LOTE for Naval Vessels – Procedure and Experience

It is well known that navies today are facing increasing challenges to fulfil their more and more complex duties with aging fleets. This implies the need for system up-grades and for keeping the existing fleet longer in service than designed or planned for, especially considering very long lead times for newbuilding programs. In summary this puts additional pressure on limited budgets and resources and drive the demand for alternative solutions. To extend the original design lifetime of the existing vessels and investigate the potential to utilize their actual capabilities beyond the original design limitations is one of the most practical approaches to overcome this situation and fulfil the needs of future duties and commitments. For doing this in a safe and reliable way, DNV GL has developed a flexible, inclusive Life of Type Extension (LOTE) approach, as part of DNV GL’s Naval Technical Assurance Services. This is building on the in-service experience of platform systems from hundreds of naval vessels and support of new-build programs over a long period worldwide. Through a unique combination of numerical simulations and a tailored Navy CAP survey, the actual condition and the remaining service life can be determined. Furthermore, it is possible to investigate the effects of maintenance systems and modifications on the remaining life with respect to fatigue and corrosion as the focused degradation mechanisms. Due to the intensive involvement of DNV GL during the design phase of many combatants and the close cooperation between the building yards and DNV GL in this respect the application of the DNV GL LOTE approach for naval vessels is a perfect match. The consideration and consequent re-use of calculation models and calculation results from the design phase, whenever possible, offers both a consistent and seamless technical basis for the subsequent LOTE calculations and assessments as well as a most efficient approach from commercial point of view. Using the example and experience from a practical LOTE application for a typical surface combatant the thorough capabilities and benefits of the approach are shown. The general findings and results of this example are representative for a typical LOTE
application and confirmed by several different projects. Furthermore, the key learnings as well as areas potentially subjected to future development will be named.