'Hyperlast' coats Amoco Arkwright oil production line

Citation

(1998), "'Hyperlast' coats Amoco Arkwright oil production line", Anti-Corrosion Methods and Materials, Vol. 45 No. 2. https://doi.org/10.1108/acmm.1998.12845bab.003

'Hyperlast' coats Amoco Arkwright oil production line

Methods

"Hyperlast" coats Amoco Arkwright oil production line

Polyurethanes from Hyperlast Limited were selected from a range of options for corrosion protection and insulation of an 11-km pipeline carrying hot oil from the Amoco Arkwright development ­ the pipe lengths are coated in "Hyperlast" Syntactic, over a "Hyperlast" primer, and the joints are protected by a special "Hyperlast" field-joint formulation. The project was planned in 1995 and the line was laid in summer 1996. Oil began flowing down the line for the first time in the following November, a full two weeks ahead of schedule and the entire project came in under budget.

The Arkwright field is 150 miles (240kms) east of Aberdeen and the hot oil production line, together with others for water, gases and umbilicals, runs at a depth of 95m to the Arbroath platform. For stability and security, the entire group of pipelines has been buried in a trench and rock-dumped for protection. The oil is modified and treated with a wax-point depressant at the Arbroath platform before being piped via the Fortes Field to shore at Cruden Bay.

Inspecting engineers, Interspec Consultants Limited, acted for Amoco as quality consultants during the project, their senior consultant Clement G. Wilkinson explains, "Oil enters the line at 113°C and in order to prevent the oil from reaching !Cloud Point! and solidifying, the temperature of the oil had to be above 45°C when it reached the Arbroath platform. In order to achieve this we made a thorough examination of several combinations of corrosion protection and insulation materials. These included FBE, EPDM and multi-layered polypropylene, combinations of FBE and polypropylene foam or polyurethane and pipe-in-pipe construction with polyurethane or polypropylene filling.

"After looking at all aspects, from material supply and coating methods through to performance records and costs, we were convinced that the best material was polyurethane and the best polyurethane on offer was 'Hyperlast' Syntactic over a 'Hyperlast' polyurethane primer. The combination offers both corrosion protection and insulation and Hyperlast's materials have a strong track record of reliability in the field. This is backed by impressive long-term tests at elevated temperatures, with extremely encouraging results.

"It is because we invested our time at the outset of the project that we were able to bring it to such a successful conclusion. The preparatory work included research at Heriot Watt University, where we established optimum physical conditions for coating the field joints. From this we were able to establish a precise specification for the field joint coaters", adds Clement.

The research indicated best results would be obtained if the "Hyperlast" Syntactic coating was moulded over "Hyperlast" polyurethane primer at a higher temperature than had been used previously. Interspec continued as quality assurance managers until the project was completed. This included advising on the choice of coater and being present at the coating operation. British Pipe Coaters Limited in Leith was chosen because it offered the necessary modified moulding and injection equipment, developed to ensure consistent product quality and thickness, and has extensive experience of this type of work.

The oil production line was made using 8.625in outside diameter steel pipes manufactured by British Steel Hartlepool using the high frequency induction welding process. After priming, a 58mm coat of "Hyperlast" Syntactic was moulded on, to achieve a U value of 2.5 W/m2/°K. Every coated pipe was tested for cured hardness at five or more points along a helical line. The specified minimum hardness required was 88 Shore A.

When the pipeline was laid in August 1996, from the lay barge "Lorelay" operated by Allseas Engineering BV, Interspec personnel monitored the field joint coating. This was carried out by a team from Pipeline Induction Heating Limited (PIH) on contract to Allseas. The bare steel joints were heated to 60°C and blast cleaned to Sa 21/2, then re-heated to 90°C, primed and immediately the mould was fitted and filled with a special field-joint formulation of "Hyperlast" polyurethane. "The technique worked very well", says Clement Wilkinson, "the lay barge had never had a job go so successfully".

Richard Beynon, project engineer offshore Pipelines at Amoco, comments: "This project ran smoothly and is delivering the required performance in the field because of thorough preparation, careful supervision and the selection of quality materials such as 'Hyperlast' Syntactic polyurethane".

Details from Hyperlast Limited. Tel: +44 (0) 1663 746518; Fax: +44 (0) 1663 446605.