Lessons From Under the Sea Water Lubricated, Seal Free Bearings for Wave & Tidal Energy
Representing Thordon Bearings Inc. 30+ years experience designing and manufacturing pollution-free bearing systems for: Marine Market Offshore Market Pump Market Industrial Market Hydro-turbine Market Wave & Tidal Energy Market
History Water lubricated bearings date back to earliest days of shaft driven propellers and hydroelectric turbines in mid- 1800 s. 3
History Before the introduction of effective seals, all ships and hydro turbines were designed to operate with water lubricated shaft lines The best water lubricated bearing solution of the time was lignum vitae (a tropical hardwood) 4
History With increasing propeller driven ship construction, seal technology was advancing, and oil lubricated bearings replaced the wood. 5
History BUT, grease or oil lubricated systems are only as good as the seal that must keep the water out and the oil in to ensure the shaft keeps running! Water lubricated/self lubricated bearing technology was also advancing and for survivability Naval ships began to move back to water lubricated bearings Water lubricated bearings are now widely found in naval and commercial ship propulsion and steering systems, as well as conventional hydro turbine design. 6
Propeller Shaft Bearings Moderate load, continuous rotation, high speed Bearing pressure up to 0.5 Mpa, fully hydrodynamic water film supports the load Shaft size from Ø100 mm up to Ø1000mm Speeds from 10 rpm up to 250 rpm Water Lubricated Bearings
Propeller Shaft Bearings Water Lubricated Bearing Support Positions 8
Typical Water Lubricated Elastomer Bearing 9
Canadian Navy 12 Canadian Navy Patrol Frigates (Halifax Class) equipped with water lubricated elastomer propeller shaft bearings since 1994. 10
8 Australian Navy ANZAC Frigates equipped with Water Lubricated Elastomer Propeller Shaft Bearings since 1995 11
Rudder Bearings High load, oscillating rotation, low speed Disney Magic Bearing pressure up to 10 Mpa, sliding friction operation non-hydrodynamic Shaft size from Ø100 mm up to Ø1000mm Speeds from 0 to 3 rpm Radial bearings carry side loads, thrust or carrier bearings support hanging loads (weight of rudder) May operate wet or dry (using self-lubricating bearing material)
Rudder Bearings Typical Large Rudder Combined Thrust & Radial Rudder Bearing Assembly 13
Typical Rudder Bearing Installation
USS Nimitz equipped with self-lubricated elastomer rudder bearing since 1998. 15
A.P. Moller (Denmark)Emma Maersk equipped with Thordon SXL rudder bearing since 2006. 16
Kaplan Hydroelectric Turbine Wicket Gate Control Mechanism Water Lubricated Main Shaft Bearing
Complete Shaft Bearing Assembly Low load, continuous rotation, high speed Bearing pressure up to 0.3 Mpa, fully hydrodynamic water film supports the load Shaft size from Ø100 mm up to Ø2000mm Speeds from 10 rpm up to 400 rpm 18
Wicket Gate Control Mechanism Bearings High load, oscillating rotation, low speed Bearing pressure up to 30 Mpa, sliding friction operation non-hydrodynamic Shaft size from Ø25 mm up to Ø450mm Speeds from 0 to 3 rpm May operate wet or dry (using self-lubricating bearings)
Wave & Tidal Applications Relevant Applications in Wave & Tidal Technologies
Why is water lubrication a good fit for Marine Energy Technologies? Almost every device incorporates some rotating, pivoting, sliding, or oscillating elements Rolling element or oil filled plain bearings can be used but as with ships, they all require sealing to keep the oil in and sea water out Marketed as a source of clean energy, these devices must not pollute the rivers or oceans Simplicity & reliability is key to success all are looking for at least 5 year service intervals, and 25 year life 21
Tidal or In-Stream Hydrokinetic Blade Pitch Bearings Radial & Axial Bearings to Support Rotor 22 Images from www.aquaret.com
Tidal or In-Stream Hydrokinetic Upper & Lower Radial Bearings Low Speed Pivot Bearings 23 Images from www.aquaret.com
Wave Energy Devices Sliding Bearing, Pads or Cylindrical Form Pivot/Hinge Bearings 24 Images from www.aquaret.com
Wave Energy Devices Water lubricated main bearing for Kaplan type turbine Water lubricated bearing for air turbine in OWC device 25 Images from www.aquaret.com
Mooring Connections Low Speed Yaw/Swivel Connection Bearing to React Radial & Thrust Mooring Loads 26 Images from www.aquaret.com
Conclusion Water lubricated bearings are a proven alternative to oil and grease lubricated bearings, with a long history of success in underwater machinery Bearing design must be approached differently than if using rolling element bearings, so need to consider early in the design process Plain bearings can offer reliability, simplicity, and cost advantages Using water lubrication eliminates the risk of sudden bearing seizure or pollution as a result of seal damage or failure 39