Parts and Assembly Storage Life: How to Determine and Manage

In this presentation, Dr. Diganta Das will cover traditional standards and their limitations, methods of determining shelf lives through the use of critical failure mechanisms and elements of storage management that can extend storage life.

Many industries (such as aerospace, nuclear) own and operate high value products, which have to be manufactured or supported for long periods. Electronic part obsolescence caused by rapid changes and technological improvements are challenge for such industries. As a mitigation technique, lifetime buys and bridge buys are often conducted. Some industries (e.g., commercial aviation, power plants, semiconductor manufacturing) often enter into availability based contracts with their suppliers. The suppliers are often penalized for any downtime and hence it is necessary to be able to repair or swap out problem assemblies or parts to maintain contractually required uptime and hence need to keep spare parts and assemblies at their customer locations. In both of these cases, one needs to have confidence that the parts and assemblies stored will be operational when needed.

There is a clamor in the industry for having a shelf life estimates for part and assemblies but the available information is incomplete, confusing and often misinterpreted. There are inconsistencies in shelf life interpretations and inadequacies in recommended shelf life values invalidate the direct adoption of shelf life values from standards and manufacturers’ documents in most cases. Apart from storage environment and materials information of the unit being stored, shelf life also depends on, but not limited to the following factors. These factors determine the failure mechanisms active in the degradation of the items in storage.

• Quality of the unit being stored
• Life cycle stresses prior to storage
• Procedures or life cycle stresses after storage

In addition, in some cases, there are opportunities of additional storage management techniques based on physics of failure and health monitoring and management. In this presentation, Dr. Das will cover traditional standards and their limitations, methods of determining shelf lives through the use of critical failure mechanisms and elements of storage management that can extend storage life.