This Safety Guide provides recommendations on a structured approach to the establishment and preservation of equipment qualification in nuclear installations, to confirm reliable performance of safety functions by such equipment during operational states and accident conditions, to avoid vulnerability due to common cause failure of the equipment. It applies primarily to equipment that performs one or more safety functions, but it may also be applied to items not important to safety, in accordance with national requirements. The qualification process covers electrical, instrumentation and control, and active mechanical equipment, and components associated with it, for example, seals, gaskets, lubricants, cables, connections, and mounting/anchoring structures. The qualification process for passive mechanical components for which the safety performance is assured by design in accordance with applicable codes, is outside the scope of this publication. The recommendations in this Safety Guide apply to new nuclear installations, and as far as is reasonably practicable to existing nuclear installations.