The pipeline coating market has grown from 120 mln sq. mtrs in 2004 to 190 mln sq. mtrs in 2007 at an annual growth rate of 15% according to Applied Market Information. PE accounts for the majority of the market for polymers (over 350,000 tons), followed by PP and epoxy. Asphalt is still used but generally in more specialised applications such as under impinged concrete. Concrete is used as a coating too for weight in negative buoyancy applications. The challenges for pipeline engineers are the increasingly aggressive contents and the harsher operating conditions for oil and gas. Cathodic protection is limited by the amount of current required which requires coatings. Following are the discussions at the AMI Conference on Pipeline Coating.
Bredero Shaw and Shawcor are leaders in the field of pipe coating. Graded structure coatings were developed in the 1990s and comprise an FBE layer covered by an adhesive layer and a polyolefin: the FBE gives excellent adhesion to steel and the polyolefin provides a moisture barrier. The traditional multilayer PE application process can lead to a tenting effect in the weld region – the company’s new technology overcomes this and the outer layer provides enhanced resistance to damage.
As part of TOTAL’s current research and practice 3-layer PE is used up to operating temperatures of 80 degree C and 3-layer PP is used over 80 degree C and offshore, with heat shrink sleeves for field joints. There have been a lot of problems worldwide with coating disbondment and TOTAL is looking to remedy the situation.
In Brazil, Andre Koebsch of Petrobras has worked with pre-qualification testing (PQT) of FBE coated pipeline. The pipe is checked for areas of disbondment, coating thickness, gouge resistance, hardness, roughness, pull off, impact performance etc.
Polyurethane is used as insulation on pipelines, for example subsea. Dow Hyperlast has new technology to reduce weight by 8% and improve thermal properties by 12.5%. Interface bonding, with the use of primers, can increase pull strength to 10 MPa. In the Northern hemisphere current Borealis Borcoat PE meets the challenges from -50 to +85 degree C. The Southern hemisphere requires a range from -30 to +90 degre C, with outstanding UV and mechanical resistance. The new Borcoat HE3450-H meets these demands.
A new PE adhesive has been developed by LyondellBasell to improve bonding and widen the application window (it can be used in induction coil and flame heating systems). The company also has a top coat resin from multimodal HDPE with high safety margins.
EUPEC has been examining PP insulation coatings and field joints. In water depths up to 500m a system of FBE, adhesive PP, solid PP, foamed PP and solid PP is used. For 3000 meters more layers are required, for example a 7-layer system involving, FBE, adhesive PP, solid PP and syntactic PP (with hollow glass microspheres). Joint systems include injection moulded PP (IMPP).
Arkema has 40 years of experience with oilfield applications of polyamide 11. It has been used as a barrier layer in offshore flexible pipes, as a liner for sour gas, in gas pipelines in Australia for 35 years, in desalination plants, water and wastewater treatment plant pipes. The pipe surface must be prepared and primed and the polyamide layer ranges from 100 microns to several millimetres thickness. Evonik is another supplier to the industry and has looked at materials for rotational sintering, used in pipe lining. It produces polyamide12 and PEEK which are very high performance polymers. PEEK can be used at temperatures up to 300 degree C and has high abrasion and chemical resistance.
Bandera has developed machinery to reduce the use of polymer in pipe coating. Pipes are never completely straight so extra coating is used up where the pipe bends. Sensors are used to detect bending and pipe velocity, leading to automatic adjusting of the spray head position according to pipe bending and linear speed. There also savings to be made in sleeve and wrapping processes.
3M invented fusion-bonded epoxy coatings and the first pipeline was installed in 1960. The company also developed dual-layer technology. FBE performs well in acid, base, salt water and solvents (although alcohol can soften the coating). Nordson has studied the coating process for FBE and improved the efficiency and film consistency with better process control and advanced spray guns.
Field joint coatings are critical to pipeline integrity. ExxonMobil Development has been comparing systems: FBE is the logical choice for mill applied FBE pipes; moulded solid PU can be used with an FBE primer; injection moulded PP, heat shrink sleeves and tapes are used for multilayer systems. Each method has advantages and drawbacks. New technology includes fused PP tape with an FBE primer, wide sheet, and low cure temperature FBE.
Canusa-CPS has outlined factors for choosing a field joint coating system including: performance at the operating temperature; soil stress and environmental conditions; resistance to impact; compatibility with existing coating; ability to withstand construction handling and cost. The company has experience of crosslinked polyolefin heat shrinkable sleeves in a variety of projects.
Bodycote Testing has carried out work for most of the major oil operators, testing the quality of pipe and joint coating, and examining cases of failure. The company has built custom test rigs, including flexural fatigue tests (simulating movement on the ocean floor) and full scale pipe reeling.
Dhatec has looked at pipe storage and transport and protecting the pipe from unnecessary damage. The traditional use of rough pieces of wood and steel to support pipe regularly leads to coating flaws. A new pipe support system has been developed called System 88, adjustable to different pipe sizes. Dhatec has studied this in depth including calculating forces in a stack of pipes.
The Abu Dhabi Company for Onshore Oil Applications (ADCO) has extensive quality control systems in place to reduce failure, particularly at the design and manufacture stages of a new pipeline. The gas producers’ lines need particular attention due to high temperature and pressure requirements. Failure of field joints has been due to water and oxygen diffusing through PE, water saturation of the FBE layer and superficial corrosion of the steel
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