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MV Loch Seaforth - investigation into breakdown

Investigations into the breakdown of the Loch Seaforth that led to disruption across the CalMac network are nearing completion.

Early indications are that piston screws may have failed causing a breakdown of the port engine. One of the piston crowns separated from the body of the piston and damaged the cylinder head and liner. This damage then caused debris to enter the oil system. These piston screws should have been replaced at a dry-docking schedule of the Loch Seaforth in 2019. A full and independent report has been commissioned from a leading global investigations company to investigate why this did not happen.

Subsequent repairs to the engines should have seen the ferry return to service on 17 May but further and separate damage was caused by the presence of debris in the system when the engines were started up. This delayed the return to service until 31 May while further remedial work was performed. We have worked closely with the engine manufacturer who were commissioned to perform the repair to establish the cause of the start-up failure and they have acknowledged responsibility for failure to thoroughly clear the engine of debris.

CalMac Managing Director Robbie Drummond said: "Up until now our entire focus as a company has been on returning the Loch Seaforth to service so that we could address the impact her loss was having to our customers. That has now been achieved successfully and I would like to reiterate my sincere and heartfelt apology for the disruption this incident and the knock-on effects it caused.

"We are taking full accountability for the incident and are already investigating exactly what happened. We have selected a global incident investigation company who lead and facilitate major investigations worldwide to prepare an independent report on the process. Technical investigations by the engine manufacturer are ongoing, including metallurgical analysis on the screws to determine the root cause of the failure. Results will take up to eight weeks and may not be conclusive. We will implement all recommendations in full made by the independent investigation company to mitigate against situations like this happening in future.

"It is important to state that the matter is sensitive as it will be subject to insurance and potential warranty claims which will take some months to resolve. Claims will be subject to commercial confidentiality, so we are restricted in saying anything further at the moment. However, I want to reassure our customers and our stakeholders that we are in the process of checking all other technical bulletins and are putting processes in place to mitigate against this kind of incident happening again."


There were two separate incidents that led to the Loch Seaforth being out of service for a period of time.

The original incident was caused by a piston crown separating during operation. Whilst repairing the Port Engine, the manufacturer Wartsila and CalMac engineers conducted intrusive inspections and checks to attempt to determine the root cause of the failure and Wartsila (OEM - Original Engine Manufacturer) subsequently provided a technical report. It has not been possible to definitively identify exactly what component failed leading to the damage, but it can be stated that one of the piston crowns separated from the body of the piston and damaged the cylinder head and liner. This damage then caused debris to enter the oil system. There is an ongoing metallurgical investigation to determine if the piston screws failed in operation and this will take around eight weeks to complete.

The crew reaction was extremely quick to the developing incident. The engine was shut down quickly by the vessel crew in accordance with all the protocols and procedures and their quick actions undoubtedly restricted the damage. Running the engine much longer could have resulted in further damage and longer time off service for repairs.

During the inspections it came to light that the piston screws, which connect the body of the piston and the crown, were an old type that should have been replaced. There is an Original Equipment Manufacturer (OEM) bulletin that had been released from Wartsila detailing a requirement to replace the piston screws. The Port Engine was overhauled in 2019 and the piston screws should have been changed at this point, but it was evident that this had not been done as the old screws were still fitted. On inspection it was also found that the incorrect screws were fitted to the Starboard Main Engine, these were changed out during the repairs to the Port Main Engine.

A global incident investigation company who lead and facilitate major investigations worldwide  were contracted to investigate why the piston screws were not changed. New screws had been ordered for the 2019 overhaul and the intent was to complete the work. This work was conducted by the yards, subcontractors and supervised by the engine manufacturer. Opportunities to catch the failure by all parties were missed.

The initial repair required the engine to be stripped down to conduct detailed intrusive inspections. This included replacing the damaged piston and cylinder body and associated parts and inspecting and measuring components to ensure the extent of the damage was understood. All the piston screws were also changed which required all the pistons to be removed and overhauled. In addition, the whole engine required cleaning and the oil system flushed to clear out the debris from the engine. This process took four weeks, and the engine was ready for running on the 12 May.

This was when the second incident took place. At this point the engine test was initiated with agreement of all parties, including the OEM which was responsible for the repair. During the test there was a high bearing temperature, and the engine was shut down and inspected. Unfortunately, bearing damage was found to the assembly along with scoring of the crankshaft which was not there prior to the test. A separate technical investigation into this damage by the OEM found that an isolated piece of debris, that had not been flushed out, was drawn into a main bearing, and damaged it. As a result of this there needed to be a repair undertaken of the crankshaft, further strip, and inspections to ensure no further damage had occurred and a further system flush. This activity took a further two and a half weeks to accomplish. We have worked closely with the OEM to establish the cause of the start-up failure and they have acknowledged responsibility for failure to thoroughly clear the engine of debris.

There are ongoing warranty and insurance claims in progress as a result of the original incident and second repair which will likely take a number of months to fully resolve and we are unable to comment further on these at this time.

We fully support the recommendations from the independent investigation which we commissioned and will ensure that all lessons identified from this incident are being actioned. We will update our processes and procedures to ensure that we minimise the risk of a similar incident reoccurring by reviewing and updating our formal work control and management systems.

In particular, we are looking at how work is instructed to our subcontractors, overseen, and checked, to ensure they, and we, have a detailed understanding of what work they are expected to be doing when engaged to conduct work on our behalf.

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