STT 3
Schottel STT 3 — TransverseThruster - Medium transverse thrust.
Inspector Detail
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Common issues
- Shaft seal leakage into the thruster room bilge
- Bearing wear from prolonged low-speed, high-load maneuvering duty
- Hydraulic oil contamination in the pitch/thrust control system
- Blade or propeller tip erosion or cavitation damage
- Gearbox oil leaks at the input shaft seal
- Vibration from fouled or damaged blades
Inspection checklist
- Check tunnel/thruster room bilge for oil or water ingress
- Inspect shaft seal leakage rate against baseline
- Check gearbox and hydraulic oil level and condition (water/metal particle sampling)
- Inspect blades for cavitation erosion, cracks, fouling
- Check mounting bolts and flexible couplings for tightness and wear
- Verify control system response and emergency stop function
- Check tunnel grids/gratings for damage or blockage
Service intervals
| Gear oil sampling | every 6 months |
| Gear oil change | per Schottel's own interval, commonly annual or every 2,000-4,000 hours |
| Shaft seal inspection | annually or at each dry-docking |
| Hydraulic oil filter | per running hours or differential pressure indicator, whichever comes first |
Typical wear limits
| Shaft seal leakage rate | compare against the manufacturer's baseline drops-per-hour figure - a rising trend, not a single value, is the alarm signal |
| Gearbox bearing clearance | per Schottel's own service manual for this unit size, no generic figure applies |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Shaft seal kit
- Gearbox oil filter element
- Blade set (long lead item)
- Coupling/flexible element
- Hydraulic pump seal kit
Safety
- Stored hydraulic pressure in the pitch/thrust control system - isolate and de-pressurize before maintenance
- Rotating shaft and coupling - remove guards only with the drive isolated
- Confined thruster room access adjacent to voids/tanks - ventilate and gas-test before entry where applicable
Class survey
Note: the source record's typ field says 'Controllable-Pitch Propeller (CPP)' but the description identifies this as a transverse tunnel thruster - content above is written for a transverse thruster. Thrusters used for propulsion/DP notation fall under Continuous Survey Machinery or periodic thruster survey depending on class notation; class checks oil sampling records, seal condition, and function test including emergency stop and, where DP-classed, independent power/control redundancy.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Visual dive inspection or ultrasonic thickness measurement of blade leading edges for erosion, pitting, or cavitation damage indicative of operating outside design envelope
Dismantle controllable-pitch propeller hub, measure all bearing clearances and roughness, check for wear patterns; exchange all internal seals and gaskets
Visual inspection of sacrificial anodes and protective coatings; replace zinc anodes and check hull attachment for galvanic isolation
Verify shaftline re-certification, check flexible coupling bolts for looseness, measure runout and eccentricity of propeller hub to detect misalignment
Sample hydraulic oil for water content and particle count; inspect seal condition around hub oil passages for weeping or active leakage
Type-general inspection and maintenance points for this equipment category — not model-specific.
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