Modified Potential Failure Modes and Effects Analysis (FMEA) - A Description of A Modified FMEA and How It Helped Develop Dam Penetration Guidelines

摘要

The Flood Control District of Maricopa County (District) operates and maintains 22 flood control dams in Maricopa County, Arizona. Due to urbanization, requests to install buried utilities through District dams have increased significantly. As a result, the District and their consultants (the team), developed a Guideline to help applicants meet minimum design requirements for a utility penetration through a dam. The team recognized that risk assessment methods could greatly help to develop the Guideline by identifying the potential failure modes and consequences associated with various utility penetrations. However because any one of the District’s 22 dams could have a utility penetration, the team also recognized that the traditional Failure Modes and Effects Analysis (FMEA) procedures would not achieve the desired objective. Whereas the traditional method evaluates "knowns" about an existing dam, the project required evaluation of hypothetical "scenarios". The scenarios consisted of combinations of variables such as: the penetration location within a dam (freeboard, foundation, etc.), utility type (dry, pressurized liquid, etc.), conduit material type (steel, PVC, etc.), and construction technique (cut and cover, directional drill, etc.). Given the numerous potential combinations and the hypothetical nature of the scenarios, analysis using the traditional FMEA methods would be impractical. Hence, the process was modified to better serve the needs of the project. Several modifications were made to the FMEA. The modifications included developing a list of potential variables, grouping the variables, ranking the variables according to qualitative risk, and combining variables to create scenarios. Only the scenarios that were considered realistic would be further analyzed. Other modifications included using a step-wise process of analysis from low to high risk, re-defining the traditional failure mode categories, and including mitigation recommendations. By utilizing a modified FMEA, the team successfully identified potential failure modes and related mitigation technologies, both of which served as the basis of the utility penetration Guideline.