Stern Tube Bearing
critical
IMO Required
33 models total
The stern tube bearing supports the propeller shaft where it passes through the hull, in the one place on the shaft line hardest to inspect without dry-docking, and its condition decides how long the shaft line runs without unplanned downtime.
Read more — Stern Tube Bearing explained ▾
What a stern tube bearing does
The stern tube bearing supports the propeller shaft where it passes through the hull, taking the propeller's weight and the radial loads from propeller thrust and shaft misalignment, in the one place on the shaft line that is hardest to inspect or repair without dry-docking. Its condition, more than almost any other single component, decides how long the shaft line runs without unplanned downtime.
Main components
Bearing bush
A cylindrical bearing shell, traditionally lined with white metal for oil-lubricated systems or with a synthetic rubber or resin-based compound for water-lubricated systems, fitted inside the stern tube to carry the shaft.
Lubrication system
Oil-lubricated stern tubes run a sealed oil system with a header tank providing a static head above sea pressure, oil coolers, and filtration; water-lubricated systems rely on the surrounding sea water itself, fed through grooves in the bearing liner, and depend on the shaft turning to maintain a film rather than on a separate oil circuit.
Shaft seals
Aft seal keeps sea water out of an oil-lubricated stern tube, or, on water-lubricated systems, is arranged differently since water ingress into the bearing is expected; forward seal keeps stern tube oil out of the engine room bilge. Seal design ranges from lip seals to face-type mechanical seals on newer installations.
Wear-down monitoring
Most vessels carry a wear-down measurement point, a mechanical gauge or increasingly a permanently fitted sensor, to track bearing clearance increase over time without opening the stern tube, since clearance growth is the main indicator of remaining bearing life.
Selection and sizing
Bearing material and lubrication type follow from the shaft diameter, propeller-induced loading, and environmental rules the vessel trades under: white-metal oil-lubricated bearings remain common on larger, higher-powered vessels; synthetic water-lubricated bearings have grown in use, partly driven by regulation restricting oil discharge risk from stern tubes. Bearing length-to-diameter ratio, clearance tolerance, and permissible wear-down before renewal are all set against the shaft manufacturer's and class society's design values.
Regulations and class
MARPOL Annex I and the broader push to reduce oil pollution risk have driven a shift away from oil-lubricated stern tubes with a direct discharge risk toward water-lubricated or environmentally acceptable lubricant systems on newer builds, and several class societies and flag states set stricter monitoring requirements for oil-lubricated systems as a result. Class rules require periodic survey of the stern tube bearing, including wear-down measurement, at intervals tied to the vessel's survey cycle, with shaft withdrawal or in-situ inspection depending on class notation and monitoring system fitted; continuous survey notations can extend the interval between withdrawals where approved condition monitoring is in place.
Typical faults
- Excessive wear-down beyond class limits: found at routine measurement, requires bearing renewal, often meaning shaft withdrawal and dry-docking.
- Aft seal failure on oil-lubricated systems: sea water ingress into stern tube oil, or oil leakage into the sea, both reportable and both accelerating bearing wear.
- Overheating from inadequate lubrication or misalignment: babbitt bearing wiping damage that shows up as a sudden clearance jump rather than gradual wear.
- Vibration from shaft misalignment transmitted into the bearing: accelerated, uneven wear pattern rather than the expected uniform wear-down.
- Water-lubricated bearing dry-running at very low shaft speed or during prolonged stops: accelerated wear of the liner surface.
What to look for in a supplier
- Bearing material and clearance specification traceable to the shaft manufacturer's design and the vessel's class notation.
- Wear-down monitoring system compatible with the vessel's survey regime, particularly if aiming for a continuous survey notation to extend withdrawal intervals.
- Documented compliance route for oil-lubricated systems under current MARPOL Annex I discharge provisions, or a water-lubricated or EAL alternative if the trade requires it.
- Seal system proven for the vessel's shaft speed and draft range, since seal failure is the most common route to bearing damage.
Trend the wear-down readings over successive surveys rather than judging each one in isolation: a bearing that is within limits but accelerating toward them tells the real story before it becomes an unplanned dry-docking.
5 yr
Class Survey
15 yr
Typical Lifetime
Typical Manufacturers
Thordon
Duramax
Wartsila
14 manufacturers · 33 models
SKF Marine
11
Bulkhead seals, split and not split version and its design
Per propulsion shaft design
· Propulsion Shaft Line
· Split bulkhead seal
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Modular split design enables installation or replacement without dismantling the entire stern tube
- SKF’s high‑quality bearing materials give low friction and long service life under normal sea conditions
- DNV‑approved design meets recognised classification society standards
- Standardised dimensions simplify integration on new builds and retrofits
- Compatible with routine oil analysis programmes for condition monitoring
Weaknesses
- Abrasive particles in coastal or shallow water can accelerate bearing wear
- Seal leakage will cause oil loss if daily drain inspection is missed
- Precise shaft alignment is required; mis‑alignment leads to uneven wear
- Higher upfront cost compared with basic non‑SKF bulkhead seals
- Split version adds additional sealing surfaces that must be correctly torqued
Typical Vessels:
Bulk CarrierTankerContainer ShipOffshore Supply VesselRo‑Ro Ferry
Certifications:
DNV
Decision Guide: Choose if: the vessel operates primarily in open sea or deep water, you need a proven DNV‑approved seal that can be serviced without full stern tube removal, and regular maintenance (daily drain check, quarterly oil analysis) is feasible. Avoid if: the ship spends most of its time in sand‑laden shallow waters, maintenance windows are scarce, or budget constraints preclude the higher initial cost.
Use Cases: Installed on the stern tube bearing of low‑ to medium‑speed propulsion shafts to protect the bearing oil from seawater ingress and prevent oil discharge. Commonly used on new builds and retrofits where a reliable, class‑approved seal is required for cargo vessels and offshore support ships.
CENTRAX, CENTRAX-FC, CENTRAX-FG, CENTRAX-FB, Option: -A (adapter ring)
Per propulsion shaft design
· Propulsion Shaft Line
· Integrated stern‑tube bearing & seal
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Fully integrated bearing‑seal unit reduces installation time and alignment errors
- Modular adapter ring (option A) allows retrofit on existing shafts
- High load capacity suitable for medium to large propulsion systems
- DNV‑approved design provides recognized class society acceptance
- Proven track record with extensive service data from commercial fleets
Weaknesses
- Sensitive to abrasive particles; wear accelerates in sand‑laden shallow water
- Seal leakage can occur if daily drain inspection and oil analysis are neglected
- Higher upfront cost compared with separate bearing‑and‑seal solutions
- Limited to shaft sizes covered by the CENTRAX product range
- Requires specialised tooling for removal/replacement
Typical Vessels:
Bulk CarrierTankerContainer ShipOffshore Supply VesselFerry
Certifications:
DNV
Decision Guide: Choose if: you need a reliable, class‑approved stern tube bearing with integrated sealing for medium to large commercial vessels and can commit to regular oil analysis and seal inspection. Avoid if: the vessel operates primarily in sand‑rich shallow waters without adequate filtration or if budget constraints preclude the higher initial investment.
Use Cases: The CENTRAX series is commonly installed on new builds and retrofits of merchant ships where long‑duration voyages demand low maintenance and high reliability, especially in open‑sea or moderate coastal operations.
Models: Turbulo Mechanical Phase Breaker (TMPB) 0.25, 0.50, 1.0, 2.5, 5.0, 7.5, 10.0, 15 ppm Separator
Per propulsion shaft design
· Propulsion Shaft Line
· Centrifugal mechanical phase separator
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- No electrical power required – fully mechanical operation reduces failure points.
- Achieves very low water content (0.25–15 ppm) suitable for high‑sensitivity stern‑tube bearings.
- Compact, modular design allows installation in limited engine‑room spaces.
- Proven reliability on long‑haul vessels; low maintenance interval (oil analysis quarterly).
- Compatible with a wide range of fuel grades and can handle sand/sludge loads typical of coastal operations.
Weaknesses
- Higher upfront cost compared with simple coalescer filters.
- Requires periodic manual cleaning of the separator bowl to maintain efficiency.
- Performance drops if inlet flow is highly turbulent or if water content exceeds design limits.
- Installation may need minor modifications to existing fuel‑line layout.
- Mechanical wear parts (rotor bearings) require scheduled inspection and replacement.
Typical Vessels:
TankerBulk CarrierContainer ShipCruise VesselOffshore Supply Vessel
Certifications:
DNV GL Type ApprovalABS Approved Equipment
Decision Guide: Choose if: you need a proven, power‑free solution to achieve sub‑10 ppm water levels and protect stern‑tube bearings on vessels operating in coastal or offshore environments. Avoid if: space is extremely constrained, budget limits capital expenditure, or the vessel already uses an integrated electric separator that meets water‑content requirements.
Use Cases: The TMPB is typically installed upstream of the main fuel filter on large ocean‑going tankers and bulk carriers where low water content is critical for bearing life. It is also used on cruise ships and offshore supply vessels that run on heavy fuel oil with high sand or sludge content, providing a mechanical safeguard against water ingress and bearing wear.
SIMPLAN-C, SIMPLAN-C-P, SIMPLAN-SiC, SIMPLAN-SiC-P
Per propulsion shaft design
· Propulsion Shaft Line
· Stern tube bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- High wear resistance – alloy steel rollers and cages designed for sand/shale environments
- Integrated double‑seal system (SIMPLAN‑C‑P / SIMPLAN‑SiC‑P) reduces oil leakage risk
- Modular construction allows quick replacement during dry‑dock periods
- Proven DNV class approval ensures compliance with major classification societies
- Low maintenance – routine oil analysis and clearance checks suffice for most operations
Weaknesses
- Sensitive to misalignment; excessive shaft runout accelerates uneven wear
- Cavitation erosion can occur on adjacent propeller blades if seal pressure is not properly set
- Standard bearing sizes may be oversized for very small vessels, adding unnecessary weight
- Requires regular oil drain inspection to prevent environmental leakage in coastal service
Typical Vessels:
Bulk CarrierOil TankerContainer ShipGeneral Cargo VesselOffshore Supply VesselCruise Ship
Certifications:
DNV
Decision Guide: Choose if: the vessel operates in coastal or shallow‑water routes where sand and silt are common, you need a bearing with integrated sealing to minimise oil loss, and DNV class approval is required. Avoid if: the propulsion system experiences high shaft misalignment or extreme cavitation conditions that exceed the seal’s pressure capability.
Use Cases: The SIMPLAN series is typically installed in the stern tube of medium‑speed diesel‑driven ships, providing reliable journal support for shafts ranging from 300 mm to 800 mm diameter. It is favoured on vessels that dock frequently because its modular design shortens replacement time, and on ships where environmental regulations demand tight oil‑containment.
SIMPLAN-SC (combination of SIMPLAN axial and SIMPLEX radial)
Per propulsion shaft design
· Propulsion Shaft Line
· combined axial‑radial stern tube bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Integrated axial and radial load handling reduces the number of separate components on the shaft line.
- SKF’s proven bearing material and design give high load capacity and low friction, extending service intervals.
- DNV‑approved design simplifies classification approval for new builds and retrofits.
- Modular seal options allow tailored protection against oil leakage in various operating environments.
- Standardised mounting dimensions facilitate installation on a wide range of shaft sizes.
Weaknesses
- Higher initial purchase cost compared with single‑function bearing solutions.
- Sensitive to abrasive particles; sand or silt ingress can accelerate wear (known issue in coastal/shallow water).
- Installation requires precise alignment; misalignment leads to uneven wear and premature failure.
- Seal maintenance is critical – daily drain inspections are required to avoid oil loss.
- Limited to shaft diameters covered by the SIMPLAN‑SC catalogue; may not suit very large or very small shafts.
Typical Vessels:
TankerBulk CarrierContainer ShipGeneral Cargo VesselOffshore Supply Vessel
Certifications:
DNV
Decision Guide: Choose if: you need a reliable, DNV‑approved bearing that handles both axial and radial loads in one unit, operating primarily in open sea or moderate conditions, and you can commit to regular seal inspection. Avoid if: the vessel operates frequently in sand‑laden shallow waters without additional filtration, or if budget constraints prohibit the higher upfront cost.
Use Cases: The SIMPLAN‑SC is typically installed on newbuilds with medium‑speed diesel propulsion systems and on retrofits where existing stern tube bearings are being upgraded for better load distribution and seal performance. It is common in vessels that require long intervals between overhauls and where classification societies demand integrated bearing solutions.
Simplex-Compact SC3 Pod seals
Per propulsion shaft design
· Propulsion Shaft Line
· compact stern tube bearing & seal
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- High load capacity in a reduced axial length – suitable for space‑constrained pod installations
- Integrated double‑lip seal reduces external sealing components and simplifies installation
- SKF’s proprietary bearing material offers good wear resistance under moderate abrasive conditions
- Standardised mounting dimensions facilitate retrofit on existing vessels
- DNV‑approved design provides recognised classification acceptance
Weaknesses
- Sensitive to high sand or silt concentrations; abrasive particles can accelerate bearing wear in shallow‑water operations
- Seal leakage may occur if daily drain inspections are missed, leading to oil loss and environmental concerns
- Alignment tolerance is tight – misalignment of the shaft can cause uneven wear and premature failure
- Limited to low‑to‑moderate power ranges; not suitable for high‑power main‑propulsion shafts on large carriers
- Replacement requires dry‑dock or at‑sea specialized tooling, increasing maintenance downtime
Typical Vessels:
Coastal tankerFerryOffshore supply vesselPatrol boatSmall container feeder
Certifications:
DNV
Decision Guide: Choose if: the vessel uses a podded propulsion unit with limited stern‑tube space, operates mainly in open or moderate coastal waters, and requires a DNV‑approved compact bearing solution. Avoid if: the ship frequently navigates high‑silt, sand‑laden shallow waters, demands very high shaft power, or cannot guarantee daily seal drain inspections.
Use Cases: The SC3 is typically installed on podded drives of ferries, offshore support ships and coastal tankers where space savings are critical. It is favoured in fleets that already use SKF bearing monitoring systems and perform regular oil analysis and seal drainage checks during dockings.
Simplex-Compact Stern Tube Seals, Types SC2 and SC3
Per propulsion shaft design
· Propulsion Shaft Line
· Compact stern tube bearing with integrated double‑lip seal
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Very short overall length – saves space in the hull and reduces stern‑tube weight
- Integrated bearing and seal from a single supplier simplifies procurement and installation
- SKF rolling‑element technology delivers low friction losses and high reliability
- Designed for easy daily drain inspection and quarterly oil analysis, supporting condition‑based maintenance
- Suitable for low to medium power shafts (up to ~8 MW) on short‑sea and coastal vessels
Weaknesses
- Maximum load capacity lower than larger conventional stern tube bearings – not ideal for high‑power (>10 MW) propulsion systems
- Abrasive particles (sand, silt) can accelerate seal wear if filtration is inadequate
- Requires regular oil drain and analysis; maintenance effort higher than a simple plain bearing
- Retrofit may need SKF‑specific housing dimensions, limiting applicability on older ships
- Seal lip wear can lead to oil leakage if daily inspections are missed
Typical Vessels:
Bulk CarrierProduct TankerFeeder Container ShipGeneral Cargo VesselOffshore Supply VesselFerry
Certifications:
DNV
Decision Guide: Choose if: the vessel uses a low‑to‑medium power shaft (≤8 MW), space in the stern tube is at a premium, and you prefer an integrated bearing‑seal solution from a reputable supplier with proven class approval. Avoid if: the propulsion power exceeds the load rating of the SC2/SC3, the operating area has high concentrations of abrasive sediments without effective filtration, or you need a minimal‑maintenance plain bearing.
Use Cases: The Simplex‑Compact units are commonly installed on new builds and refits of short‑sea bulk carriers, product tankers, feeder container ships and offshore supply vessels where a compact stern tube arrangement is required. They are favoured in coastal and inland waterway operations where shaft length must be minimised but reliable oil‑lubricated bearing support is still essential.
Simplex Stern Tube Bushes
Per propulsion shaft design
· Propulsion Shaft Line
· simplex stern tube bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Proven SKF design with long service history in merchant vessels
- Integrated oil lubrication channel reduces friction and wear
- Standardised dimensions simplify replacement and retrofit
- SKF global after‑sales support and spare‑parts availability
Weaknesses
- Higher upfront cost compared with basic plain bushings
- Requires regular oil analysis and seal inspection to avoid leakage
- Limited to medium‑speed propulsion ranges; not optimal for high‑speed craft
- May need custom adapters for non‑standard shaft diameters
Typical Vessels:
Bulk CarrierTankerContainer ShipGeneral Cargo VesselOffshore Supply Vessel
Certifications:
DNV
Decision Guide: Choose if: the vessel uses a medium‑speed diesel propulsion system, operates in coastal or shallow water where robust bearing protection against sand and silt is required, and you have capacity for routine oil‑analysis and seal monitoring. Avoid if: the ship demands high‑speed low‑friction bearings, has very tight budget constraints, or lacks regular maintenance capability for seal inspection.
Use Cases: Installed on the stern tube of merchant ships ranging from ~5 000 to 30 000 DWT, typically in vessels with single screw propulsion where a reliable, low‑maintenance bearing is needed to transmit torque and keep water out of the oil system.
TMPB 0.25, 0.5, 1, 2.5, 5, 10, TMPB 0.25/A, 0.5/A, 1/A, 2.5/A, 5/A, 10/A, TMPB 0.251/A, 0.51/A, 1.01/A
Per propulsion shaft design
· Propulsion Shaft Line
· oil‑lubricated tapered roller bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- High load capacity across a wide size range (0.25–10 in.)
- Modular design with interchangeable seal kits for easy installation and replacement
- Proven DNV approval and long‑track record of reliability in marine propulsion
- Corrosion‑resistant steel alloys suitable for seawater exposure
- Low friction operation reduces shaft power loss
Weaknesses
- Higher initial cost compared with generic bearing options
- Requires precise alignment and regular oil quality monitoring to avoid seal leakage
- Performance can be affected by abrasive particles in coastal or shallow‑water operations
- Limited speed rating; not ideal for very high‑speed craft
- Maintenance interval (oil analysis, seal inspection) adds operational overhead
Typical Vessels:
TankerBulk CarrierContainer ShipOffshore Supply VesselCruise ShipLNG/LPG Carrier
Certifications:
DNV
Decision Guide: Choose if you need a robust, DNV‑approved stern tube bearing for medium to large vessels with conventional shaft speeds and can commit to regular oil analysis and seal inspections. Avoid if budget constraints are critical, the vessel operates at very high shaft RPMs, or the operating environment is extremely abrasive without adequate filtration.
Use Cases: Installed in the stern tube assembly of marine propulsion systems to support the propeller shaft, maintain alignment, and keep the bearing lubricated while preventing seawater ingress. Common on ships where reliable shaft line performance and compliance with classification societies are mandatory.
TPW-S, TPW-L
Per propulsion shaft design
· Propulsion Shaft Line
· Oil-lubricated stern tube bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Robust steel alloy construction with high load capacity
- Integrated oil seal reduces external leakage risk when properly maintained
- Standardised dimensions allow quick replacement during dockings
- Compatible with SKF condition‑monitoring sensors for predictive maintenance
- Class‑approved (DNV) and widely used in commercial fleets
Weaknesses
- Seal wear can lead to oil loss and marine pollution if not inspected daily
- Abrasive sand or silt in coastal/shallow water accelerates bearing wear
- Misalignment of the shaft causes uneven wear and premature failure
- Higher upfront cost compared with basic plain‑bearing solutions
- Requires regular oil analysis and alignment checks to maintain performance
Typical Vessels:
Bulk carrierTankerContainer shipRo‑Ro ferryOffshore supply vessel
Certifications:
DNV
Decision Guide: Choose if you need a proven, class‑approved stern tube bearing with integrated sealing and condition‑monitoring compatibility for low‑ to medium‑speed propulsion shafts. Avoid if the vessel operates primarily in high‑sand or silt environments without adequate filtration, or when budget constraints preclude regular seal and oil‑analysis maintenance.
Use Cases: Installed in the stern tube of commercial vessels that operate on oceanic routes as well as coastal trades, providing reliable shaft support for propeller shafts where continuous lubrication and easy access for inspection are required.
Tunnel Bearings and Plummer Blocks
Per propulsion shaft design
· Propulsion Shaft Line
· Tunnel bearing
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: SKF Marine GmbH: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- High radial and axial load capacity suitable for large propulsion shafts
- Modular plummer block design simplifies installation and maintenance
- Integrated sealing system reduces risk of oil leakage into the sea
- Proven DNV approval ensures compliance with classification society standards
- Low friction operation contributes to fuel efficiency
Weaknesses
- Sensitive to abrasive particles (sand, silt) in coastal or shallow‑water service unless extra filtration is used
- Requires regular seal inspection and oil analysis to prevent leakage and wear
- Higher upfront cost compared with basic plain bearings
- Limited size range; very large shafts may need custom solutions
- Precise alignment is critical – misalignment leads to uneven wear
Typical Vessels:
TankerBulk CarrierContainer ShipCruise VesselOffshore Supply Vessel
Certifications:
DNV
Decision Guide: Choose if the vessel operates primarily in open‑water conditions, demands high shaft load capacity, and requires a reliable sealed bearing system with proven classification approval. Avoid if the ship frequently runs in sand‑laden coastal or riverine waters without additional filtration, or if budget constraints preclude the higher initial investment.
Use Cases: Installed as part of the stern tube assembly on main propulsion lines of ocean‑going vessels, providing shaft support, thrust bearing function and oil containment for the propeller shaft. Commonly found in new builds and retrofits where long‑term reliability and compliance with classification society standards are priorities.
Thordon Marine
8
SXL Bearing
Per propulsion shaft design
· Seawater-lubricated
· Water-lubricated polymer
Common Failures & Inspection Points
- Misalignment or foundation movement causes vibration, bearing load changes and abnormal temperature
- Bearing, bush or coupling wear causes noise, vibration, backlash or rising temperature
- Seal deterioration causes lubricating-oil leakage or seawater ingress
- Lubrication contamination or low supply damages bearings and produces temperature or pressure alarms
- Control or hydraulic faults on controllable-pitch or PTO equipment cause incorrect response, alarms or loss of function
Service: Inspect alignment references, bearings, seals, couplings, lubrication, vibration and leakage. Review oil condition and bearing-temperature trends and check for shaft movement or abnormal wear. Test pitch, clutch or PTO controls under the approved procedure where applicable. Refer to manufacturer and class documentation for the exact figure for alignment, clearances and wear limits.
Spare Parts: Carry seals, filters, approved lubricants, coupling elements, bearing or bush service parts where practical, hydraulic-control spares and critical sensors.
Strengths
- Eliminates oil pollution risk
- Reduced maintenance due to water-lubrication
- Compliant with environmental regulations
- Increased durability and resistance to wear
- Easy to measure wear during drydock
Weaknesses
- Bearing wear beyond class limit can occur
- Scoring from debris is a potential issue
- Misalignment wear pattern can be a problem
- May require more frequent inspections
- Higher upfront cost compared to traditional bearings
Typical Vessels:
ContainerBulk CarrierTankerCruise ShipFerry
Certifications:
IMODNVABS
Decision Guide: Choose if you prioritize environmental compliance and reduced maintenance. Avoid if you are looking for a low upfront cost solution or have limited experience with water-lubricated bearings.
Use Cases: Conventional shaft propulsion, controllable-pitch propellers and shaft-driven electrical or mechanical auxiliaries.
Thordon SXL 200
unverified
· water-lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
200 mm
Material
SXL polymer
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or loss of bearing material increases shaft movement and is noticed as vibration, noise or abnormal clearance during inspection
- Poor lubrication or restricted water flow on water-lubricated designs causes heating, scoring or accelerated wear
- Misalignment or shaft deflection creates uneven loading and produces localized wear, elevated temperature or vibration
- Abrasive contamination or debris damages the bearing surface and causes scoring or rapid clearance growth
- Corrosion, delamination or material damage causes visible deterioration and may lead to unstable shaft support
Service: Inspect bearing condition, lubrication or flushing arrangement, shaft surface, alignment indicators and any accessible wear measurements. Trend stern-tube or bearing temperature and vibration where instrumentation is fitted. Investigate asymmetric wear because it can indicate shaft-line alignment problems rather than simple bearing age. Refer to the manufacturer and class documentation for the exact figure for clearance, wear and replacement limits.
Spare Parts: Carry manufacturer-approved bearing segments or a replacement bearing where vessel criticality justifies it, together with seals, approved lubricants or flushing-system service parts appropriate to the installation.
Strengths
- Corrosion‑resistant polymer eliminates need for oil lubrication and reduces environmental contamination risk.
- Low friction coefficient provides efficient power transmission and can extend propeller life.
- Long service intervals; the bearing material tolerates marine fouling without frequent maintenance.
- Lightweight compared with traditional bronze bearings, easing installation and reducing overall stern tube weight.
- Standardized dimensions allow straightforward fit on most 200 mm shaft arrangements.
Weaknesses
- Higher upfront cost than conventional metal (bronze) bearings.
- Maximum operating temperature is lower; excessive heat can accelerate polymer wear.
- Requires precise alignment and clean water flow; poor installation can lead to premature failure.
- Not ideal for very high‑power shafts where metal bearings may offer greater load capacity.
- Limited availability of spare parts in remote ports compared with more common bearing types.
Typical Vessels:
Bulk CarrierProduct TankerContainer ShipOffshore Supply VesselRo‑Ro Ferry
Decision Guide: Choose if you need an oil‑free, low‑maintenance bearing for shafts up to 200 mm on vessels operating in corrosive or environmentally sensitive waters. Avoid if the propulsion system exceeds the load/temperature limits of polymer bearings or if cost sensitivity outweighs long‑term maintenance savings.
Use Cases: Main propulsion shaft lines on merchant, passenger, offshore and work vessels.
Thordon SXL 300
unverified
· water-lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
300 mm
Material
SXL polymer
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or loss of bearing material increases shaft movement and is noticed as vibration, noise or abnormal clearance during inspection
- Poor lubrication or restricted water flow on water-lubricated designs causes heating, scoring or accelerated wear
- Misalignment or shaft deflection creates uneven loading and produces localized wear, elevated temperature or vibration
- Abrasive contamination or debris damages the bearing surface and causes scoring or rapid clearance growth
- Corrosion, delamination or material damage causes visible deterioration and may lead to unstable shaft support
Service: Inspect bearing condition, lubrication or flushing arrangement, shaft surface, alignment indicators and any accessible wear measurements. Trend stern-tube or bearing temperature and vibration where instrumentation is fitted. Investigate asymmetric wear because it can indicate shaft-line alignment problems rather than simple bearing age. Refer to the manufacturer and class documentation for the exact figure for clearance, wear and replacement limits.
Spare Parts: Carry manufacturer-approved bearing segments or a replacement bearing where vessel criticality justifies it, together with seals, approved lubricants or flushing-system service parts appropriate to the installation.
Strengths
- Eliminates the need for an oil lubrication system, reducing maintenance and environmental spill risk
- SXL polymer construction offers excellent corrosion resistance and low wear in seawater
- Optimised geometry for a 300 mm shaft provides compact installation and easy alignment
- Operates at lower temperatures than metal bearings, improving bearing life under normal loads
- Reduced noise and vibration compared with traditional bronze bearings
Weaknesses
- Lower load‑capacity limit than conventional bronze or babbitt bearings, restricting use on high‑power vessels
- Higher sensitivity to particulate contamination in the cooling water, requiring effective filtration
- Potentially higher upfront cost versus standard metal stern tube bearings
- Limited documented classification approvals; some societies may require additional testing
- Polymer material can degrade if exposed to excessive temperatures or aggressive chemicals
Typical Vessels:
Product TankerGeneral Cargo ShipOffshore Supply VesselFerrySmall Bulk Carrier
Decision Guide: Choose if you need an oil‑free, low‑maintenance bearing for a medium‑size shaft and operate in clean seawater environments where corrosion resistance is critical. Avoid if the vessel requires high thrust loads, operates with significant waterborne debris, or must meet strict classification approvals that currently lack documented acceptance of this polymer design.
Use Cases: Main propulsion shaft lines on merchant, passenger, offshore and work vessels.
Thordon SXL 400
unverified
· water-lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
400 mm
Material
SXL polymer
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or lubrication loss can raise temperature and vibration, noticed through monitoring or abnormal noise
- Misalignment can produce uneven bearing loads, vibration and accelerated seal wear
- Seal deterioration can cause oil leakage or seawater ingress, seen in stern-tube levels or bilges
- Corrosion or fretting at interfaces can damage shafts, sleeves or bearing housings
- Loose foundations or damaged chocking can shift alignment and change vibration behavior
Service: Trend bearing temperatures, vibration, lubricant condition and seal leakage and inspect foundations and accessible shaft surfaces. Check alignment indicators after major repair or grounding events as required by vessel procedures. Clearances, wear-down limits and alignment tolerances must be taken from class-approved and manufacturer documentation.
Spare Parts: Carry approved seal elements, O-rings, bearing service parts, lubricant filters and maker-recommended monitoring sensors or fittings.
Strengths
- Oil‑free operation eliminates the need for an oil lubrication system
- Corrosion‑resistant polymer material reduces maintenance in seawater environments
- Lightweight compared with traditional bronze bearings, lowering overall propeller assembly mass
- Low friction coefficient improves propulsion efficiency
Weaknesses
- Generally lower load capacity than metal (bronze) bearings, limiting use on very high‑power shafts
- Polymer may be more susceptible to wear under abrasive water conditions if water quality is poor
- Limited long‑term field data compared with established metal bearing types
- Replacement intervals may be shorter in high‑stress applications
Typical Vessels:
Bulk CarrierContainer ShipTankerGeneral Cargo
Decision Guide: Choose if you need an oil‑free, corrosion‑resistant bearing for a 400 mm shaft on vessels where weight savings and reduced maintenance are priorities. Avoid if the propulsion system requires very high torque or operates under abrasive water conditions that exceed polymer wear limits.
Use Cases: Used in conventional shaft-line propulsion installations on merchant, passenger, naval and offshore vessels.
Thordon SXL 500
unverified
· water‑lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
500 mm
Material
SXL polymer
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or lubrication loss can raise temperature and vibration, noticed through monitoring or abnormal noise
- Misalignment can produce uneven bearing loads, vibration and accelerated seal wear
- Seal deterioration can cause oil leakage or seawater ingress, seen in stern-tube levels or bilges
- Corrosion or fretting at interfaces can damage shafts, sleeves or bearing housings
- Loose foundations or damaged chocking can shift alignment and change vibration behavior
Service: Trend bearing temperatures, vibration, lubricant condition and seal leakage and inspect foundations and accessible shaft surfaces. Check alignment indicators after major repair or grounding events as required by vessel procedures. Clearances, wear-down limits and alignment tolerances must be taken from class-approved and manufacturer documentation.
Spare Parts: Carry approved seal elements, O-rings, bearing service parts, lubricant filters and maker-recommended monitoring sensors or fittings.
Strengths
- Eliminates the need for oil lubrication system, reducing maintenance and environmental risk
- Corrosion‑resistant polymer material provides long service life in seawater exposure
- Low friction coefficient improves propeller efficiency and reduces shaft wear
- Simplified installation with fewer ancillary components
Weaknesses
- Maximum load rating lower than high‑performance oil‑lubricated bearings, limiting use on very high‑power vessels
- Polymer material may be sensitive to extreme temperature excursions beyond design limits
- Limited proven track record compared with legacy bearing manufacturers
- Potential for higher wear rates if water quality (e.g., debris, biofouling) is not adequately controlled
Typical Vessels:
Bulk CarrierTankerContainer ShipGeneral Cargo VesselCruise Ship (mid‑size)
Decision Guide: Choose if: you need a low‑maintenance, oil‑free bearing for vessels up to medium power where corrosion resistance and simplicity are priorities. Avoid if: the propulsion system operates at very high shaft loads or speeds, or if the vessel requires a bearing with proven extreme‑pressure performance under harsh temperature conditions.
Use Cases: Used in conventional shaft-line propulsion installations on merchant, passenger, naval and offshore vessels.
Thordon ThorPlas-Blue 200
unverified
· water-lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
200 mm
Material
ThorPlas-Blue
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or lubrication loss can raise temperature and vibration, noticed through monitoring or abnormal noise
- Misalignment can produce uneven bearing loads, vibration and accelerated seal wear
- Seal deterioration can cause oil leakage or seawater ingress, seen in stern-tube levels or bilges
- Corrosion or fretting at interfaces can damage shafts, sleeves or bearing housings
- Loose foundations or damaged chocking can shift alignment and change vibration behavior
Service: Trend bearing temperatures, vibration, lubricant condition and seal leakage and inspect foundations and accessible shaft surfaces. Check alignment indicators after major repair or grounding events as required by vessel procedures. Clearances, wear-down limits and alignment tolerances must be taken from class-approved and manufacturer documentation.
Spare Parts: Carry approved seal elements, O-rings, bearing service parts, lubricant filters and maker-recommended monitoring sensors or fittings.
Strengths
- Eliminates oil sump and associated maintenance, reducing environmental risk.
- ThorPlas‑Blue material provides excellent corrosion resistance in seawater.
- Lightweight compared with traditional bronze bearings, lowering shaft line mass.
- Standard dimensions fit common 200 mm shafts, simplifying installation.
Weaknesses
- Lower load and thrust capacity than metal (bronze) bearings; unsuitable for high‑power main engines.
- Polymer material has temperature limits (~80 °C), restricting use in high‑speed or hot‑water environments.
- Performance depends on continuous, clean water flow; blockage can cause rapid wear.
- Less extensive long‑term field history than legacy bearing designs.
Decision Guide: Choose if the vessel operates with moderate power (typically <5 MW), uses a 200 mm shaft, and seeks to avoid oil‑lubricated bearings for maintenance or environmental reasons. Avoid on high‑thrust, high‑speed ships or where water flow cannot be guaranteed.
Use Cases: Used in conventional shaft-line propulsion installations on merchant, passenger, naval and offshore vessels.
Thordon ThorPlas-Blue 300
unverified
· water‑lubricated polymer stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
300 mm
Material
ThorPlas-Blue
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or loss of bearing material increases shaft movement and is noticed as vibration, noise or abnormal clearance during inspection
- Poor lubrication or restricted water flow on water-lubricated designs causes heating, scoring or accelerated wear
- Misalignment or shaft deflection creates uneven loading and produces localized wear, elevated temperature or vibration
- Abrasive contamination or debris damages the bearing surface and causes scoring or rapid clearance growth
- Corrosion, delamination or material damage causes visible deterioration and may lead to unstable shaft support
Service: Inspect bearing condition, lubrication or flushing arrangement, shaft surface, alignment indicators and any accessible wear measurements. Trend stern-tube or bearing temperature and vibration where instrumentation is fitted. Investigate asymmetric wear because it can indicate shaft-line alignment problems rather than simple bearing age. Refer to the manufacturer and class documentation for the exact figure for clearance, wear and replacement limits.
Spare Parts: Carry manufacturer-approved bearing segments or a replacement bearing where vessel criticality justifies it, together with seals, approved lubricants or flushing-system service parts appropriate to the installation.
Strengths
- Eliminates oil leakage risk – fully water lubricated
- Corrosion‑resistant polymer material reduces maintenance intervals
- Quiet operation compared with metal bearings
- Direct fit for standard 300 mm shafts, simplifying installation
- Lower environmental impact – no oil handling or disposal
Weaknesses
- Load capacity lower than conventional oil‑lubricated bronze/steel bearings
- Performance can degrade in low cooling‑water flow or high‑temperature conditions
- Not recommended for very high‑power main engines (>10 MW) or heavy‑duty applications
- Requires precise alignment during installation to avoid premature wear
Typical Vessels:
Bulk CarrierContainer ShipTankerOffshore Supply VesselFerryGeneral Cargo
Decision Guide: Choose if: the vessel operates in warm waters with reliable cooling‑water flow, seeks to minimise oil handling and maintenance costs, and has a shaft power within the rating of water‑lubricated polymer bearings. Avoid if: the propulsion system demands very high torque or operates under extreme temperature/low‑flow conditions, or where class societies mandate oil‑lubricated bearings.
Use Cases: Main propulsion shaft lines on merchant, passenger, offshore and work vessels.
Thordon ThorPlas-Blue 400
unverified
· water-lubricated stern tube bearing
Bearing type
water-lubricated stern tube bearing
Shaft diameter
400 mm
Material
ThorPlas-Blue
Application
marine stern tube bearing
Common Failures & Inspection Points
- Bearing wear or loss of bearing material increases shaft movement and is noticed as vibration, noise or abnormal clearance during inspection
- Poor lubrication or restricted water flow on water-lubricated designs causes heating, scoring or accelerated wear
- Misalignment or shaft deflection creates uneven loading and produces localized wear, elevated temperature or vibration
- Abrasive contamination or debris damages the bearing surface and causes scoring or rapid clearance growth
- Corrosion, delamination or material damage causes visible deterioration and may lead to unstable shaft support
Service: Inspect bearing condition, lubrication or flushing arrangement, shaft surface, alignment indicators and any accessible wear measurements. Trend stern-tube or bearing temperature and vibration where instrumentation is fitted. Investigate asymmetric wear because it can indicate shaft-line alignment problems rather than simple bearing age. Refer to the manufacturer and class documentation for the exact figure for clearance, wear and replacement limits.
Spare Parts: Carry manufacturer-approved bearing segments or a replacement bearing where vessel criticality justifies it, together with seals, approved lubricants or flushing-system service parts appropriate to the installation.
Strengths
- Corrosion‑resistant polymer material reduces wear in seawater environments
- Eliminates the need for an oil lubrication system, saving space and maintenance effort
- Designed specifically for 400 mm shafts common on medium‑speed vessels
- Lower weight than traditional cast‑iron or babbitt bearings, easing installation
- Fits standard stern tube housings without major modifications
Weaknesses
- Load capacity generally lower than high‑performance oil‑lubricated bearings
- Performance can be sensitive to water quality and temperature extremes
- May require more frequent inspection in very high‑power applications
- Limited long‑term field data compared with legacy bearing manufacturers
- Not suitable for shafts larger than 400 mm without redesign
Typical Vessels:
Bulk CarrierTankerContainer ShipGeneral Cargo VesselRo-Ro
Decision Guide: Choose if you need a low‑maintenance, corrosion‑resistant bearing for a 400 mm shaft and prefer water lubrication to avoid oil systems. Avoid on very high‑power or heavy‑load ships where maximum load capacity is critical, or when operating in waters with poor quality that could affect bearing performance.
Use Cases: Main propulsion shaft lines on merchant, passenger, offshore and work vessels.
Wärtsilä
3
Johnson Cutless Bearing
Shaft diameter 25-750 mm
· Seawater lubricated
· Water‑lubricated cutless stern tube bearing
Type
Water-Lubricated Stern Tube / Strut Bearing (Rubber)
Size Range
- Cutless 400
- Cutless 500
- Cutless 700 HP
Drive Type
Passive (seawater lubricated)
Construction
Nitrile rubber staves in bronze or non-metallic shell
Common Failures & Inspection Points
- Rubber stave wear from sand/debris ingestion
- Rubber delamination from age/UV exposure (above waterline bearings)
- Shell corrosion (bronze — dezincification in stagnant seawater)
Service: Bearing clearance measurement at drydock. Typical life 5-15 years depending on operating conditions. Replacement at drydock when clearance exceeds Class limits.
Spare Parts: Duramax Marine (Cleveland, OH, now part of Wärtsilä). Standard sizes widely stocked. Lead time: 1-3 weeks for standard, 4-8 weeks for custom sizes.
Strengths
- No oil contamination risk – fully water lubricated
- Cutless design simplifies installation and removal, reducing dry‑dock time
- Low routine maintenance; no oil change or seal replacement required
- Effective sealing against external water ingress, protecting the shaft journal
- Proven performance for power ranges up to 700 HP (suitable for many medium‑size vessels)
Weaknesses
- Rubber staves are susceptible to wear from sand, debris or abrasive particles in cooling water
- Ageing and UV exposure can cause rubber delamination, especially on above‑waterline installations
- Bronze shells may suffer dezincification or corrosion if water flow is stagnant
- Limited to lower power ranges compared with high‑power oil‑lubricated bearings
- Requires regular clearance checks at dry‑dock; life typically 5–15 years
Typical Vessels:
Bulk CarrierTankerContainer ShipGeneral Cargo VesselOffshore Supply VesselFerry
Certifications:
DNV GLABSLloyd's Register
Decision Guide: Choose if: you need a low‑maintenance, oil‑free stern tube for vessels up to ~700 HP, operating in clean cooling water and prefer reduced dry‑dock turnaround. Avoid if: the ship operates in high‑debris or sand‑laden waters, requires very high power transmission, or the bearing will be exposed above the waterline without UV protection.
Use Cases: Johnson Cutless Bearings are commonly installed on medium‑size merchant ships (tanker, bulk carrier, container) and offshore support vessels where a compact, oil‑free stern tube reduces environmental risk and maintenance workload. They are favoured in fleets that schedule regular dry‑dock inspections to monitor bearing clearance.
Wartsila Stern Tube Seal (Lip Seal)
Shaft diameter 150-1,200 mm
· Seawater / Stern Tube Oil interface
· Passive lip seal with air/oil barrier
Type
Stern Tube Seal (Lip Seal / Face Seal)
Size Range
- Airguard
- Enviroguard
- FSTL
- FST
Drive Type
Passive
Construction
Multi-lip rubber seal rings with air/oil barrier
Common Failures & Inspection Points
- Lip seal wear from shaft roughness/scoring — primary oil loss cause
- Seal ring hardening from age (rubber degradation after 10-15 years)
- Shaft liner scoring from debris trapped under seal lips
- Air supply system failure on Airguard models causing oil loss
Service: Seal drain inspection daily. Air supply pressure check daily (Airguard). Oil consumption monitoring — abnormal increase indicates seal wear. Seal replacement at drydock (every 5-10 years or as needed). Shaft liner condition check at each seal replacement.
Spare Parts: Wärtsilä Seals & Bearings (ehem. Cedervall, Gothenburg). Seal kits: 4-8 weeks lead time. Keep onboard: spare seal elements for emergency replacement afloat (limited repair possible).
Strengths
- Proven design in service since the 1960s, widely accepted by classification societies
- Simple passive operation – no external drive required
- Airguard variant provides an active pressurised air barrier that reduces oil loss
- Straight‑forward daily inspection (drain check and air pressure verification)
- Available in several size families (Airguard, Enviroguard, FSTL, FST) to match a range of shaft diameters
Weaknesses
- Seal wear accelerates if the shaft surface is rough or scored
- Rubber hardening after 10‑15 years necessitates scheduled replacement
- Air supply system for Airguard models adds complexity; failure can cause rapid oil loss
- Not ideal for very high shaft speeds (>200 rpm) where heat buildup may exceed seal limits
- Replacement generally requires dry‑dock, leading to planned downtime
Typical Vessels:
Bulk CarrierContainer ShipTankerGeneral Cargo VesselRo‑Ro
Certifications:
DNV
Decision Guide: Choose if you need a reliable, low‑maintenance seal for conventional shaft lines and can perform regular air pressure checks or accept scheduled dry‑dock replacement. Avoid if the vessel operates at very high shaft speeds, requires rapid on‑board seal change without dry‑dock, or cannot guarantee continuous air supply to an Airguard system.
Use Cases: Standard stern tube bearing protection on mid‑size merchant vessels (10–150 m) where a passive seal is preferred; commonly installed in new builds and retrofits for bulk carriers, tankers, and container ships operating at moderate shaft speeds.
Oil-Lubricated White Metal
Per propulsion shaft design
· Lube Oil
· oil‑lubricated white metal bearing
Common Failures & Inspection Points
- Misalignment or foundation movement causes vibration, bearing load changes and abnormal temperature
- Bearing, bush or coupling wear causes noise, vibration, backlash or rising temperature
- Seal deterioration causes lubricating-oil leakage or seawater ingress
- Lubrication contamination or low supply damages bearings and produces temperature or pressure alarms
- Control or hydraulic faults on controllable-pitch or PTO equipment cause incorrect response, alarms or loss of function
Service: Inspect alignment references, bearings, seals, couplings, lubrication, vibration and leakage. Review oil condition and bearing-temperature trends and check for shaft movement or abnormal wear. Test pitch, clutch or PTO controls under the approved procedure where applicable. Refer to manufacturer and class documentation for the exact figure for alignment, clearances and wear limits.
Spare Parts: Carry seals, filters, approved lubricants, coupling elements, bearing or bush service parts where practical, hydraulic-control spares and critical sensors.
Strengths
- Proven, long‑standing technology with extensive field experience
- High load capacity for medium‑speed shafts (up to ~20 000 kW)
- Simple oil lubrication system – compatible with existing shipboard lubricating plants
- Easy replacement and overhaul procedures
- Integrated temperature sensor enables real‑time condition monitoring
Weaknesses
- Susceptible to white‑metal fatigue cracking if oil flow is interrupted
- Requires strict oil cleanliness and continuous supply; oil starvation leads to rapid damage
- Higher maintenance interval compared with foil or polymer bearings
- Temperature alarms can be triggered by normal load spikes, leading to false positives
- Not optimal for very high‑speed or ultra‑low‑vibration applications
Typical Vessels:
Bulk CarrierProduct TankerGeneral CargoContainer Ship (up to mid‑size)Ro‑Ro / Ferry
Certifications:
DNV GL approvedABS class approvalLR (Lloyd’s Register) approved
Decision Guide: Choose if: you operate a conventional medium‑speed vessel with an existing oil lubrication system, need a cost‑effective, well‑understood bearing and have robust temperature monitoring. Avoid if: the shaft runs at very high RPM, you require ultra‑low maintenance intervals, or you prefer oil‑free solutions for reduced environmental risk.
Use Cases: Conventional shaft propulsion, controllable-pitch propellers and shaft-driven electrical or mechanical auxiliaries.
Aegir Marine (Netherlands)
1
Oil-Free Stern Tube System
Shaft diameter 200-1,000 mm
· Seawater lubricated (zero oil to sea)
· Seawater‑lubricated polymer stern tube
Type
Complete Oil-Free Stern Tube System (Bearing + Seal)
Size Range
- AOFS-200
- AOFS-400
- AOFS-600
- AOFS-800
Drive Type
Passive (seawater lubricated)
Construction
Polymer bearing + face seal, complete system, no oil
Common Failures & Inspection Points
- Face seal wear from debris in seawater
- Polymer bearing wear in silty waters
- System air entrapment causing bearing noise
Service: Bearing clearance check at drydock. Face seal inspection at drydock. Seawater supply system filter check monthly. Zero oil consumption — no oil monitoring needed.
Spare Parts: Aegir Marine (Heerhugowaard, Netherlands). Lead time: 4-8 weeks. Complete system engineering for retrofit available.
Strengths
- Zero oil handling – no risk of oil leakage or MARPOL Annex I violations
- Reduced routine maintenance (no oil changes, simpler dry‑dock checks)
- Passive seawater lubrication lowers power loss compared with oil‑circulated systems
- Modular size range (AOFS‑200 to AOFS‑800) fits a variety of shaft diameters
- Simplified environmental compliance and lower operating cost
Weaknesses
- Face seal wear accelerated by debris or marine growth in the seawater stream
- Polymer bearing wear can increase in silty or high‑particulate water conditions
- Air entrapment may cause audible bearing noise if filtration is inadequate
- Requires a reliable seawater supply and regular filter maintenance
- Load capacity lower than some traditional metal‑on‑metal stern tubes, limiting use on very high‑power vessels
Typical Vessels:
Product tankerChemical carrierLNG/LPG carrierOffshore supply vesselContainer ship (mid‑size)Cruise liner (retrofit)
Decision Guide: Choose if you need an oil‑free solution to meet strict environmental regulations, want lower routine maintenance and have a clean seawater filtration system. Avoid on vessels operating in highly silty or debris‑laden waters, or where the required thrust exceeds the polymer bearing’s design limits.
Use Cases: Commonly installed on new builds of product and chemical tankers to eliminate oil handling, and retrofitted during dry‑dock periods on offshore supply ships and cruise vessels seeking to reduce environmental risk and maintenance costs. Ideal for routes with good seawater quality and where compliance with MARPOL Annex I is a priority.
Blohm+Voss / Aegir Marine (Germany/Netherlands)
1
White Metal Stern Tube Bearing
Shaft diameter 150-1,000 mm
· Oil lubricated
· oil‑lubricated white‑metal bearing
Type
Oil-Lubricated Stern Tube Bearing (White Metal / Babbitt)
Size Range
- WM-150
- WM-300
- WM-500
- WM-700
- WM-1000
Drive Type
Passive (oil lubricated via stern tube oil system)
Construction
White metal (tin-based Babbitt) cast in bronze or steel housing
Common Failures & Inspection Points
- White metal wiping from shaft misalignment or sudden load
- Oil contamination from seawater ingress past stern tube seal
- Oil loss to sea from seal failure — MARPOL environmental concern
- Bearing temperature rise from oil degradation
Service: Stern tube oil level/quality check daily. Oil temperature monitoring continuous. Oil analysis every 3 months. Bearing clearance measurement at drydock. White metal re-casting if wiped — specialized shore facility.
Spare Parts: Multiple manufacturers (Aegir Marine Netherlands, Blohm+Voss Germany, local foundries). White metal re-pour: 1-3 weeks at specialized facility. Emergency repair at drydock.
Strengths
- Proven design dating back to early 1900s with extensive service history in merchant fleets.
- High static and dynamic load capacity suitable for medium‑to‑high power shafts.
- Compatible with standard stern‑tube oil systems; no need for special lubricants or cooling equipment.
- White‑metal can be re‑cast on‑shore, allowing repair of wiped bearings without full replacement.
- Widely stocked by Blohm+Voss/Aegir Marine, facilitating quick procurement and spare‑part availability.
Weaknesses
- Requires precise shaft alignment; misalignment leads to rapid white‑metal wear or wiping.
- Sensitive to oil contamination (water ingress, particles) which can cause overheating and premature failure.
- Heavier and bulkier than modern polymer or composite bearings, affecting installation space.
- Environmental risk: oil loss through seal failure results in MARPOL‑regulated discharge.
- Maintenance intensive – daily oil level/quality checks, continuous temperature monitoring, quarterly oil analysis.
Typical Vessels:
Product TankerBulk CarrierContainer ShipCruise VesselOffshore Supply Vessel
Certifications:
DNVABSLR
Decision Guide: Choose if the vessel already uses a conventional oil‑lubricated stern tube, needs a robust bearing with high load capacity, and values proven long‑term service experience. Avoid if the ship operator prefers low‑maintenance polymer bearings, operates in extreme temperature or highly corrosive environments, or has strict zero‑oil‑leak policies.
Use Cases: Installed on new builds and retrofits of merchant ships where a traditional oil‑lubricated stern tube is specified; commonly used in dry‑dock overhauls to replace worn bearings or re‑cast white‑metal after wiping incidents.
Duramax Marine
1
DM Marine Bearing
Per propulsion shaft design
· Seawater-lubricated
· composite stave bearing
Common Failures & Inspection Points
- Misalignment or foundation movement causes vibration, bearing load changes and abnormal temperature
- Bearing, bush or coupling wear causes noise, vibration, backlash or rising temperature
- Seal deterioration causes lubricating-oil leakage or seawater ingress
- Lubrication contamination or low supply damages bearings and produces temperature or pressure alarms
- Control or hydraulic faults on controllable-pitch or PTO equipment cause incorrect response, alarms or loss of function
Service: Inspect alignment references, bearings, seals, couplings, lubrication, vibration and leakage. Review oil condition and bearing-temperature trends and check for shaft movement or abnormal wear. Test pitch, clutch or PTO controls under the approved procedure where applicable. Refer to manufacturer and class documentation for the exact figure for alignment, clearances and wear limits.
Spare Parts: Carry seals, filters, approved lubricants, coupling elements, bearing or bush service parts where practical, hydraulic-control spares and critical sensors.
Strengths
- Oil‑free operation eliminates lubrication leakage and reduces environmental impact
- Composite material provides excellent corrosion resistance in seawater
- Long service life with low routine maintenance requirements
- Reduced noise and vibration compared with traditional metal bearings
- Suitable for retrofits where existing oil‑lubricated bearings are being replaced
Weaknesses
- Higher upfront capital cost than conventional babbitt or bronze bearings
- Load capacity may be lower than heavy‑duty metal bearing designs
- Performance is sensitive to shaft misalignment; edge loading can accelerate wear
- Potential for damage from foreign objects entering the stern tube
- Requires careful installation and alignment procedures
Typical Vessels:
Bulk CarrierProduct TankerContainer ShipOffshore Supply VesselGeneral Cargo Vessel
Decision Guide: Choose if: you need a low‑maintenance, oil‑free bearing for medium‑speed propulsion shafts, operate in corrosive environments, or are pursuing greener vessel designs. Avoid if: the vessel demands very high shaft loads, budget constraints limit upfront spending, or alignment tolerances cannot be reliably met.
Use Cases: Conventional shaft propulsion, controllable-pitch propellers and shaft-driven electrical or mechanical auxiliaries.
Kamome Propeller (Japan)
1
KP Stern Tube System
Shaft diameter 150-700 mm
· Oil lubricated
· Passive oil‑lubricated white‑metal stern tube
Type
Complete Stern Tube System (Bearing + Seal + Oil System)
Size Range
- KP-150
- KP-300
- KP-500
- KP-700
Drive Type
Passive (oil lubricated)
Construction
White metal bearing, lip seal, gravity oil tank
Common Failures & Inspection Points
- White metal wiping from alignment issues
- Seal wear causing oil loss
- Oil tank level drop from seal leakage
Service: Stern tube oil level check daily. Oil analysis quarterly. Bearing clearance at drydock. Seal replacement at drydock.
Spare Parts: Kamome Propeller (Aioi, Japan). Lead time: 3-5 weeks Asia.
Strengths
- Integrated package (bearing, seal and oil tank) simplifies procurement and installation
- Passive gravity‑fed oil system eliminates the need for pumps or pressure regulators
- White‑metal bearing offers low friction and high load capacity for medium‑power shafts
- Modular size range (KP‑150 to KP‑700) fits a wide variety of vessel classes
- Simple daily oil‑level check and quarterly oil analysis support straightforward maintenance
Weaknesses
- White‑metal bearing is sensitive to misalignment; alignment errors can cause rapid wear
- Lip seal wear can lead to oil loss, requiring replacement at each dry‑dock
- Gravity oil tank limits oil capacity, which may be insufficient for very long voyages without frequent checks
- Passive lubrication provides less control over oil flow compared with active pressure systems on high‑power shafts
- No built‑in condition‑monitoring sensors; relies on manual inspection
Typical Vessels:
Bulk CarrierContainer ShipTankerGeneral Cargo VesselOffshore Supply Vessel
Decision Guide: Choose if: you need a simple, low‑maintenance stern tube for medium‑size shafts (150–700 mm) where passive oil lubrication is acceptable and installation simplicity is valued. Avoid if: the vessel operates at high shaft power or speed, requires active pressure lubrication, has strict alignment tolerances, or needs integrated condition‑monitoring electronics.
Use Cases: Commonly installed on new‑builds or retrofits of medium‑size merchant ships and offshore support vessels during dry‑dock periods. Used where daily oil‑level checks are feasible and the operating profile does not demand high‑pressure lubrication systems.
Kobelco Eagle Marine (Japan)
1
KE Stern Tube Seal
Shaft diameter 150-800 mm
· Seawater / Stern Tube Oil interface
· Passive multi‑lip stern tube seal
Type
Stern Tube Seal (Lip Seal)
Size Range
- KE-150
- KE-300
- KE-500
- KE-800
Drive Type
Passive
Construction
Multi-lip rubber seal, chrome or ceramic shaft liner
Common Failures & Inspection Points
- Lip seal wear from shaft liner surface deterioration
- Oil consumption increase from worn aft seal
- Ceramic liner chipping (ceramic variants)
Service: Drain inspection daily. Seal replacement at drydock. Shaft liner inspection at seal change.
Spare Parts: Kobelco Eagle Marine (Kobe, Japan). Lead time: 3-5 weeks Asia, 6-10 weeks elsewhere.
Strengths
- Proven design lineage since 1975, widely used in commercial shipping
- Multi‑lip rubber construction provides reliable oil retention under normal operating pressures
- Optional ceramic liner offers higher wear resistance for abrasive shaft surfaces
- Simple passive drive – no external power or hydraulic actuation required
- Straightforward replacement during scheduled dry‑dock periods
Weaknesses
- Lip seal wear accelerates if the shaft liner surface deteriorates, leading to oil loss
- Ceramic liners can chip under impact or misalignment, requiring careful handling
- Oil consumption rises noticeably when aft lip becomes worn
- Limited to shaft diameters covered by KE‑150 – KE‑800 range; not suitable for very large or small shafts
- Requires daily drain inspection and periodic dry‑dock seal change – higher planned maintenance
Typical Vessels:
Bulk CarrierProduct TankerContainer ShipCruise VesselOffshore Support Vessel
Decision Guide: Choose if: the vessel uses a conventional low‑ to medium‑speed diesel engine with a standard stern tube bearing, you need a proven, easy‑to‑maintain seal and are comfortable with scheduled dry‑dock replacement. Avoid if: the propulsion system operates at high speeds or pressures that exceed passive lip‑seal capability, or if an active mechanical seal is required for tighter leakage tolerances.
Use Cases: Deployed on commercial cargo ships and passenger vessels to seal the main engine shaft where it exits the hull, protecting the bearing oil from seawater ingress and retaining lubrication during normal voyages. Commonly installed during new‑build outfitting or retrofitted during dry‑dock overhauls.
Kongsberg Maritime
1
Bearing Wear Sensor PSS11
Per propulsion shaft design
· Propulsion Shaft Line
· Bearing wear monitoring sensor
Common Failures & Inspection Points
- Shaft bearing wear during coastal/shallow water operation (sand/silt)
- Wellenabdichtung-Leckage verursacht Ölverlust ins Meer
- Propellerflügel-Kavitationserosion
- Wellenfluchtungs-Abweichung verursacht ungleichmäßigen Lagerverschleiß
Service: Bearing clearance measurement during docking. Shaft seal daily drain inspection. Oil analysis quarterly. Propeller inspection during docking.
Spare Parts: Kongsberg Maritime AS Avd Skonnertvegen: Hold seal elements and wear measurement tools on board. Lead time: 4–8 weeks.
Strengths
- Real‑time clearance measurement enables early detection of bearing wear before failure.
- Integrated with Kongsberg Condition Monitoring System for automated alarm thresholds.
- Robust marine‑grade housing suitable for harsh coastal and shallow‑water environments.
- DNV approved, providing recognised class society validation.
Weaknesses
- Limited to specific shaft diameters; retro‑fit on older vessels may require mechanical adaptation.
- Requires periodic calibration and verification during dry‑dock periods.
- Additional wiring and integration effort with existing ship monitoring networks.
- Higher upfront cost compared with simple manual clearance gauges.
Typical Vessels:
Coastal tankerOffshore supply vesselFerryContainer ship operating in shallow watersBulk carrier on riverine routes
Certifications:
DNV
Decision Guide: Choose the PSS11 if you need continuous, automated bearing wear monitoring for vessels that operate in sand‑laden or silt‑rich coastal and inland waters where premature stern‑tube wear is a known risk. Avoid it on ships that already have an approved condition‑monitoring system using a different sensor type, or when budget constraints preclude the additional integration work.
Use Cases: The PSS11 is typically installed on the stern tube of vessels navigating coastal, riverine or shallow‑water routes where abrasive particles accelerate bearing wear. It supports predictive maintenance programmes by providing early warning of clearance growth, allowing planned dry‑dock interventions rather than unplanned failures.
Micromatic (Italy)
1
MM Stern Tube Bearing
Shaft diameter 100-800 mm
· Oil lubricated / Water lubricated
Type
Stern Tube Bearing (White Metal / Polymer)
Size Range
- MM-100
- MM-300
- MM-500
- MM-800
Drive Type
Passive
Construction
White metal or polymer in bronze housing
Common Failures & Inspection Points
- White metal wiping from misalignment
- Polymer wear from debris ingestion (water-lubricated)
- Housing fit loosening from vibration
Service: Per bearing type. Oil-lubricated: oil analysis quarterly. Water-lubricated: clearance check at drydock.
Spare Parts: Micromatic (Genova, Italy). Lead time: 4-6 weeks.
Strengths
- Proven design lineage since 1985 with extensive field experience
- Two material options (white metal and polymer) allow selection between oil‑lubricated and water‑lubricated operation
- Standardised size range (MM‑100 to MM‑800) fits most low‑speed merchant shafts
- Robust bronze housing provides good resistance to corrosion and vibration
- Simple passive thrust design eases installation and reduces auxiliary system complexity
Weaknesses
- White‑metal bearings are vulnerable to wiping if shaft alignment is poor
- Polymer bearings can experience accelerated wear when debris or sand enters the water‑lubricated circuit
- Requires regular clearance checks at dry‑dock for water‑lubricated units
- Not suited for very high thrust or high‑speed applications where active thrust control is required
- Limited to passive drive; no integrated thrust compensation mechanisms
Typical Vessels:
Bulk CarrierProduct TankerContainer ShipGeneral Cargo VesselOffshore Supply VesselFerry
Certifications:
DNV
Decision Guide: Choose if: you need a reliable, low‑maintenance bearing for conventional low‑speed diesel propulsion, want the flexibility of oil or water lubrication, and your shaft size falls within the MM‑100 to MM‑800 range. Avoid if: the vessel operates with high thrust loads, requires active thrust compensation, or runs in environments with heavy particulate ingress that could damage polymer liners.
Use Cases: Typically installed in the stern tube of merchant vessels built from the late 1990s onward, both new builds and retrofits, where a standardised passive thrust bearing is required. Commonly used on ships with shaft powers up to several thousand kilowatts and operating at propeller speeds below 150 rpm.
Orkot / Trelleborg (UK/Sweden)
1
TLM Marine Bearing
Shaft diameter 50-1,000 mm
· Water lubricated / Oil lubricated
· Composite polymer self‑lubricating bearing
Type
Composite Polymer Stern Tube Bearing
Size Range
- Orkot TLM
- Orkot TXMM
- Orkot C301
Drive Type
Passive
Construction
PTFE/polyester composite, self-lubricating
Common Failures & Inspection Points
- Wear from contaminated lubrication water
- Swelling from incompatible lubricant contact
- Edge loading from shaft misalignment
Service: Clearance check at drydock. Self-lubricating — less maintenance than white metal. Typical life 10-20 years. No oil pollution risk.
Spare Parts: Trelleborg Sealing Solutions (Rotherham, UK). Lead time: 3-6 weeks for standard sizes, 6-10 weeks for custom.
Strengths
- Self‑lubricating PTFE/polyester matrix eliminates the need for oil lubrication systems
- Long service life of 10–20 years reduces dry‑dock frequency
- Corrosion‑resistant and no risk of oil pollution in case of leakage
- Lightweight compared with metal bearings, easing installation
- Compatible with most class societies when installed per approved procedures
Weaknesses
- Higher upfront purchase price than conventional white‑metal bearings
- Limited size range; very large shafts may require alternative solutions
- Swelling or degradation if incompatible lubricants or chemicals are introduced
- Edge loading is critical – misaligned shafts can cause premature wear
- Bearing cannot be re‑machined; failure usually requires full replacement
Typical Vessels:
Bulk carrierProduct tankerContainer shipOffshore supply vesselCruise liner
Decision Guide: Choose if: you need a low‑maintenance, environmentally friendly bearing with long service intervals and class approval for new builds or retrofits. Avoid if: the project budget cannot accommodate the higher initial cost, the shaft size exceeds the TLM range, or the vessel operates under conditions that may introduce incompatible chemicals to the bearing.
Use Cases: Commonly installed in medium‑speed diesel propulsion systems on commercial cargo vessels and offshore support ships, especially where dry‑dock intervals are minimized and environmental regulations restrict oil leakage. Also favoured for retrofits on existing ships seeking to replace worn white‑metal bearings with a longer‑lasting solution.
SKF Marine (Sweden)
1
Simplex Compact Seal
Shaft diameter 100-1,200 mm
· Seawater / Stern Tube Oil interface
· Passive multi‑lip stern tube seal
Type
Stern Tube Seal (Lip Seal)
Size Range
- Simplex Compact S
- Simplex Compact M
- Simplex Compact L
- Simplex Compact XL
Drive Type
Passive
Construction
Multi-lip rubber seal, chrome liner, spring-loaded
Common Failures & Inspection Points
- Lip seal wear from shaft liner scoring
- Chrome liner pitting from seawater corrosion
- Seal housing bolt corrosion/seizure
- Oil loss from worn aft seal
Service: Same as Wärtsilä seals. Drain inspection daily. Seal replacement at drydock. Chrome liner reconditioning or replacement if scored. Oil analysis every 3 months.
Spare Parts: SKF Marine (Gothenburg, Sweden). Simplex seal kits: 3-6 weeks. Chrome liners: 6-10 weeks.
Strengths
- Compact design fits restricted stern tube spaces (S, M, L, XL sizes).
- Passive drive eliminates external actuation mechanisms, reducing complexity and maintenance.
- Proven reliability since the 1950s with extensive field service history.
- Standardised dimensions allow easy replacement on most medium‑power vessels.
- Oil retention capability simplifies daily drain inspection routines.
Weaknesses
- Rubber lip material limits maximum operating temperature and power compared with active seals.
- Chrome liner can suffer pitting if seawater ingress is not tightly controlled.
- Seal housing bolts are prone to corrosion in aggressive marine environments, requiring periodic inspection.
- Replacement typically requires dry‑dock access; not a quick‑change solution.
Typical Vessels:
Bulk carrierProduct tankerContainer shipOffshore supply vesselRo‑Ro ferry
Certifications:
DNV GL approvalABS classification approvalLR (Lloyd's Register) approval
Decision Guide: Choose if: you need a compact, low‑maintenance seal for medium‑power shaft lines where space is limited and passive operation is preferred. Avoid if: the propulsion system exceeds high power/temperature limits (>10 MW) or requires an actively driven seal for extreme service conditions.
Use Cases: The Simplex Compact Seal is commonly installed on new builds and retrofits of merchant vessels with conventional shaft lines, providing reliable oil containment in routine operations and during dry‑dock overhauls. It is especially favored where daily oil drain checks are part of the maintenance regime.
Thordon Bearings (Canada)
1
SXL / COMPAC Series
Shaft diameter 100-1,000 mm
· Seawater lubricated
· Water-lubricated stern tube bearing
Type
Water-Lubricated Stern Tube Bearing (Polymer)
Size Range
- SXL 150
- SXL 300
- SXL 500
- SXL 700
- COMPAC 150
- COMPAC 500
Drive Type
Passive (seawater lubricated)
Construction
Elastomeric polymer staves in bronze/steel housing
Common Failures & Inspection Points
- Bearing wear from sand/silt ingestion in shallow/coastal waters
- Uneven wear from shaft misalignment
- Stave debonding from housing in extreme conditions
- Noise/vibration from stick-slip at low speeds
Service: Bearing clearance measurement at drydock (poker gauge). Wear rate monitoring — typical life 15-25 years on deep-sea vessels, shorter on coastal. Shaft alignment check at each drydock. No oil pollution risk — environmentally compliant (VGP/EPA).
Spare Parts: Thordon Bearings (Burlington, Ontario, Canada). Replacement staves: 4-8 weeks. Emergency service: Thordon has 24/7 global support. Keep onboard: wear measurement tools.
Strengths
- Eliminates oil contamination risk – fully seawater lubricated and VGP/EPA compliant.
- Proven long service life (15–25 years) on deep‑sea vessels when operated in clean water conditions.
- Wide size range (SXL 150‑700, COMPAC 150‑500) covering most commercial propulsion shafts.
- Simple inspection method – clearance measured with a poker gauge at drydock.
- Robust elastomeric staves give good damping of vibration and noise under normal operation.
Weaknesses
- Highly sensitive to sand/silt ingestion; accelerated wear in shallow or coastal waters.
- Requires precise shaft alignment; misalignment leads to uneven wear and premature failure.
- Stave‑to‑housing debonding can occur under extreme temperature or pressure cycles.
- Stick‑slip phenomenon may cause noise/vibration at low ship speeds.
- Not suited for very high‑power shafts beyond the size limits of the series.
Typical Vessels:
Bulk CarrierOil TankerContainer ShipOffshore Supply VesselCruise Ship
Decision Guide: Choose if the vessel operates primarily in open‑ocean or deep‑water routes with low sediment load, needs an oil‑free bearing solution, and can schedule regular drydock alignment checks. Avoid if the ship frequently sails in shallow, sand‑laden coastal waters, performs extensive low‑speed manoeuvring, or cannot guarantee strict shaft alignment at each maintenance interval.
Use Cases: Thordon SXL/COMPAC bearings are commonly installed on deep‑sea cargo vessels and offshore support ships where long intervals between bearing overhauls are desired and environmental compliance is a priority. They are also fitted on cruise liners and large tankers that benefit from the reduced maintenance burden of passive seawater lubrication.
Vesconite (South Africa)
1
Vesconite Hilube Marine
Shaft diameter 25-500 mm
· Water lubricated / Dry running capable
· Self‑lubricating thermoplastic bearing
Type
Thermoplastic Polymer Bearing (Marine Grade)
Size Range
- Vesconite 25-100
- Vesconite 100-250
- Vesconite 250-500
Drive Type
Passive
Construction
Proprietary thermoplastic polymer, machinable, self-lubricating
Common Failures & Inspection Points
- Thermal expansion at high operating temperatures
- Surface scratching from debris ingestion
- Dimensional instability in fluctuating temperature environments
Service: Clearance check at drydock. Self-lubricating — minimal maintenance. Can run dry temporarily. Suitable for rudder, stern tube, and deck machinery bearings.
Spare Parts: Vesconite Bearings (Virginia, South Africa). Global distribution. Lead time: 1-3 weeks for standard sizes. Machinable from bar stock — emergency fabrication possible onboard.
Strengths
- Self‑lubricating – eliminates routine oil greasing and reduces maintenance intervals.
- Can tolerate short dry‑run periods without immediate damage.
- Corrosion‑resistant polymer material suitable for marine environments.
- Machinable to match existing housing dimensions, facilitating retrofit installations.
- Lower friction coefficient than traditional bronze or steel bearings, improving shaft efficiency.
Weaknesses
- Thermal expansion can become critical at high operating temperatures, requiring careful clearance checks.
- Dimensional instability when temperature fluctuates rapidly, potentially affecting bearing alignment.
- Surface scratching and premature wear if debris or foreign particles are ingested.
- Load‑capacity limits compared with metal bearings; not ideal for very high‑power shafts (>~500 kW).
- Limited long‑term field data in extreme Arctic or tropical temperature cycles.
Typical Vessels:
Bulk CarrierProduct TankerContainer ShipOffshore Supply VesselRo‑Ro Ferry
Decision Guide: Choose if you need a low‑maintenance, corrosion‑resistant bearing that can survive brief dry‑run events and you have good control of operating temperature and clearance. Avoid on high‑power shafts where metal bearings are required or in applications with severe temperature swings and high debris ingress risk.
Use Cases: Commonly installed as the stern tube bearing on medium‑size cargo vessels, as well as on rudder pivots and auxiliary deck machinery (e.g., winches, cranes) where a self‑lubricating polymer solution reduces oil handling and maintenance downtime.