Product introduction
The stern tube bearing carrier is the housing that locates the aft and forward stern tube bearings around the propeller shaft and transmits shaft loads into the stern frame or hull. It must hold the bearing bore concentric with the shaft axis while permanently immersed in seawater or oil. Casting integrates the bearing sleeve seat, the bolting flange, the lubrication grooves and the sealing arrangement into one rigid body, rather than a welded fabrication needing stress relieving and repeated inspection. CNC turning and line boring then bring the bearing bore, flange face and seal grooves to the concentricity and finish that determine bearing life and shaft alignment.
Specifications
| Parameter | Specification |
|---|---|
| Materials | Nickel-aluminium bronze C95800 / CuAl10Fe5Ni5; duplex stainless 2205 (UNS S32205); super-duplex 2507 (UNS S32750); CF8M / 316L; ductile iron QT450-10 for inland and short-sea service |
| Process | Investment casting or resin sand casting + CNC turning, line boring, milling, drilling and tapping |
| Dimensional tolerance | ISO 8062 CT6–CT8 (CT6 on bearing bore and seal fits, CT7–CT8 on flange and outline) |
| Machining allowance | 3–6 mm on bearing bore; 2–4 mm on flange faces and bolt seats |
| Surface finish | Ra 3.2 um as-cast / shot-blasted; Ra 1.6 um on flange faces and bolt seats; Ra 0.8 um on bearing bore and seal grooves |
| NDT | 100% ultrasonic testing of the bearing sleeve wall and flange-to-barrel junction; dye penetrant testing of all machined surfaces; radiographic testing of the flange-to-barrel transition and oil galleries where specified |
| Pressure testing | Hydrostatic test of the oil chamber at 1.5 x design pressure for oil-lubricated designs; air-under-water test or helium leak test of the sealing circuit on request |
| Heat treatment | Solution annealing for bronze and duplex grades; stress relieving after rough machining; hardness and grain-size verification |
| Alignment | Concentricity of bearing bore to flange pilot held within 0.05 mm TIR or per drawing |
| Size range | Bearing bore 120–900 mm; flange diameter up to 1,400 mm; up to 2,500 kg finished weight |
| Documentation | EN 10204 3.1 or 3.2, dimensional report with bore concentricity record, NDT report, hydrostatic test certificate |
Key features
- One-piece cast carrier with integral bearing sleeve, bolting flange and seal housing for maximum rigidity.
- Bearing bore line-bored after heat treatment to hold concentricity with the flange pilot within 0.05 mm TIR.
- Ni-Al-bronze C95800 gives proven seawater compatibility and galvanic compatibility with bronze propellers.
- Oil chambers hydrostatically tested at 1.5 x design pressure with a witnessed hold period and certificate.
- Water-lubrication grooves, oil galleries and sensor ports cast in and machined to the drawing.
- Compatible with white metal, composite and polymer bearing linings; we can supply the carrier bare or lined.
Applications
- Oil-lubricated stern tube aft and forward bearing carriers on merchant ships.
- Water-lubricated open stern tube bearing carriers for environmentally sensitive and freshwater trades.
- Podded and azimuthing thruster shaft bearing housings.
- Dredge pump and tunnel thruster shaft bearing carriers.
- Stern tube refurbishment and re-bearing projects during dry dock.
Quality and compliance
Ningbo Ruican manufactures stern tube bearing carriers under its IATF 16949 certified quality management system, with documented melt control, spectrographic verification and mechanical testing for every heat. Castings ship with EN 10204 3.1 certification as standard; EN 10204 3.2 certification is provided when your inspector or nominated class society surveyor countersigns the test results. Ultrasonic and dye penetrant examination of all critical sections, hydrostatic testing of oil chambers and a full dimensional report — including bore concentricity and seal groove geometry — are issued with every delivery, and witness testing by your nominated class society (LR, DNV, ABS, BV, CCS, NK or other) can be arranged on request. Ningbo Ruican supplies the machined casting and its documentation; class-society type approval of the complete shafting installation is obtained by the yard and equipment maker.
FAQs
Do you supply the carrier with the bearing lining installed?
We can. The carrier can be delivered fully machined and ready for your lining subcontractor, or delivered with white metal, composite or polymer lining fitted and final-bored by our approved partner, with the bond and dimensional check documented.
How do you keep the bearing bore concentric with the flange?
The carrier is rough-machined, stress relieved, then finish line-bored in a single set-up with the flange pilot and face, so all datums are generated from one clamping. Concentricity is recorded on the dimensional report.
What pressure test do you perform on oil-lubricated carriers?
Oil chambers are hydrostatically tested at 1.5 times design pressure with a witnessed hold period and a signed certificate. Where the drawing specifies, we also perform an air-under-water or helium leak test of the sealing circuit.
Which grade do you recommend for water-lubricated stern tubes?
Nickel-aluminium bronze C95800 / CuAl10Fe5Ni5 is the most widely used because it resists seawater corrosion and erosion and is galvanically compatible with bronze running gear. Duplex 2205 or super-duplex 2507 is chosen when higher strength or chloride resistance is needed.
Can you work from a sample part instead of a drawing?
Yes. We offer reverse engineering from a worn sample, including 3D scanning, material analysis and drafting of a manufacturing drawing for your approval before tooling is cut.
