Case Study
Building Seaworthy Hydraulic Cylinders By Peter Claessens, Customer Support & Supply Chain Manager, Danfoss Power Solutions
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loating liquefied natural gas vessels are used in offshore operations to produce and store liquefied natural gas before it’s transferred to tankers for transport to the mainland. To ensure the stability of these vessels, large hydraulic cylinders are often deployed in mooring tensioner systems. A floating liquefied natural gas (FLNG) compression and storage vessel for a high-profile offshore venture in West Africa needed 12 custom cylinders for its mooring tensioners. There were a number of requirements for the project: the cylinder supplier had to be capable of and highly experienced in producing extra-large custom hydraulic cylinders; it needed to have technically advanced, reliable solutions that would withstand the corrosive saltwater environment for decades of anticipated use; and it needed to be a collaborative partner to ensure project success. The company found its solution with long-time cylinder manufacturer Eaton Hydraulics, now part of Danfoss Power Solutions. At work in some of the world’s toughest applications across demanding sectors like oil and gas, civil engineering, and discrete manufacturing, Danfoss’ extra-large hydraulic cylinders are known for their quality, reliability, and advanced technology.
Project challenges Off the coast of West Africa, the FLNG vessel played a crucial role in a venture the company was supporting. Any issue with the ship’s stability could disrupt the entire project, creating not only safety concerns but also a considerable loss of time and money for all the stakeholders involved. With the stakes already high, the company’s requirements created some unique technical challenges. The mooring system, which compensates for the motion of the waves, called for extra-large cylinders in an atypical horizontal orientation, requiring a custom solution. Brutal offshore conditions complicated matters. Not only did the cylinders have to withstand continuous exposure to saltwater and sea spray, they also had to endure blowing sand from the Sahara desert in high wind conditions. With project operations expected to run for up to three decades, the solution had to perform well and be incredibly resilient. 8
MAY 2022
Mooring tensioners provide stability in brutal sea conditions.
Engineers from Danfoss collaborated closely with the company for several weeks to develop a custom system. This close working relationship enabled Danfoss engineers to gain a thorough understanding of the company’s requirements and design the best solution. Starting with the basics, 12 carbon steel hydraulic cylinders with built-in accumulators were specified for the FLNG vessel mooring system. Featuring a 600-millimeter diameter and 4,500-millimeter stroke length, the sizable cylinders have a design pressure of 230 bar (3,335 psi). Each is equipped with high-grade stainless steel piping and manifold blocks. The team next turned to solutions for corrosion protection, a critical consideration for cylinders used in offshore environments. Corrosion can impair cylinder performance and even lead to failure, resulting in unwanted downtime while raising safety and environmental concerns. Costs can skyrocket with even one day of downtime in offshore installations, emphasizing the importance of equipment reliability and ease of maintenance.
Corrosion protection Danfoss’ Eatonite anticorrosion laser cladding was specified as the cylinder rod coating. This proprietary, high-performance coating offers superior corrosion resistance in saltwater operations as well as optimized wear, scratch, and impact resistance. The material is very dense and allows no access to the base piston rod material, which is the usual cause of corrosion and coating failures. Originally developed for hydraulic riser tensioning systems on offshore platforms, Eatonite laser cladding was the first anticorrosion coating technology to earn DNV certification. The technology has been proven through more than 10 years of use in the field with no failures. WWW.FLUIDPOWERJOURNAL.COM • WWW.IFPS.ORG
