Overview
QuantiServ recently completed a large-scale repair assignment on a passenger ferry. The ferry was built in the year 2000 and is equipped with four 12-cylinder, 46-bore main engines, with a nominal power output of 12.6 MW each.
In early 2024, two of these engines required extensive repairs, having each accumulated over 120,000 running hours and having suffered a recent failure.
QuantiServ was contracted to carry out the repair of both engines. As additional defects were found during the repair, the work turned into a sizeable project that took almost four months to complete.
Our in-situ machining specialists from Sweden carried out all work during the winter months of 2023/2024, while the vessel was out of operation during the low season.
Damage
The following damages were found. They were all addressed by our specialists during the repair.
Engine Number 1
- Crankpin bearing failure
- As a consequence: Multiple cracks, excessive surface hardness of 600 – 680 HB
Engine Number 2
- Failure of four crankpin bearings
- Crankshaft bent
- Failure of one adjacent main bearing
- A collapsed main bearing saddle, as a consequence of the heat generated
- Poor fitting of another bearing saddle
- Severe cam effect on all other crankpins
Detailed Work Performed
All repair works was done while the vessel was berthed during low season.
Engine Number 1
Crankshaft Repairs:
- Heat Treatment and Machining: One crankpin was machined to an undersize of -3.00 mm.
- Polishing: Two main bearings were polished to ensure smooth operation.
Engine Number 2
Due to damage found on the engine block, the crankshaft was removed so that line boring on the block could be carried out. Heat treatment and in-situ machining on the crankshaft was carried out on the vessel’s car deck.
Crankshaft Repairs:
- Heat Treatment: Four crankpins and one main journal underwent heat treatment.
- Machining: The treated components were machined to undersize diameters ranging from -2.00 to -5.00 mm, depending on their condition.
- Straightening: The crankshaft, found bent with a run-out of 1.50 mm, required peening (in-situ straightening).
- Polishing: All main journals and crankpins, exhibiting strong indications of the “cam effect,” were polished.
Engine Block Repairs:
- Bearing Saddle Realignment: The overheating of one main bearing caused misalignment, necessitating the replacement of the bearing cap and subsequent line boring.
- Bearing Cap Adjustment: Another main bearing cap showing a gap with the cylinder block was corrected.
Additional Improvements
In addition to the primary repair tasks, QuantiServ addressed machining work previously carried out by another company on some of the crankpins. The fillets were not nicely cut, and the radius around the oil hole needed improvement. Our specialists refined these areas, ensuring optimal performance and longevity of the crankshafts.
Summary Table of Work Done
| Engine | Work done |
| # 1 | Heat treatment and machining to -3.00 mm undersize of one crankpin |
| Polishing of two main bearings | |
| # 2 | Removal of the crankshaft for external heat treatment and in-situ machining |
| Machining to undersize diameters of -2.00 to -5.00 mm | |
| Peening (in-situ straighening) to correct a bent crankshaft with 1.50 mm run-out | |
| Polishing of all main journals and crankpins | |
| Replacement of a bearing cap and line boring due to misalignment | |
| Adjustment of a main bearing cap gap with the cylinder block |
Conclusion
This extensive in-situ repair project on a passenger ferry highlights QuantiServ’s expertise and ability to perform critical repairs without interrupting service.
The phenomena known as “cam effect” or “ridge wear” could be identified as reason for the bearing failures and the ensuing, rather extensive and therefore costly, repairs. It is therefore very important that ship owners and operators are sensitive to this issue and regularly check the condition of the crankpins once their engines have surpassed aproximately 60,000 running hours.
