Nov 3 2009
High power infrared emitters from Heraeus Noblelight, fitted with newly developed opaque quartz reflectors, are helping to ensure the bonding of a high-tech polypropylene composite coating on pipeline manufactured using an innovative pipeline construction technology. The custom-built shortwave infrared system is pyrometer controlled to ±3ºC and is moved around the pipe to allow the infrared heaters to be located as close as possible to the pipe surface.
Traditionally, pipeline for the oil and gas sector is manufactured in lengths of 40 ft (12m), with typical wall thickness around 15mm. Completed pipelengths are next sent to pipe coating yards and then transported to site where they are butt-welded together.
The new pipeline construction technology, X200, from Pipestream Inc, a portfolio company of Shell Technology Ventures Fund 1, relies on using a thin-walled pipe for fluid containment, with the pipe’s hoop strength being conferred by strips of martensitic steel which are helically wound around the thin-walled pipe, at diameters up to 24 inch. The assembly is then coated with a suitable coating material, such as polyolefin tape. Pipe manufacture, including coating, is a continuous process producing continuous pipe lengths in excess of 450m. The individual manufacturing stages are fitted within standard ISO containers, so that pipe manufacture can be carried out at point of use, allowing faster installation, shorter project lead times and higher pressure ratings. To date 6 inch diameter pipes having been manufactured subjected to pressure, bursting at 300 bar.
The manufacturing process is a three-stage one. First stainless steel is formed and welded to create the inner liner. The martensitic steel strip is then helically wound on and fixed to the liner by an adhesive. Formerly, this adhesive was cured using high power infrared but latest versions of the technology use an adhesive which cures at ambient temperatures. Finally, a polyolefin tape is helically applied, both for insulation and for corrosion protection. This is bonded to the pipe by an adhesive, and the high power infrared heaters are used to heat the pipe before the coating tape with its adhesive is applied. As the coating tape is a thermal insulator, it is not possible to cure the adhesive through the coating. However, one pair of heaters heats the tape itself to maintain flexibility. There are three pairs of high power short wave heaters arranged around the pipe circumference. These are rotated to match the winding speed and they are zone-controlled by pyrometers to provide hold temperatures to ±3ºC to ensure adhesive curing and to avoid bubbling or over-softening of the coating tape.
The newly developed QRC infrared emitters used in this application provide high energy short wave radiation rapidly and responsively. Their new quartz reflective coating has a special nano- and micro-structure which provide the reflector with very high diffusion characteristics to ensure the stability of process parameters, such as temperature and coating homogeneity. The emitters operate at around 2000ºC with a power density of 300 kW/m2, enabling them to provide very large amounts of heat rapidly and efficiently to exactly the point of use.