Case Study: Overhaul of Trønderbas Marine Gearbox


David Brown Santasalo (DBS) deliver bespoke gearboxes designed to meet our customers exact requirements. We have a strong reputation in the quality and efficiency of our mechanical power transmission systems, that are built to last.

Our customer, a family shipping company in the Marine and Ports industry has benefitted from a David Brown Santasalo purpose-built gearbox, which has been installed in their Trønderbas fishing vessel for the past 20 years. Since its installation in early 2000 the customer has experienced uninterrupted running of the gearbox.

In 2017, our team at DBS Sweden began regular endoscope inspections of the gearbox whilst in situ on the vessel. Our team of experts have a wide range of specialist equipment which enables us to be with our customers in the field, where and when they need us. Following the most recent endoscope inspection, we identified that the gearbox required an overhaul.

The team immediately ordered the necessary spare parts and the overhaul work was carried out in the dock at Rubbestadsneset, Norway. The scope of the work included disassembly of the marine gear and replacement of parts including wet disc clutches and high and low speed shafts. The team also changed the two-stage gear to a Power Take Off (PTO) Shaft to maintain 1200rpm on the shaft generator, to accommodate for the engine speed which is varied for different types of fishing.

Whilst the DBS team were in the process of replacing the bearings and slats, the customer had also decided to use the opportunity to make some changes to the gearing to increase the speed of the engine. To achieve this, we replaced all the gear wheels and the entire output shaft weighing eight tons. The overhauled gearbox can now achieve a new speed capability of 650 / 720rpm with 1200rpm out on the PTO shaft.

Following completion of the gearbox re-build, it was installed back into the vessel and a successful sea trial was carried out. The customer was extremely happy with the turnaround of this overhaul service and the flexibility they had to upgrade the gearing at the same time.

Chief/Technical Manager of the family shipping company said, “David Brown Santasalo recently carried out a total overhaul of the main gear on board the M/S Trønderbas. During an annual inspection of the gear unit carried out by personnel from DBS, indications of wear on the gear unit were discovered. We received a recommendation from DBS that it was time for an overhaul. Their basis for this was a careful review of the inspection report which was carried out when checking the gear. Our coordinator at DBS, Sales Engineer Peter Johanson, gave us a recommended overhaul plan and parts were ordered. We had regular contact with Peter to plan this work, who ensured we knew the timings for when the new parts would be delivered. DBS showed flexibility in when we could get this work done, since we as a fishing vessel have a busy operating schedule.”

“Marine Technicians Per Hedberg and Markuu Huusko from David Brown Santasalo were sent to Norway to supervise the overhaul. They received assistance from personnel from LOS Marine AS and Westcon Olvondo, and this worked optimally to get this job done. The team worked both efficiently and professionally, which in turn resulted in us not losing important fishing time for our shipping company,” he concluded.

To find out more about how David Brown Santasalo can overhaul your range of gearboxes, contact the team at

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