The objective of this continued research is to further validate that an IICP insulation system incorporating a low thermal conductivity, high strength wire screen mesh between a pipe and an interior liner can be an effective passive thermal insulation solution for deepwater flow lines and risers. Phase II will confirm the low thermal conductance values measured with coupons in Phase I are also attainable for pipes and demonstrate IICP performance under steady and transient flow conditions. Results will be used to interest industry and contractors in this technology.
Phase I, completed in June 2005, demonstrated that a thermal resistance is created at the interface between two materials, in this case a pipe and a liner, due to the surface metrology (roughness) of the contacting surfaces. If the two contacting surfaces are separated by a screen wire or mesh at the pipe and liner interface, the resistance to thermal transport is increased significantly. The screen wire reduces heat transfer by restricting the path available for conduction and forms a stagnant air gap to minimize radiation and convective heat transfer. Heat transfer was further reduced by adding a Mylar film to the exterior of the liner and the interior of the pipe wall. This further reduces the surface contact area between the wire screen mesh and pipe wall, and similarly, reduces the surface contact area between the mesh and liner wall; therefore, increasing the restrictive path for conduction. Moreover, the low thermal conductivity Mylar film adds additional layer of resistance. Experiments with coupons of pipe/mesh/liner materials showed that the thermal conductivity can be reduced up to 50 times lower than the pipe material. Preliminary experimental data showed further enhancement in thermal resistance of appropriately 20% with the Mylar film present. A comparison of the overall thermal conductance has been modeled for a design which incorporates the interstitial wire-screen with and without existing insulation material (e.g., polyolefin foam). The calculated effective thermal conductivities from experimental conductance data compare favorably with insulation technologies presently used for subsea applications. The Phase I final report was provided to MMS on February 24, 2006 and is available for public view and download from our REPORTS section below.
Under Phase 2, laboratory experiments on a small scale prototype IICP have been conducted to validate the IICP concept in the prototype geometry (i.e. pipe versus coupon), and demonstrate its effectiveness as a means to insulate deepwater pipelines, flow lines, and risers. The IICP design parameters (wire screen diameter size, mesh number and Mylar film thickness, joint interface pressure) were based on information learned from the Phase I experiments. During Phase II, a model to estimate the thermal performance of the IICP system for pipeline, flow line, and riser examples under realistic conditions was developed and calibrated with experimental data and used to assess the performance of the IICP system in a variety of steady flow and transient shut-down scenarios. Analytical studies using these results was shared at the 2006 Offshore Technology Conference in Houston, TX; winning favorable interest from many pipeline operators and owners and is expected to gain industry support for continued development . The IICP insulation system is comparable with other insulation systems presently used for subsea pipeline, flow line, and riser applications, and subject to further development may prove to be less expensive, easier to install, and more robust than present insulation technologies. The Phase II Final Report is expected soon unfortunately due to the proprietary nature of the work only a summary of the results will be posted on this website.
Phase 3 of the investigation is now underway and involves the construction, assembly, and testing of an initial prototype pipe section as an intermediate stage towards a conventional size pipe for actual applications. The prototype was constructed with cold and hot loops to simulate an actual working environment with hot water as the crude oil and a coolant as the seawater. The prototype section has a 4-inch outer diameter pipe and a 3-inch inner diameter pipe. The pipe section, which is three feet long, was manufactured by Stress Engineering, Houston, TX. The annular space has two layers of stainless steel screen wire mesh separated by a thin aluminum layer that acts as a radiation heat transfer barrier. Steady State and Transient Test runs have been conducted to investigate the performance characteristic of the insulation technology under the following conditions. Further data sets are being collected for various flow rates and boundary conditions for analysis of detail performance characteristics such as thermal conductivity, thermal diffusivity, and thermal conductance for the various combinations tested.