Dredging: Excavation activity/operation carried out at least partly underwater in shallow seas or fresh water to gather up bottom sediments and disposing of them at a different location.
A dredger is a ship equipped with a dredge, a device used for removing material (scraping, sucking, lifting, etc.) of material from under water.
Why Composite for Dredgers?
Ladder and cutterhead bearings operate in a very harsh environment. Bearings must maintain a maximum in-life service time for the dredger while enduring the high abrasive content in the water and the high shock loading associated with the dredging of bedrock.
Excellent references including world’s largest dredge builder (IHC)
- Archirodon Construction (Overseas) Co.
- HUTA Marine Works Ltd.
- Jan De Nul N.V.
- Weeks Marine
- Great Lakes Dredge
- Norfolk Dredge
Composite has been used since early 1970’s
Outperform rubber by at least 2:1
Thordon ladder (cutterhead intermediate line shaft) bearings, usually Composite, offer the following benefits to the owner:
- Uses seawater for lubrication
- Eliminates grease and greasing system
- No pollution
- No clean-up after dredging
- Improved safety for crew (no slippery ladder from grease contamination)
- Lower maintenance costs
- Able to change bearing with shaft in place
- Ship's crew can change bearing
- No grease purchases
- High abrasion resistance
- Less friction; no noise or vibration
- Accommodates edge loading caused by shaft misalignment
- Greater impact resistance/resilience
Thordon Composite bearings are specially formulated to provide longer wear life in highly abrasive and dirty water conditions, such as river boat propeller shafts and suction cutter head bearings on dredges. Composite has proven to last at least twice as long as rubber bearings in extreme environments.
Ensuring reliable operation of all equipment installed above the waterline is a tough issue for any ship’s crew. Deck machinery and steering gear bearings require frequent maintenance and grease lubrication. If routine maintenance is delayed or greasing is overlooked, it has a high cost consequence for the ship owner—seized bearings can cause expensive rope replacement, safety issues as a result of manual greasing, and vibration causing damage to the piston and cylinders.
ThorPlas-Blue is a maintenance-free solution, eliminating a source of pollution. The proprietary engineered thermoplastic bearing is capable of pressures up to 45MPa (6,527 psi); higher pressures may be possible with Thordon Engineering review. ThorPlas-Blue can easily be back fit into virtually all applications where greased bronze is currently installed. A stainless steel or non-corrosive mating surface should be used.
Working body grapple with mounted ThorPlas-Blue bearings
Intermediate Lineshaft Cutterhead Bearings
Installed in November, 2011 on CSD Athena owned by Van Oord, NL
Another set installed on CSD Artemis, April 1, 2013