Thixotropic deepwater insulation

Balmoral Flowtherm™

Balmoral Flowtherm system is one of a range of materials which have been designed specifically to meet both the buoyancy and insulation requirements of deepwater pipeline systems.


Balmoral Flowtherm is a unique thixotropic syntactic insulation product designed for installations and applications where an adaptable solution providing stable, long term, maintenance-free insulation and/or buoyancy is required.

Designed to be rheologically-stable to operating temperatures in excess of 100°C and to pressures up to 300bar, Balmoral Flowtherm is suitable for a number of applications such as providing additional buoyancy and/or thermal insulation within compartmentalised structures in riser towers, pipe-in-pipe assemblies and dog houses. It may also be used to provide fully-recoverable temporary buoyancy during bundle or tower tow-out and installation, and may be used as a high performance insulating filler in subsea thermal blankets for retrofit insulation of seabed pipework.

Because Balmoral Flowtherm demonstrates a high Critical Yield Stress, it neither pours nor flows under its own weight or buoyancy. No material loss will occur in the event of significant rupture of the containing structure. Convection currents cannot arise within the material, allowing it to remain an outstanding thermal insulator, despite being handled as a liquid.

A selection of the measured properties of Balmoral Flowtherm is shown in the table opposite.

In addition to short-term laboratory testing, longer term testing has undertaken to determine the resistance of Balmoral Flowtherm to immersion in water at elevated temperature. Initial test data was used to provide an extrapolation of the viscosity of the base thixotropic oil over a typical service duration by means of linear regression analysis. The graph below shows that there is a minor effect on viscosity at 50°C and a minimal effect at 90°C, with in both cases an initial increase in viscosity followed by a very slow thickening over the rest of the extrapolated period. This can be taken as representative of the effect on other material properties over the analysis period.

The second graph shows a similar extrapolation, on this occasion predicting the loss of buoyancy of 1500msw-rated Balmoral Flowtherm over a 20 year period at the rated service depth. The final figure of approx. 1.95% buoyancy loss after 20 years immersion at 55°C compares very favourably with all other high temperature buoyancy systems.



Balmoral Flowtherm thixotropic deepwater insulation


Balmoral Flowtherm 3000
Parameter Value
Depth Capability msw 3000
Density kg/m³ 616
Viscosity @ 25°C @ 200 s-1 (Pa.s) 20
Thermal Conductivity @ 20°C (Wm-1K-1) 0.1203
Thermal Conductivity @ 40°C (Wm-1K-1) 0.1231
Thermal Conductivity @ 70°C (Wm-1K-1) 0.1268
Thermal Conductivity @ 90°C (Wm-1K-1) 0.1294
Thermal Stability °C 90
Bulk Modulus MPa 1940