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Project

Thruster Overhaul Services for Kawasaki KT-55 B3 Thruster on AHTS Vessel in Nigeria

Table of Contents

Background

Industry
Marine
Solution
Major Overhaul of Bow and Stern Thrusters
Make & Model
Kawasaki KT-55 B3
Thruster
Asset
Anchor Handling Towing Supply Vessel (AHTS)

Summary About The Project

Neptunus carried out the major overhaul of two bow thrusters and one stern thruster equipped with Kawasaki KT-55 B3 Thruster units on an AHTS vessel in Nigeria. The work included dismantling and workshop shifting of the thruster assemblies, gear case inspection, input shaft and propeller shaft assembly overhaul, component measurements, Dye Penetrant testing and replacement of required OEM spare parts.

New bearings, seals, liners, O-rings, gaskets, shims, locking components and other related spares were installed as required. Axial displacement, gear backlash, pitch movement and other operational checks were carried out. Stern tube seals were inspected and renewed, while the stern thruster seal housing top plate was machined by a third party after damage during dismantling.

The thruster assemblies were reassembled and fitted back in position. Pitch zero and operational checks were carried out satisfactorily. A sea trial could not be conducted due to the unavailability of propeller shafting.

Planning

  • Team Composition: Neptunus Service Team of 5 with technical expertise led by a team leader.
  • Duration: 16 December 2024 to 8 January 2025
  • Work Scope:
    Major overhaul of two bow thrusters and one stern thruster, including dismantling, workshop shifting, gear case overhaul, input shaft and propeller shaft assembly inspection, component measurements, Dye Penetrant testing, replacement of required OEM spare parts, stern tube seal renewal, calibration, reassembly, installation and operational checks.

Procedure Carried Out

1. Thruster Dismantling and Workshop Shifting:
  • Oil was drained from the thruster assemblies.
  • Water and oil were found in the bow thruster and stern thruster units.
  • Eye pads were welded in both bow thruster and stern thruster tunnels.
  • Foundation bolts and blade bolts were loosened.
  • Both bow thrusters and the stern thruster assemblies were brought down and shifted safely to the workshop.
  • Thruster assemblies were mounted on stands for dismantling and reassembly.
  • Components were dismantled and thoroughly cleaned.
2. Gear Case Assembly Overhaul:
  • Required gear case components were subjected to Dye Penetrant testing.
  • DP test results were found satisfactory.
  • Component measurements were taken and recorded.
  • Thruster assemblies were overhauled with new spare parts as required according to OEM specifications.
  • Axial displacement was adjusted.
  • Gear backlash was adjusted.
  • Pitch movements on both sides were tested using air pressure.
  • Stern tube seals were inspected for oil leakage.
  • No oil leakage was observed from the stern tube seals.
  • Rope guards and wire lashings were carried out.
3. Input Shaft Assembly Overhaul:
  • Two bow thruster and one stern thruster input shaft assemblies were safely dismounted.
  • Bearings were removed from the assemblies.
  • Components were cleaned thoroughly.
  • Required components were subjected to Dye Penetrant testing and found satisfactory.
  • Measurements were taken and recorded.
  • Input shaft assemblies were inspected and reassembled with new bearings.
  • The assemblies were mounted back into the gear cases.
  • Axial displacement was adjusted.
4. Propeller Shaft and Hub Assembly Overhaul :
  • Two bow thruster and one stern thruster propeller shaft and hub assemblies were dismounted from the gear cases.
  • Bearings, gears, couplings, hubs and crossheads were removed.
  • Components were cleaned and inspected.
  • Required components were subjected to Dye Penetrant testing.
  • Measurements were taken and recorded.
  • Propeller shaft assemblies were reassembled with new bearings.
  • Existing gears, couplings, hubs and crossheads were reused and tightened according to OEM specifications.
  • Propeller shaft assemblies were mounted back into the gear cases.
  • Axial displacement was adjusted.
5. Dye Penetrant Testing and Component Inspection:
Dye Penetrant testing was carried out on the required components of both bow thrusters and the stern thruster, including hubs, gears, crank discs, crossheads, sliding shoes, vertical shafts, propeller shafts, propeller blades, propeller bolts and couplings. The tested components were found to be in good condition.
6. Stern Tube Seal Overhaul:
  • Stern tube seal housings were dismantled and cleaned.
  • Seal housings were reassembled with new seals, liners and gaskets.
  • The stern thruster seal housing top plate was damaged during dismantling.
  • The damaged top plate was machined by a third party.
  • New liners, seals and related components were installed as required.
7. Blade and Feedback System Work:
  • Propeller blades were removed and inspected.
  • Worn propeller blades were machined.
  • Blade carriers, crossheads and related components were cleaned.
  • New O-rings and required sealing components were installed.
  • Feedback system components were reassembled.
  • Pitch zero position was checked.
  • Pitch movement and operational checks were carried out satisfactorily.
8. Final Assembly and Fitment:
  • Final thruster assemblies were shifted from the workshop for installation.
  • Thrusters were mounted and tightened.
  • Required wire lashing was completed.
  • Propeller blades were fitted and tightened according to OEM specifications.
  • Feedback chains and covers were installed.
  • Motors were attached, fitted and tightened.
  • Final pitch zero and operational checks were carried out.

Recommendations

The hub should be machined during the next overhaul. Oil conditions should be tested and monitored every three months. Routine header tank oil level checks should be carried out. Any abnormal temperature or vibration should be monitored, and the service provider should be contacted if any abnormality is observed.

Pre-Commissioning and Load Trials

Pitch zero and operational checks were carried out satisfactorily after final assembly and fitment. A sea trial could not be conducted due to the unavailability of propeller shafting.

Scope for Improvement

Regular oil condition monitoring and header tank oil level checks can help identify possible contamination, leakage or lubrication-related issues at an early stage. Periodic inspection of the hub, propeller blades, shaft assemblies, seals and gear case components is recommended to support reliable thruster performance and reduce the risk of unexpected downtime.

Conclusion

The major overhaul of two bow thrusters and one stern thruster equipped with Kawasaki KT-55 B3 Thruster units was completed on an AHTS vessel in Nigeria. The work included mechanical inspection, component testing, shaft assembly overhaul, seal renewal, replacement of required OEM spare parts, calibration, reassembly and operational checks. The thrusters were restored and fitted back in position, with pitch zero and operational checks completed satisfactorily.

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