Replacement of Marine Turbochargers.

Descriptions

On 18th Feb 2013, MAN Diesel & Turbo Issued a safety warning Alert Service Bulletin to customers who have type NR or NA turbocharges installed. The warning advised that that gray cast iron material of the turbocharger casing was safety critical and that the older the part, the higher the probability of failure.Having established that the issue affects vessels with type NA34/TM736 turbochargers, certain prohibition actions were implemented where crew were restricted ingress to the Machinery Rooms whilst engines were in operation. Following a risk assessment, the following initial technical solutions were proposed to the engine manufacturer:1. Agree a reduced or de rated power level for the engines below which the turbo chargers will be safe to operate due to reduced rpm and centrifugal forces.2. Design and manufacture a containment shield to fit around the gas casings.3. Change out the gas casing for a new safer type.4. Deliver, replace, test and commission turbo chargers complete with a new safe type (NA34/S)The first three proposals were rejected as unsafe by the engine and turbocharger manufacturer and CalMac Ferries Ltd (CFL) has no reason to doubt the validity of the conclusions reached/this has been independently verified, leaving direct replacement as the only safe option.