Masada Mitsubishi deck crane hoisting gearbox replacement



Alatas Hong Kong received an urgent request to replace a damaged hoisting gearbox and conduct a load test promptly.


The client reported a malfunction in the hoisting function due to a damaged gearbox, necessitating replacement before the next discharging port.

Alatas Solution:

Alatas Service engineers successfully replaced the gearbox and conducted a load test within a tight timeframe of 15 hours per day.

Alatas Service Engineer Team Job Scope:

Upon arrival, the team discussed the job plan and requirements with the Chief Engineer for gearbox replacement. They then transferred all necessary tools and equipment from the launch boat to the vessel using crane no. 4.

  • Positioned the boom on a rest stand and lowered the hook weight completely onto the deck.
  • Positioned the hoisting winch drum to ensure the drain pipe was at the bottom.
  • Removed the luffing winch limit switch chain to slacken the wire rope, with assistance from the vessel crew.
  • Slacked the luffing and hoist wire ropes and secured them with a rope stopper and chain block.
  • Supported the hoisting winch with wood underneath it.
  • Secured the luffing winch drum with slings and wood underneath it.
  • Isolated the crane power supply and turned off the breakers.
  • Closed all respective stop valves and butterfly valves for the hydraulic system.
  • Drained gear oil from the hoisting winch gearbox and hydraulic oil from the tank.
  • Marked and disconnected all respective metal pipes and flexible hoses for the hoisting and luffing motors.
  • Disconnected metal pipes from both the motor and control blocks.
  • Removed the luffing motor, counterbalancing block, and hoisting motor.
  • To expedite the process, the team lifted and secured the luffing motor, counterbalancing block, and hoisting motor behind the operator cabin with a chain block, rather than removing them from the crane.
  • Removed cable connections that were hindering the main frame removal.
  • Removed the climbing ladder from the machinery house to access the gearbox removal area.
  • Dismounted the main support frame of the hoisting and luffing winches and opted to keep them inside the machinery room to save time on removal, rigging, and shifting of the main electric motor.
  • Applied heat to loosen large Allen screws on the hoisting motor mounting, successfully removing three (the remaining one was removed after rigging the gearbox down to a proper accessible area for work).
  • Used a puller frame to remove the hoisting gearbox from the winch drum.
  • Rigged and removed the old gearbox with the assistance of deck crane no. 2.
  • Cleaned the drum and worksite in preparation for fitting the new gearbox.
  • Rigged the new gearbox and shifted it inside the crane’s machinery housing with deck crane no. 2.
  • Positioned the new gearbox for proper drainage and fitted the drain pipe, utilizing wooden blocks for alignment.
  • After encountering initial difficulty, successfully fixed the gearbox inside the housing on the second attempt.
  • Faced challenges tightening the drain pipe due to slipping threads, but resolved the issue by tapping the gearbox drain hole and reattaching the pipe securely.
  • Torqued the gearbox mounting bolts and the winch mounting main frame bolts.
  • Applied flange sealant and thread lock to the contact surfaces and mounting bolts of the hoisting and luffing motors.
  • Reconnected all hydraulic hoses, metal pipes, and electrical cables previously removed by the vessel crew.
  • Cleaned the crane’s machinery housing and removed all tools and equipment.
  • Reattached the luffing winch limit switch chain with assistance from the vessel crew.
  • Filled both the hoisting and luffing winch gearboxes with oil and topped up the hydraulic oil.
  • Opened all closed hydraulic valves.
  • Released both hoisting and luffing ropes.
  • Bled air from hydraulic systems at bleeding points.
  • Conducted thorough checks on the crane, including idle operation, leak detection, and abnormal sound inspection.
  • Operated the crane without a load to ensure proper functioning.
  • Checked all crane functions and parameters, adjusting the boom-up limit as needed.
  • Conducted a load test with a 30-ton load, meeting the vessel crew’s requirements and completing it satisfactorily.


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