BSR supplies first offshore three-layer coating project

Citation

(1999), "BSR supplies first offshore three-layer coating project", Anti-Corrosion Methods and Materials, Vol. 46 No. 2. https://doi.org/10.1108/acmm.1999.12846bab.005

BSR supplies first offshore three-layer coating project

Methods

BSR supplies first offshore three-layer coating project

Keywords BSR, Coatings, Corrosion, Pipelines

British Steel Tubes & Pipes and Ramco Energy plc's new company, British Steel Ramco Pipeline Services Ltd (BSR), has successfully completed its first offshore multi-layer coated pipeline project for Allseas Marine Contractors SA.

This order, from Allseas, was for steel pipelines on the Corvette and Ketch projects in the North Sea operated by Shell UK Exploration and Production (EXPRO) on behalf of Shell/ESSO. It included 27km of 18" diameter submerged arc welded (SAW) line pipe and 37km of 20" SAW pipe carrying natural gas. In addition, there were 27km of 3" and 37km of 4" seamless line pipe for chemical injection.

Shell specified a tough three-layer coating with the outer layer in polypropylene because they required a 40-50 year design life for the pipeline and because it was laid in an area where there is the possibility of impact from trawler beams. "Without a tough coating there is also a risk of damage during handling prior to laying," explains Peter Küppers of Allseas.

The pipe coating supply was completed at the end of last August with load out from Hartlepool port. For this project the smooth outer coat of polypropylene was roughened with the sintered application of granular polypropylene to ensure good grip from the lay vessel tensioners and to avoid slippery surfaces for the riggers who have to handle these pipes offshore (Plate 1).

The new coating plant is in addition to the existing fusion bonded epoxy (FBE) coating on the Hartlepool site. It means BSR can now provide external three layer coatings of either polypropylene or polyethylene as well as internal coatings from the same site.

The three layer-coating facilities can accommodate pipe diameters from 3" up to 26" while the FBE can cope with 2" to 26" externally. The internal coating plant can apply epoxy coatings for pipe diameters from 2" to 24".

The complete three-layer system consists of a primer layer of powder epoxy, applied by electrostatic spray, which establishes good adhesion at the interface with the steel. A second layer of polymer adhesive (modified polyethylene or polypropylene) bonds the outer polyolefin to the epoxy layer and is applied by extrusion. The final layer of polypropylene or polyethylene is also applied by extrusion. This provides effective passive anti-corrosion protection and has considerable resistance to damage in transit, laying and servicing.

Plate 1 Pipe being coated at the new BSR plant in Hartlepool

Polyethylene systems are said to provide protection for pipelines up to 60°C and have an established record for onshore pipelines. Polypropylene systems come in two categories, depending on the service temperature of the pipeline, up to either 80°C or 110°C. Polypropylene is claimed to be tougher than polyethylene and hence gives greater protection against mechanical damage. It is used mainly for elevated temperature linepipe either offshore or onshore.

The BSR coating plant produces a coating performance level to meet the requirements of both German and French standards for polyethylene and polypropylene (DIN 30670, DIN 30678, NFA 49710 and NFA 49711).

For details contact British Steel Tubes & Pipes, Project Pipelines. Tel: +44 (0)1536 402121; Fax: +44 (0)1536 404004; or BSR, British Steel Tubes & Pipes. Tel: +44 (0)1429 527286; Fax: +44 (0)1429 273060.