A constant quantity of air is supplied from the air source. It passes through #2/3 chamber and is spouted into sea by lifting #1 and #2 rings. The air pressure in #2/3 chamber is always maintained about 0.1 bar greater than the sea water pressure so to slightly exceed the tightening force of #1 and #2 rings.
The air pressure is added to stern tube oil tank. The oil tank is installed at 3 meter above a shaft center. The stern tube oil pressure becomes “air pressure in #2/3 chamber + 0.3 bar” and it also follows the draft change. Any draft change can be automatically detected and the air pressure in #2/3 chamber and stern tube oil pressure follow the draft change instantly.

• ABS,LRS,DNV(etc.) Pollution free class
• Longer seal ring life due to pressure balance

Advanced Technology of Propeller Shaft Stern Tube Seal Presented at the Propellers/Shafting 2003 Symposium of the Society of Naval Architects and Marine Engineers (SNAME) in Virginia Beach, VA on September 17-18,2003.