Overhaul of Kumera Gearbox for a Dredger Vessel in Drydock

Type of Project: Marine Gearbox Overhaul

Customer name: UK ferry operator 

Location: UK Docks Marine Services, Middlesborough

Summary

• Conducted a comprehensive inspection and overhaul of the Kumera gearbox.
• Replaced aged and worn components to ensure longevity.
• Successfully reassembled and tested the gearbox with a backlash measurement of 0.5mm.
• Achieved client satisfaction with the work carried out.
• Prepared the vessel for sea trials to ensure optimal performance.
• Demonstrated our expertise and professionalism in handling complex gearbox overhauls in challenging conditions.

Initial Enquiry

The client approached us with a requirement to overhaul a Kumera gearbox on their dredger vessel. The project involved dismantling the unit onboard, transporting it to our Hensall workshop for inspection and overhaul, and then returning it to the vessel for reassembly, testing, and sea trials.

Project Description

Upon arrival at the site, we immediately proceeded to the engine room to survey the job. The area around the transmission had been cleared for access, and the output coupling had been disconnected and removed due to the dredge pump being removed prior to our arrival. We drained the transmission of oil and found it to be in good condition. We were informed that lifting equipment had been ordered and was expected to arrive the following day.

We began by disconnecting the input coupling and removing it from the transmission flange. We inspected the input coupling and found it to be in generally good condition but decided to replace it due to its age and time in service. We removed all external parts, including pipework, the oil pump, and the oil cooler. We then removed the housing bolts in preparation for lifting off the top housing half.

Due to delays in obtaining the lifting equipment, we continued using alternative lifting methods. We removed the top cover, followed by the input shafts. Our initial inspections found no concerns. We then removed the middle housing and output shaft, and no issues were detected. We left the bottom half of the housing in place to aid alignment during reassembly.

We craned off all necessary parts from the vessel and transported them to our workshop. We cleaned the housings and tidied the work area before heading to the workshop to unload the items.

We stripped down and thoroughly inspected both shafts. We found the input shaft, gear, and flange to be in good condition, with only running markings present. We inspected the input flange and found it to be in good condition, but the shaft sealing diameter required machining. We also found the output shaft and gear to be in good condition, with the oil seal sleeve needing replacement. We inspected and replaced bearings as necessary. We tested and found ancillary items, including the oil cooler, oil pump, pressure switch, and temperature switch, to be in working order.

We returned all parts to the vessel. We cleaned the housing sections, paying particular attention to the sealing faces. We craned the output shaft onto the vessel and positioned it in the bottom half of the housing. We then sealed and bolted down the middle housing half, followed by the end covers. We hoisted the input shaft into position and temporarily bolted the end caps to locate the shaft. We took a backlash measurement, which was 0.5mm.

We hoisted the top cover into position, sealed, and bolted it into place. We removed, sealed, and refitted the end caps. We reinstalled all external parts, including the new oil cooler, oil pump, pipework, and oil monitoring panel. We assembled the input coupling but left both input and output couplings disconnected to allow for alignment once the pump cartridge was back in place and the vessel was floating.

Conclusion

We successfully completed the overhaul of the Kumera gearbox, inspecting, repairing, or replacing all necessary components. We reassembled and tested the gearbox, achieving a backlash measurement of 0.5mm. The client was highly satisfied with our work, and the vessel was ready for sea trials to ensure optimal performance. This project highlighted our expertise and professionalism in handling complex gearbox overhauls, even in challenging conditions, ensuring the longevity and reliability of marine transmissions.