New Technology to Mitigate Corrosion of Offshore Mooring Systems

The new Pacu cathodic protection system is aimed at solving challenges related to the corrosion of mooring systems for permanently moored offshore structures. Image courtesy of ICT.

Imenco Corrosion Technology (ICT) (Stavanger, Norway), a division of Imenco’s international group of companies, recently introduced its Pacu cathodic protection (CP) technology to the global market. The system is aimed at solving challenges related to the corrosion of mooring systems for permanently moored offshore structures.

Initially intended for use in the mooring chains of floating production, storage, and offloading units (FPSOs), the system is equally applicable to any mooring system, such as those on floating wind platforms or offshore aquaculture installations.

“Cathodic protection has long been an integral part of the corrosion prevention strategies for offshore steel structures, but until now, this has not been successfully extended to protect the mooring lines themselves,” says Nils Olav Digre, vice president of renewable energy.

In the past, the only solution to prolong the lifespan of these mooring chains has been to accept the corrosion with an “allowance,” and by using more steel and thicker chains. However, the rates of corrosion can be unpredictable, varying hugely across the globe thanks to differing marine environments. While costly and time-consuming replacements are options, these do not solve the underlying problem of having high turnover in the lifespan of chain and corrosion-related failure rates.

“At best, this results in significantly shorter than expected lifespans for the chains and at worst, increased failure rates and integrity issues in the mooring systems with costly, unplanned interventions to replace them,” Olav Digre says. “As floating offshore installations increase in number across other industries, this issue will present itself across the board, impacting the integrity of all systems.”

According to the company, these problems are especially prevalent in the oil and gas industry, where corrosion of the chain is a leading cause of mooring failures. In turn, this often leads to a pre-emptive replacement of these systems in FPSO units.

In response to this issue, the company says its technology has undergone significant internal and external testing. With a move from qualification to commercialization, operators can now take advantage of the full package, including computer modeling, testing, installation, and verification of protection.

Comprised of ICT’s well-known Piranha clamp and an integrated, bracket-mounted sacrificial anode, the solution aims to dramatically extend the lifespan of these chains. Applicable to any permanently moored structure, the size, shape, and spacing of the anodes—installed along the length of each chain—are engineered to mesh with the requirements of a given system.

Prior to its launch, ICT worked with a major international operator to complete a technology qualification project. The project’s objective was to de-risk an anode retrofit solution for mooring chains. According to the company, the project demonstrated that the Pacu CP system was viable. Testing documentation from the project showed a sufficiently low resistance between chain elements.

Installed safely and efficiently using remotely operated vehicles (ROVs) with a custom-built tool deployment unit (TDU), the corrosion was slowed dramatically. The effectiveness was validated through a technology qualification program with the operator, and the solution is in accordance with existing industry CP standards, according to the company.

By avoiding the need for costly workovers and ultimately enabling companies to use thinner, lighter chains, Pacu allows operators to reduce the carbon footprint of chain management and supports the industry’s drive for greener, more sustainable operations. While the system is applicable to all geographical regions, it is especially well suited to locations where problems with rapid corrosion are identified as common.

Source: Imenco,