At the low temperatures and high pressures encountered in deepwater environments, hydrates and asphaltenes can quickly form deposits that clog flowlines. Syntactic foam insulation made with 3M™ Glass Bubbles is a proven, cost-effective solution for maintaining temperature in subsea pipelines and risers, to help prevent deposition and scaling.
3M glass bubbles are inert, hollow glass spheres that are compatible with commonly-used components of subsea insulation and buoyancy systems. They are virtually insoluble in water – providing excellent utility in offshore applications. Any 3M glass bubble can be surface-treated with silane glass treatments to enhance bonding with the resin and to minimize a foam’s water pickup at high pressures. Glass bubbles are far more resistant to damage from elevated temperature, pressure and chemicals than alternative syntactic bead materials. Their low surface area per volume ratio makes high syntactic foam load levels possible.
Conventional flowline constructions, such as "pipe-in-pipe," are proving to be impractical and too costly for use at today's greater depths of 10,000 ft (3,000 m) and more. Although pipe-in-pipe offers the best U-value (insulating value) and longest cool-down times, the added weight and bulk of its construction can make it more difficult and costly to lay, and too heavy to support in deeper waters, of particular concern for risers.
As an alternative, flexible flowlines -- consisting of a single pipe coated with 3M glass bubble-filled syntactic foam insulation -- is less than half the weight of pipe-in-pipe, making it more practical for use at greater depths and in longer runs. Because this construction reduces overall pipeline subsea diameter, more pipe can be wound per spool, requiring fewer and smaller ships -- making installation faster, easier and more economical. Because of these and many other factors, wet pipe insulation now accounts for the majority of all new deep water subsea flowlines. Compared with the standard 3M glass bubble range of products, the XLD range of 3M glass bubbles allows thinner insulation on flexible subsea flowlines with the same insulation performance which enables even more pipe on a reel.
View Reprint of Offshore article “Wet insulation evolves to meet subsea flowline performance demands.” (PDF, 212 KB) Rob Hunter, 3M Oil & Gas Business. 2008.
The industry trend for deeper offshore oil production platforms has driven increasing use of wet insulation syntactic foam coatings made with 3M glass bubbles on Steel Caternary Risers (SCRs), Top-Tensioned Risers (TTRs) and riser towers, to achieve OHTC (U values) of 2 W/m^2 K and below.
At today’s greater depths, flexible flowlines made with 3M glass bubble-filled syntactic foam insulation offer a more practical, light weight alternative to conventional pipe-in-pipe constructions.
Wet Pipe Insulation
This table represents a sampling of the 3M glass bubbles portfolio of products suitable for syntactic foam insulation.
This graphic is intended to provide a rough visual guide to the conditions where they may provide the optimal balance of performance and cost.
For example, the U-values of syntactic foams formulated with 3M glass bubbles generally range from 2-12. While PiP can get down to 0.5 U-value, it comes at a much higher cost of material and installation -- so if higher U-values can be accommodated, wet pipe insulation can provide a lower cost alternative.