CALMAC has warned of making compensation claims as a new investigation is launched into why Scotland's biggest publicly-run ferry broke down causing disruption across the islands network for seven weeks.

State-run ferry operator CalMac say that the early indications are that the issues with the eight-year-old MV Loch Seaforth were because one of the 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.

CalMac says that these piston screws should have been replaced at a dry-docking schedule of the Loch Seaforth in 2019.

A full and independent report has now been commissioned from a leading global investigations company to investigate why this did not happen.

And CalMac has said that it will be subject to claims that may take some months to resolve. 

MV Loch Seaforth was taken off the Ullapool-Stornoway route by state ferry operator CalMac in mid-April to be taken into dry dock for "major" engine repairs.

It led to six delays in getting the vessel back in service as repairs continued before coming back into services at the end of May.

READ MORE: 'We again apologise': CalMac's biggest vessel finally returns after seven weeks of ferry chaos

The Herald revealed how the failure of Loch Seaforth resulted in cuts to other services across the ferry network as vessels relied on with other routes were shifted around to accommodate.

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Campaigners had described the situation as a "national scandal" and that those responsible should already have lost their jobs for the state of Scotland's ferries.

CalMac say that subsequent repairs to the engines should have seen the ferry return to service on May 17,  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 May 31 while further remedial work was performed.

CalMac says it has  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.”