A valve failure on the CalMac ferry MV Glen Sannox last summer resulted in an uncontrolled escape of flammable gas, according to an investigation into the incident. The ferry was carrying 82 passengers at the time of the event, which occurred on a crossing from Arran.
The investigation identified that no fail-safe system, which would include valve position indicators and gas pressure sensors, had been installed to alert the crew to the failing valve. Wartsila, the engine supplier, had shipped the main engines to the shipyard in early 2017 without these monitoring systems. While Wartsila later began fitting them as standard on new engines and had installed them on the ship's smaller auxiliary engines, they were absent from the main engines on the Glen Sannox.
Standards body Lloyds Register may have approved the system based on the assumption that such safety features were present on all engines. These sensors have since been retrofitted to the Glen Sannox and will also be installed on its sister ship, MV Glen Rosa.
The specific valve that failed has been replaced with a new model. CalMac has also implemented additional training for its staff. Currently, the vessel is not operating on gas. In a statement, CalMac acknowledged lessons were learned following the June 2025 incident and that remedial actions have been taken.
"The vessel is absolutely safe to operate on LNG, and the decision not to re-gas her following annual overhaul at the beginning of the year was purely due to our desire to get her back in service as quickly as possible," CalMac stated. The Marine Accident Investigation Branch has reviewed CalMac's report and indicated its satisfaction with the firm's corrective measures.
When questioned about why fail-safe monitoring equipment was not initially fitted on the Glen Sannox, or who had access to its service notices, Wartsila cited client confidentiality as a reason for not answering specific questions. In a statement, the company affirmed its commitment to sustainability and maintaining high safety standards, quality, and reliability, adding that it works closely with customers throughout the lifecycle of its solutions, providing technical guidance and support.