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Project

Major Overhaul (MOH) of Niigata ZP-51 on Offshore Supply Vessel

Table of Contents

Background

Industry
Marine
Solution
Major Overhaul (MOH) of Propulsion System
Make & Model
Niigata ZP-51 CP
(Port & Starboard Units)
Asset
Offshore Support
Vessel (OSV)

Summary About The Project

The Offshore Supply Vessel was due for a complete overhaul of its Niigata ZP-51 CP azimuth propulsion systems. Neptunus was contracted to carry out a detailed inspection, service, and renewal of key steering and propulsion seal components to restore the vessel’s thrust reliability and steerage accuracy.

The overhaul was completed within 37 days and restored the propulsion and pitch control systems to full operational standards, verified through successful trials.

Planning

The vessel was due for a complete overhaul of its Niigata ZP-51 CP azimuth propulsion systems. Neptunus was contracted to carry out a detailed inspection, service, and renewal of key steering and propulsion seal components to restore the vessel’s thrust reliability and steerage accuracy.

Planned Activities

  • Disassembly of Port & Stbd ZP units
  • Seal and liner inspections
  • Seal housing renewals
  • Pitch control system overhauls
  • Hydraulic reassembly and torqueing
  • Non-destructive testing
  • Trials for steering and pitch control

Procedure Carried Out

STBD ZP Unit

  • Drained oil and disconnected feedback chain
  • Lowered and dismantled unit components (back cover, oil ring, hub, propeller blade)
  • Removed and cleaned seal housings and liners
  • Installed new seals, O-rings, and added 4mm spacer to adjust liner contact
  • Addressed liner line wear with 0.2mm material removal
  • Dismantled and rebuilt hub with new Belleville bolts
  • Performed hydraulic tightening and reassembly of hub and blades
  • Addressed liner line wear with 0.2mm material removal
  • Dismantled and rebuilt hub with new Belleville bolts
  • Conducted MPT and dye penetrant testing on propeller shaft, blades, crank pin, crosshead, and piston – no cracks found
  • Carried out pressure testing and filled oil – no leakages
  • Performed steering and pitch operation trial – satisfactory
  • Final steps: reinstallation of feedback chain, back cover, eye pads, bolts lashing, cementing, and rope guard fitting

STBD ZP Unit

  • Identical scope as STBD unit, including full seal renewal and pitch control assembly overhaul
  • Similar dismantling, cleaning, reassembly, and trial procedures executed

Gallery

BEFORE-ZP51-CP BOTH-SIDE-SEAL-REPLACEMENT
REMOVING-OF-HUB
HUB-DISMANTLING
HUB-ASSEMBLY-MOUNTING-ON KORT-NOZZLE
MOUNTING-OF-BED-STEERING-SEAL-HOUSING
LOWERING-KORT-NOZZLE-BY-CHAIN-BLOCKS
MOUNTING-OF-PROPELLER-BLADES-ON-HUB-UNIT
AFTER-ZP51-CP BOTH-SIDE-SEAL-REPLACEMENT

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