Page 23: of Marine Technology Magazine (April 2015)

can be vacated of air ? lled with ? uid and connected to the reservoir to maintain the pressure balance.

Corrosion Protection and Sealing

On offshore machines, it is common to have a seal, seal- ing surface, seawater, and some other medium in contact and interacting with each other. On large hydraulic cylinders, for example, maintaining the integrity of the cylinder rod, which is routinely exposed to environmental conditions in opera- tion, is essential for maintaining the long-term operating life of the system.

The rod surface needs an appropriate coating to provide a good and durable base for the cylinder’s tribological system between the cylinder head and the piston rod. There have been major advances in cylinder coating technologies, including metallic/metal mix systems applied with high velocity oxygen ? ame (HVOF) or cobalt alloy coatings applied via plasma arc welding.

In hydraulic actuator design there is always an interaction between seals, ? uid, and material surface. The study of these three items is known as tribology. Knowledge of this is criti- cal for system designers, to both keep seawater out of a sys- tem and keep the hydraulic ? uid in.

Human Safety and Environmental Protection

Equipment engineered for subsea applications must protect both people and the ocean environment from any damage.

For deep water and ultra-deep water operations, surface op- erators need protection from equipment failures during the whole life cycle of the subsea system.

Subsea operations are carried out in environmentally sensi- tive areas. Hydraulic systems that follow safety principles, such as fail-safe systems that use a de-energization principle, www.marinetechnologynews.com

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