Large amounts of time, effort and money have been spent investigating the practical feasibility of using carbon steels as materials of construction for long-distance pipeline transmission and distribution of high-pressure (500-3000 psi) hydrogen. Most of the hydrogen produced today is transported short distances through relatively small-diameter pipes at pressures of just a few hundred psi. For this purpose, pipes made of carbon steel are perfectly adequate. However, at internal gas pressures above ~500 psi, carbon-steel pipes are susceptible to hydrogen embrittlement, which is typically manifested by surface cracking, crack propagation, decreases in tensile strength, loss of pipeline ductility, and reduced burst-pressure rating. This degradation can lead to premature failure of one or more segments of a pipeline, resulting in leakage of gas—or in extreme circumstances, bursting of a pipe.

It has been suggested recently that many of the cost, weight, welding and joining, repair, and safety issues associated with hydrogen transport through carbon-steel pipes can be resolved by switching to fiber-reinforced polymer (FRP) materials. To have sufficient mechanical strength and hydrogen-containment capability, a FRP pipeline segment would probably consist of an inner, low-permeability barrier tube that transmits the high-pressure hydrogen gas, a protective layer placed over the barrier tube, an interface layer placed over the protective layer, multiple glass- and/or carbon-fiber composite layers, an outer barrier layer, and an outer protective layer. The issues and challenges for adapting existing FRP pipeline technology to hydrogen service at pressures above ~500 psi are: evaluating polymeric materials for hydrogen containment and compatibility; identifying methods for profitable manufacture of pipes with inside diameters >4 inches; weighing the options for on-site pipeline joining and repair; determining the availability of sensor technologies for measuring gas temperature, pressure and flow rate in real time; and writing the necessary codes and standards to meet the requirements of local, state, and federal regulatory agencies.

Thus, it is significant that scientists at Hydrogen Discoveries, Inc. have invented new methods of materials fabrication, structural design, and component/facility construction that greatly reduce the diffusive flux of hydrogen gas through the walls of hollow cylinders. The techniques involve: (1) use of one or more layers of homogeneous or laminated polymeric material, solid metal(s) and/or liquid(s), to create multiple equilibrium and kinetic barriers to hydrogen diffusion; and (2) in special circumstances, physical separation of gaseous hydrogen from one or more static or flowing liquid interlayers. The various embodiments of the invention have numerous practical applications in transmitting and distributing pressurized hydrogen gas through pipes, pipelines, tubes and hoses of various lengths, internal diameters, and wall thicknesses.

Rigorous theoretical modeling of hydrogen flux through multi-layered polymer/metal pipes indicates that thin layers of copper will be particularly effective in decreasing overall gas permeability. Therefore, three- and five-layer polymer/copper/polymer structures, with inner and outer layers of polymer protecting the thin copper layer(s) from chemical attack and mechanical abrasion, are of particular interest in designing FRP pipes, tubes and hoses for hydrogen service.