Low-permeability hollow spheres and pipe filled with the spheres for temporary weight reduction

摘要

Pipe adapted to be installed underwater at increased ocean depths by practical pipe-laying procedures comprises a porous cement shell filled with hollow spheres that are slowly permeable to water under pressure. The cement shell is filled with a sufficient volume of the hollow spheres to make the pipe only slightly heavier than sea water, providing a reduced weight that overcomes previous difficulties in laying pipe at great depths. Over a period of time after the pipe has been installed underwater, the hollow spheres gradually fill with water and make the pipe rest stably on the ocean bottom. The preferred spheres comprise porous core spheres coated with thin coatings that partially seal the spheres to the needed degree of permeability.