Subsea risers work similarly to pipelines, but transfer material vertically. On offshore platforms, a riser runs from the seafloor to the deck platform. Like the pipelines, they have to be able to sway within the current. Critical sections of the risers feature tapered stress joints to spread heavy loads.
Automated Dynamics, part of Trelleborg Group, provides many structures for this market, including structural insulators for the stress joints made from continuous S-2 fiberglass-reinforced polyetheretherketone (PEEK) impregnated tape. “These structural insulators transfer load while protecting against galvanic corrosion between dissimilar metals in the presence of seawater,” explains Brett Kimball, program manager for Automated Dynamics.
Corrosion Resistance from the Inside Out
The impact of environmental conditions on structural integrity is usually at the forefront of discussions between composites fabricators and end users. “Often the issues our products face are from severe environments, whether that’s a land-based well or an oil rig that is dusty and dirty and gets a lot of contaminants … or a marine environment that means exposure to sea water, barnacle growth and things like that,” Jacoby says.
Yet one of the most demanding challenges placed upon materials in oil and gas applications doesn’t come from the outside environment. In many cases, it’s the caustic material being transported within pipes or held in tanks that does the greatest damage.
Netherlands-based TenCate Advanced Composites’ products are commonly used in high-energy oil extraction alternatives to hydraulic fracturing, explains Steve Johnson, the company’s thermoset product manager. “Primarily, we’re focusing on transmissive applications, where you want low dielectric materials that you’re going to be putting energy through,” he says. For example, the company provides glass and high-density polyethylene (HDPE) thermoplastic unidirectional tapes that reinforce oil and gas pipes. The composite materials help the piping systems resist corrosion at a much lighter weight compared to metal piping.
“The environments where you have severe hot-wet with chemicals, acid and alkali are definitely a challenge. But the truth is the types of systems from which you can get the high transmissivity – and low dielectric loss – are attacked very strongly by those types of conditions,” says Steve Johnson. “So you have to have either a material that’s going to have a short lifetime or those materials are coated with something impervious, like something akin to Teflon™.”
This is the niche that TenCate works to serve, but Steve Johnson points out that the rapid breakdown typical composite solutions face in these intense environments may challenge broader use of these materials.