US Patent 7123826 - Temperature Controlled Pipe Using Nanotubes

http://www.freepatentsonline.com/7123826.pdf

For pipes used to transport oil or gas undersea the ambient environment can become problematic. The low temperatures can lead to freezing of the material to be transported while the high pressures can lead to compression of the tube if the tube is not sufficiently durable. This patent teaches employing nanotube material to form a conductive layer of the tubing to heat such a tube and reduce the problem of freezing.

Claim 1 reads:

1. A flexible pipe configured to convey hydrocarbon fluids in subsea environments, the pipe comprising a tubular member formed of a plastic material, and a plurality of electrical current conductive materials dispersed in the plastic material for increasing the electrical conductivity of the tubular layer, wherein the electrical current conductive materials are carbon nanotubes.