Safety Critical Items in naval systems
; and , 17th International Naval Engineering Conference & Exhibition, Liverpool, UK. IMarEST. doi:10.24868/11194
Abstract
What components make a ship safe to operate? Many; but not all are of equal importance. Applying a proportionate level of scrutiny and analysis to components and systems during design and safety case development, and then through life is key to the efficient management of the “safe to operate” argument. Applying true proportionality would be individual to every component and system– this would be cumbersome. Categorising safety related items to delineate between those that are essential to the platform safe to operate argument from those that provide a safety function that whilst important is not essential, allows appropriate focus to be placed on those essential items. Many would contend that this rationale has already been incorporated into existing design codes with terms in use such as Safety Critical Functions, Mobility or Ship Systems, Essential Services, Vital Services, Essential Safety Functions. However, these are generally loosely and subjectively defined and so open to interpretation. Furthermore, existing design codes tend to prescribe design outcomes. This leads to safety cases placing considerable emphasis and reliance on code compliance and certification rather than arguments focused on robust control and mitigation of hazards. Taking the lessons from offshore oil & gas, and other regulatory regimes and practices Defence Standard (Def Stan) 02-904, Surface Ship Safety Critical Items, was drafted to provide a consistent definition of Safety Critical Items and how they should be treated. The intent behind this standard is to generate a more risk focused approach to the management of component and system integrity through a platform life cycle and a leaner and more focused set of safety arguments. This paper examines the rationale behind Def Stan 02-904 and the work underway to implement its requirements.