Underwater umbilical cables integrate multiple functions such as optical fiber communication, remote control command transmission, video image transmission, remote power supply, and the conveyance of working liquids and gases, serving as the optoelectronic transmission link between underwater equipment. They are not only capable of transmitting loads, energy, information, and substances to underwater equipment, but also able to withstand extreme conditions such as high pressure, high salinity, and low temperature in deep-sea environments, exhibiting resistance to seawater corrosion and wear. The use length of a single umbilical cable typically ranges from several hundred meters to several kilometers, and different models of underwater equipment operating at different depths have varying technical requirements for umbilical cables. Therefore, umbilical cable technology is complex and the manufacturing process is challenging.
The main functions of the umbilical cable used in subsea production systems include: ① providing a hydraulic power channel for subsea valve actuators; ② supplying electrical energy to control boxes, electric pumps, etc.; ③ offering a remote control and monitoring data transmission channel for subsea facilities and oil wells; ④ delivering necessary fluids (such as methanol and corrosion inhibitors) to oil wells; ⑤ transporting crude oil and natural gas from the well to the platform or onshore.
According to usage requirements, umbilical cables for subsea production systems are generally classified into dynamic cables and static cables. In the same project, the core structure of dynamic cables and static cables is the same. Dynamic cables need to withstand larger and more complex mechanical forces, and their armor design requirements are higher than those of static cables. The laying length of static cables can reach several kilometers, so it is necessary to reduce their mass and volume to meet production, transportation, construction, and cost requirements. Dynamic cables are susceptible to the influence of wind, waves, currents, and floating body movements during installation and operation, requiring local and overall mechanical analysis to ensure safe operation throughout their lifespan. In contrast, static cables usually only need to consider issues such as seabed stability.
Based on their structures, umbilical cables used in subsea production systems can be categorized into steel pipe umbilical cables, thermoplastic hose umbilical cables, electrical umbilical cables, and multifunctional umbilical cables. Steel pipe umbilical cables excel in terms of crush resistance, strength, and chemical resistance, with no liquid leakage. However, they are limited by factors such as a large bending radius, susceptibility to fatigue damage, high cost, operational difficulties, and long delivery times. In contrast, thermoplastic hose umbilical cables offer advantages such as low cost, ease of operation, and a small bending radius. However, they have lower crush resistance and poorer chemical resistance, and are prone to liquid leakage and expansion under internal pressure. Among these, super duplex stainless steel pipes exhibit low response latency and impermeability to the transmission medium, making them the preferred choice for long-length umbilical cable designs. In dynamic use environments in shallow waters or where equipment needs to be repeatedly reeled and released, thermoplastic hoses with good flexibility and a smaller bending radius are the best choice. Both types of cables have their advantages, and they are often used in combination in practical applications.