In recent years, there has been unprecedented interest shown in the Arctic region by the industry, as it has become increasingly accessible for oil and gas exploration, shipping, and tourism. The decrease in ice extent in the Arctic has renewed the interest in the Northern Sea route, necessitating further research to evaluate the adequacy of the equipment and appliances used on vessels traversing in polar waters. In the oil and gas industry, exploration and production vessels and platforms are highly dependent on the piping facilities for rendering their intended function, and therefore, flow assurance is extremely crucial. If the winterization of pipes is not done properly, this could lead to massive cost overruns due to unplanned production shutdowns or even worse, accidents. A temperature drop between the different areas of the production facilities will change the thermodynamic properties of the fluids, and could cause the processing of the crude oil to become inefficient.
The introduction of the Polar Code by the International Maritime Organization (IMO) attempts to mitigate some of the risks endangering the vessels in polar waters. The Polar Code is scheduled to take effect on 01.01.2017, and applies to all vessels traversing in polar waters. The Polar Code requires that all machinery installations and associated equipment required for the safe operation of ships shall be protected against the effect of freezing and increased viscosity of liquids, and that working liquids shall be maintained in a viscosity range that ensures the operation of the machinery. To account for this, the heat loss of pipes carrying liquid (water for fire extinguishing and hydraulic fluid amongst others) needs to be estimated and mitigating measures must be taken.
In this study, methodology from the refrigeration industry is applied to calculate the estimated time to freeze for liquids in pipes. The methodology is adapted for use in the maritime industry, and results are presented in this study. The methodology used was found to be quite flexible, allowing for the calculation of complex scenarios and shapes, including the effect of varying degrees of insulation on pipes, and can easily be applied for approximating the best suitable method of insulating pipes to ensure flow assurance and maintain fluid properties at desired levels. Tables estimating the time-to-freeze for insulated pipes of different diameters and insulation thicknesses exposed to cross-winds of varying speeds are provided. The methodology is found to have great potential, and should be investigated further with experiments. The objective of the paper is thus to introduce the methodology for cold-climate engineering and use it for practical analysis of realistic estimates of insulated and non-insulated piping.
