Pipeline coating 2013 | conference report
at the end of the pipe in the pipe coating plant, which is followed by the application of a epoxy-bondable band. Lam said the new technology provides pull-off adhesion results of more than 14MPa after 60 days in hot water at 85˚C and more than 2MPa after 50 thermal cycles between -40˚C and room temperature. The fi rst pipeline to use the technology will go into the ground this year, she said. Nicolaj Cherkasov, general director of Russia’s SRC
Coating (HPPC) polyolefi n pipe coating system, which the company claims reduces ‘weld tenting’ and voiding and allows thinner polyolefi n layers to be used without sacrifi cing performance or durability. Lam said while the conventional side extruded
application process for three-layer polyolefi n (3LPE) pipe coatings is popular in all markets today except the US, it can suffer from potential weaknesses in the area above and alongside the longitudinal pipe weld. In particular, high spots in the weld can result in consider- able thinning of the polymer by the compression roller during application. Lam said the company has meas- ured thinning down to half the original application thickness in some cases. Voids can also be formed alongside the weld and the
hoop stresses set up by shrinkage of the polymer topcoat during the water quenching process can exacerbate this problem, extending any voiding between the copolymer adhesive and topcoat, she said. The HPPC system replaces the extruded top coat of 3-6mm thick polyolefi n with a powder coated layer of polyolefi n around 500 microns thick. By applying the topcoat in the powder form, it is possible to precisely follow the contours of the pipe surface around the weld, eliminating all tenting and voiding. “The clearly defi ned weld seam in the coating is evidence of this absence of thinning,” said Lam.
Lam said the HPPC line speed is comparable with
current 3LPO processing lines and can run at up to 5.4 metres per minute on a 36-inch diameter pipe. “We are trying to beat FBE but we are not there yet,” she said. Shawcor has also developed a new pipe end pre- treatment system that is claimed to overcome the challenges of obtaining good adhesion to the 3LPO coating, allowing liquid-fi lled or heat shrinkable fi eld joints to be used with the HPPC system. The process involves plasma fl ame treatment of the polyolefi n surface
Poisk, presented a review of the Asmol petroleum- derived mastic that has been widely used in Russian pipeline protection. Unlike bitumen, Asmol contains high molecular weight functional groups that are said to improve adhesion to the metal substrate. While it is no longer widely used in new pipelines, Cherkasov said it is still used in repairs and at fi eld joints due to its good performance and simplicity of application. “There is no need to heat the pipeline to get good adhesion,” he said. Stopaq Industries FAST director Laurent Grodziski
said the company would soon be offering its two-layer viscoelastic pipe coating technology with the option of an extruded polyethylene or polypropylene protective coating. Stopaq’s FAST technology currently comprises
application of a viscoelastic polyisobtylene (PIB) corrosion prevention layer followed by either a shrink- able polyethylene tape (FAST PE) or a glass reinforced epoxy or polyester (FAST GRE) where additional impact or abrasion resistance is required. It is claimed to provide particularly good resistance to cathodic disbondment. The company provides in-plant and mobile coating plants for the FAST PE and FAST GRE systems and Grodsiski said it had delivered three in the fi nal three months of last year and had three more plant under construction. At the end of last year it also carried out tests at Industrie Polieco-MPB in Italy using the company’s polyolefi n extrusion technology with the Stopaq visco-elastic base layer. It claims the FAST EPE
Left: Latest addition to the Stopaq FAST system applies an extruded polyolefi n protective coat, seen here in development at Industrie Polieco
Figure 2: Effect of surface roughness on maximum fl ow rate on a 145km 24-inch OD subsea gas export line
Source: Jotun May 2013 | PIPELINE COATING 43
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