ICDE project report: collection and analysis of common-cause failure of safety valves and relief valves

This report documents a study performed on the set of common cause failures (CCF) of safety and relief valves (SRV). The data studied here were derived from the International CCF Data Exchange (ICDE) database, to which several countries have submitted CCF event data. The purpose of the ICDE is to allow multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses that include CCF modeling. Because CCF events are typically rare events, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, yields sufficient data for more rigorous analyses. This report is the result of an in-depth review of the SRV events and presents several insights about them. The objective of this document is to look beyond the CCF parameter estimates that can be obtained from the CCF data, to gain further understanding of why CCF events occur and what measures may be taken to prevent, or at least mitigate the effect of, SRV CCF events. The report presents details of the ICDE project, a quantitative presentation of the SRV events, and a discussion of some engineering aspects of the events. This study examined 149 events in the ICDE database by tabulating the data and observing trends. Once trends were identified individual events were reviewed for insights. The database contains information developed during the original entry of the events that was used in this study. The data span a period from 1977 through 1999. The data is not necessarily complete for each country through this period. This information includes root cause, coupling factor, common cause component group (CCCG) size, and corrective action. As part of this study, these events were reviewed again and additional categorizations of the data were included. Those categories included the degree of failure, affected subsystem, and detection method. This study begins with an overview of the entire data set (Section Five). Charts and tables are provided exhibiting the event count for each of these event parameters. This section forms the baseline for the SRV component. Section Six contains charts that demonstrate the distribution of the same events further refined by failure mode (failure to open, failure to close and inadvertent opening) for each event parameter. Each of these charts is replicated with the further distinction that only those events classified as partial or complete are included. Distinctions are drawn as these parameters shift. Section Seven presents a qualitative assessment of the collected data, events are analysed with respect to failure symptoms and failure causes. Section Eight presents a summary and conclusions