Seals for a New Era of Submarines
Whenever a revolutionary technology is introduced, there follows a wave of activity in adjacent fields as supportive technologies are updated to meet the demands of the new cutting edge. When it was discovered that nuclear energy was a viable option for powering submarines, there were many other aspects of conventional submarine design that had to change. Among the most critical areas of focus were the many sealing mechanisms essential to submarine design.
With the first nuclear-powered submarines, 1955’s Nautilus Class, specific seal technologies were required for high-pressure containment, shaft sealing, and general leak prevention. These included flexible graphite seals for durability and performance, O-ring and bulkhead seals for watertight barriers, and specialized spring-energized metal seals for critical components like the reactor pressure vessel and valves. Other essential seals include those for hydraulic systems and the propulsion shaft, which must prevent seawater intrusion.
Now, a new class of nuclear submarine has emerged, and along with it, newly developed innovations in mechanical seal technology.
Depth, Duration, Dependability: Putting the Pressure on Seal Tech
With the new Virginia-class of nuclear-powered submarines, the US Navy needed a new generation of mechanical seals to support these ships through more demanding undersea missions. Here are the key innovations developed to help the Virginia Class Submarines go faster, deeper, and farther, with less maintenance and greater stealth than ever before:
Primary Sealing System–Mechanical Face Seals
Modern face seals perform at a higher level due to materials such as: carbon-graphite, silicon carbide, advanced polymers, titanium, Inconel, Silicon Carbide (SiC), Tungsten Carbide (WC), and Diamond-Like Carbon (DLC) Coatings
Hybrid Systems
Combining different materials and sealing mechanisms creates robust hybrid systems that can leverage the strengths of metal alloys and advanced polymers in different parts of the seal assembly.
Integrated Monitoring Systems
Modern seals can integrate intelligent monitoring systems with sensors that track temperature, pressure, vibration, and leakage in real-time. This allows for predictive maintenance, preventing catastrophic failures and optimizing operational efficiency.
Optimized Flushing and Cooling
Seal designs now feature improved internal pathways for flushing and cooling fluids. Direct flushing to the seal faces prevents the accumulation of abrasive particles, which increases seal longevity and minimizes leakage.
Fully Split Cartridge Designs:
A major operational advancement is the adoption of fully split mechanical seals. This design allows for easier installation, repair, and replacement without the need to dismantle large pieces of equipment (such as the propeller shaft), dramatically reducing maintenance time and costs.
Re-Thinking of Everything
Cartridge Construction
Integrated cartridge design simplifies installation, lowers the maintenance burden, and reduces downtime while ensuring an accurate seal setting.
Hydraulically Balanced Designs
Hydraulic balancing permits non-contacting faces, which dramatically improve reliability by limiting wear and reducing required maintenance.
Triple Redundancy
Three seals are arranged in a series, with each being capable of handling 100% of the system pressure on its own, should the two others fail.
Protection from Electrical Issues
Shaft grounding rings can be installed to mitigate damage caused by stray electrical currents generated by friction between the two faces of the primary seal.
