Original Date: 01/23/1995
Revision Date: 01/18/2007
Best Practice : Pentagon-S: Safety Critical Piece Part and Defect Control
Sandia's High Consequence Surety Engineering Department introduced a new centralized Pentagon-S process to identify safety critical design features and their manufacturing controls for high-risk, high-consequence products and processes. Traditionally, a Pentagon-D or Pentagon-M notation on a design print was annotated by design and manufacturing engineers for quality control, indicating to manufacturers the degrees of freedom to deviate from specified tolerances, materials, or processes. The annotation also outlined required pedigree quality control procedures to capture this information during the production process. This process did not consider how and why safety control features were developed, what engineering safety analysis was performed, and the history of these features in production.
The new process is a multi-organizational team approach that works to define at a systems level review what features, processes, assemblies, inspections, tests, specifications, or materials are determined to be safety-critical features. System analysis tools are used (e.g., possibilistic, probabilistic and fault tree analysis) to determine what anomalies would potentially cause catastrophic events. The process helps the customer weigh safety requirements against other system requirements and understand the consequences of not implementing certain Pentagon-S controls.
With the Pentagon-S convention implemented, Sandia has demonstrated that safety is not just a concept, it is an attempt to control the effects of manufacturing on safety-critical features. In production program, Sandia successfully demonstrated an increase in production yield from 91% to 99% in the design for an Lightning Arrestor Connector component, a critical safety device for one of Sandia's weapon systems.
Designers, manufacturers, and vendors now understand their contributions to and responsibilities for safety, and it has created an auditable, pedigree trail to review all agreed-upon requirements. Additionally, as trade-offs are negotiated internally and lessons learned are captured, this data is archived and electronically accessible for future reference.
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