Vlad Popovici, Bredero Shaw FJS, Canada, Adam Jackson, Bredero Shaw, Norwayand Peter Jackson, ShawCor, Canada, introduce a new end-to-end thermal insulation solution for pipelines.

Figure 1. The new Thermotite® ULTRATM end-to-end coating system.

New oil and gas exploration and production is moving more and more toward frontier provinces, with probably the most important of them – in terms of current and forecasted

investment - being the offshore deepwater regions around the world. In this context, a noticeable trend is that new upstream offshore projects are being developed in increasingly deeper water and with higher design operating temperatures. Pipeline installation depths over 2500 m and service temperatures over 130 °C are not uncommon nowadays. These increasingly more stringent requirements create in turn a growing need for proactive flow assurance management to ensure that acceptable product flow is maintained in the gathering and

transportation pipeline, that cooldown time is maximised with the risk of wax or hydrate formation reduced. In response, the industry has developed various active and passive approaches to flow assurance management, such as direct electrical heating (DEH) and thermal insulation coatings, respectively.

Until recently, the development of thermal insulation coatings has been focused on four main material groups: epoxies, polyurethanes, polypropylenes and rubbers, which have been applied as solid, blown foam or syntactic foam systems.1 Over time, polyurethane and polypropylene-based coatings have become the most widely used thermal insulation systems for pipelines due to overall performance and cost effectiveness.

InsulatIon InnovatIon

Operators and pipeline design engineers use a wide range of criteria to select the optimum thermal insulation coating system. These can be categorised as: technical performance (such as low thermal conductivity and long-term in-service performance); flexibility of design and application (such as pipe diameter, coating thickness and density, and ease of application); economics and availability; and environmental (such as the recent trend towards mercury-free insulation materials).

The coating selection criterion that is paramount is the availability of an end-to-end thermal insulation coating system, meaning that the same or highly compatible coating systems can be applied on both the pipe and the field joint areas. An end-to-end solution is critical in order to avoid the perception of the field joint being the weak link in the system in terms of parent coating/field joint compatibility issues or lower thermal insulation performance of the field joint coating.

A novel approach to thermal insulationThe most widely used thermal insulation coatings generally have excellent performance, but limitations of existing systems do exist. These include: technical performance issues (for example, hydrostatic pressure limitations, and relatively high thermal conductivity of some systems); design limitations (such as excessively thick coatings leading to subsea stability and buoyancy issues); and

unfavorable coating system economics (such as high cost for average or low insulation long-term performance).2, 3

Bredero Shaw’s experienced R&D team took up the challenge of addressing these by developing a novel end-to-end thermal insulation pipeline coating system. After several years of intensive research and development work, including system optimisation and full-scale qualification trials, Bredero Shaw launched its new Thermotite® ULTRATM thermal insulation system in 2009. This novel system was recognised as such with a Spotlight on New Technology Award at the 2010 Offshore Technology Conference (OTC). The transition from R&D concept to production was reliably realised through an extensive production verification process.

Commercially, Bredero Shaw has already successfully applied 48 mm of Thermotite® ULTRATM thermal insulation coating on line pipe for a 10 km pipeline project in the Gulf of Mexico. Its sister business unit, Bredero Shaw FJS, applied the Thermotite® ULTRA-FJCTM field joint coating system on a spoolbase in the region.

The first pillar of the Thermotite® ULTRATM success story was to the identification and optimisation of materials having inherently better thermal insulation properties than existing thermoplastic pipeline coating solutions. Adapting the well-known insulation properties of styrenic polymers, the Bredero Shaw R&D team developed a multilayer coating system with superior thermal performance, good ductility and excellent impact resistance. The second pillar was the facilitation of Thermotite® ULTRATM application in existing pipe coating facilities. This was accomplished through an innovative re-configuration of existing Bredero Shaw plants, as well as a detailed optimisation of the coating process parameters. Finally, the third pillar in the successful launch of Thermotite® ULTRATM was the development of an end-to-end coating system to address the critical customer concern previously noted. This challenge was addressed by the Bredero Shaw R&D team through the development of a field joint coating system that is perfectly compatible with the mainline coating and offers equivalent long-term technical performance.

A new field joint coating solutionThe new Thermotite® ULTRATM pipe coating system has required the development of a fully compatible field joint, Thermotite® ULTRA-FJCTM. This field joint solution is a combined corrosion protection and thermal insulation coating system based on styrenic thermoplastic materials and comprising three main layers. The first layer, a fusion-bonded epoxy (FBE) layer of minimum 125 μm, provides excellent anti-corrosion protection of the steel pipe. The second layer is a styrenic-based adhesive, Thermotite® ULTRABond, which has a thickness of approximately 150 μm. This layer guarantees the integrity of the coating system by bonding the anti-corrosion layer to the third layer that provides insulation - Thermotite® ULTRAJoint.

The styrenic materials on which the Thermotite® ULTRA-FJCTM field joint coating system is based offer

Figure 2. Heating the chamfers prior to injection moulding.

Reprinted from November world pipelines

unique properties including low thermal conductivity, high impact resistance, long fatigue life, low water absorption and excellent dimensional stability. As such, the system offers significant benefits to the customer, the most important being an end-to-end system with uniform thermal insulation performance over the entire pipeline. Also, the low thermal conductivity of the system enables thermal insulation coatings to be designed with lower thicknesses compared with existing thermoplastic insulation systems, such as those based on polypropylene, for example. In addition, the higher density of the styrenic materials used mitigates potential seabed stability and buoyancy control problems.

The Thermotite® ULTRATM end-to-end system is extremely robust since the field joint coating is integrally fused to the parent line-pipe coating, allowing for any pipeline installation method, including reeling. The system also offers unequaled flexibility for thermal insulation system design engineers, since it has no depth limitations in the solid state. Finally, Thermotite® ULTRATM offers economic benefits as a result of reduced insulation thicknesses translating into lower overall installation costs.

A flexible field joint coating processThe Thermotite® ULTRA-FJCTM field joint system has been designed for application by injection moulding, a proven process used for existing field joint materials such as polypropylene. Process parameters have been optimised for the materials used, but the main process steps have not changed. The innovative field joint coating system is applied by Bredero Shaw FJS, a business unit of ShawCor specialising in field joint and custom coatings.

In a first step, abrasive blasting prepares the steel surface of the field joint area to Sa 2.5 finish. The ends of the factory-applied parent coating are then prepared through abrasion to expose fresh coating material. Induction heating then rapidly raises the steel temperature to 240 ˚C.

After the pipe heating step, a controlled fluid air system automatically applies epoxy powder and Thermotite® ULTRABond adhesive to the pre-heated pipe surface and to the desired dry film thickness within the gel time of the FBE. The parent coating is then checked for contamination and if necessary cleaned.

The cutback chamfers are then heated prior to injection moulding of the Thermotite® ULTRAJoint material to facilitate fusion between the injected material and the parent coating material. Precise control of the heating of the parent coating is accomplished using an IR heating system with a feed back loop.

The injection moulding equipment is then positioned centrally over the joint area and the mould is closed. Visual checking of the seals ensures that no uncontrolled leaking will occur. When the closing sequence is completed, the molten Thermotite® ULTRAJoint material is injected. The injection stage continues until the infill has completely filled the checking gap on top of the mould. As soon as the injection sequence is completed, the mould is cooled and then opened. The mould is removed shortly before moving the pipe down the line in order for a visual examination of the demoulded joint to be made. Finally, water quenching provides additional cooling as the completed field joint is moved forward from the field joint coating station. The field joint is typically applied to provide an 8 mm over-build over the parent coating thickness and a 50 mm overlap either side of the joint.

The Thermotite® ULTRA-FJCTM field joint coating process is highly flexible. It can be used in different configurations, with one or multiple field joint coating stations and can be installed anywhere on-site coating is required, such as at spoolbases and on pipelaying vessels.

ConclusionThe Thermotite® ULTRATM system is an innovative end-to-end thermal insulation solution for offshore pipelines developed by Bredero Shaw that offers significant technical, design, installation and economic benefits to the customers. In addition, the system has been designed to utilise existing coating processes for ease of application and installation.

Future developments of the Thermotite® ULTRATM system will include higher temperature and lower density versions, and solutions designed for other subsea production structures, such as bends spools and jumpers.

References1. JACKSON, A., JACKSON, P., WAN E., HEGDAL, J.P. (2009), ‘A Novel

Thermal Insulation System for Bonded Subsea Single Pipe Wet Insulation Applications’, 18th BHR Conference on Pipeline Protection, Antwerp, Belgium, 4 - 6 November 2009.

2. JACKSON, A., JACKSON, P., WAN E., ØSTBY, G. (2010), ‘A Novel thermal insulation system for bonded single pipes in subsea deep water environments’, AMI Pipe Coating Conference, Vienna, February 2010.

3. JACKSON, P., JACKSON, A. (2010), ‘A Novel Thermal Insulation Coating for Deepwater Subsea Pipelines’, Scandinavian Oil-Gas Magazine, no. 7/8 2010.

Figure 3. Thermotite® ULTRA-FJCTM field joint coating and the injection mould.

Reprinted from November world pipelines