Inspection and repair of FLENDER 401-912-830-022-2

Scope of work:

We performed an inspection and repair on a gearbox FLENDER 401-912-830-022-2.

The conversion operations consists of:

• Disassembly of the gearbox
• Disassembling of the gearbox took 1 day without facing major issues.



• Transporting of parts to our workshop
• The pinion as well as the bull gear were transported to the workshop of the shipyard. Hoisting points needed to be welded on the ceiling of the pump motor room. The weight of the bull gear including the coupling is approximately 4 tons.



• Assembling in our workshop
• During assembly, all bearings and seals were renewed. End covers were machined to the required axial bearing play. Multiple parts were renewed: input shaft, pump gear, oil pump, astern shaft, clutch plates etc.



• Bearing replacement
• The coupling hubs were removed from the shafts with a high pressure oil injection system.
• Bearings were carefully removed with a heater/cutter torch.
• The seals installed were non-contacting and still in good condition. Spare seals were not available. It was decided to re-use the old seals.
• New bearings were heated up with an induction heater.
• Couplings were reinstalled with a 100 tons jack in combination with the oil injection system. The coupling of the pinion needed approximately 30 tons of pressure in combination with 1100 bar injection pressure.

  The coupling of the bull gear needed 80 tons of pressure in combination with 1500 bar injection pressure. It is important to have a M10 x 1 adapter available for the coupling hub on the pinion. Both cylindrical bearing of the pinion (input shaft) showed cracks on the inner race. The distance between the cracks was equal to the distance between the rolling elements. This suggest that the damage started when the gearbox was not running.




• Assembly of the gearbox
• Non hardening Hylomar (liquid gasket) was used between the split lines of gearbox and bearing covers. Split line bolts were fastened with a flogging spanner. Coupling bolts were tightened with a torque wrench according to the specified torque values. The oil of the gearbox was replaced. The gear coupling was filled with new oil. Gear clearance was checked and found acceptable.



• Testing
• The electrical oil pump was started. No leaks were observed. Testing of the gearbox itself was not possible. The coupling alignment was not checked. No indications were found that would suggest that the alignment was incorrect.