The System Modeling Approach to Reliability and Safety

DR-FMEA is a system modeling tool that provides a structured method for examining each system component to verify that it is applied correctly and to determine the effect if the component fails. A basic requirement for any product is that no single component failure can have a catastrophic effect. If you find such a failure mode, you must find a way to mitigate the effect of failure. This is best done early in the Design Process.

DR-FMEA stands for “Design Review - Failure Mode and Effect Analysis”. The process begins by entering each component part used in the system. Next the user performs a rigorous Reliability Stress Analysis for each use use of the part  in the system. The user has the option of including humans as a system component. The results of the Reliability Stress Analysis are used as the basis for the FMEA.  DR-FMEA includes a Hazard Factor (H), for each Failure Mode so that Safety issues can be included in the basic FMEA. The H factor is the probability of Injury if the failure occurs. The possibility of Human Error is always present and DR-FMEA facilitates including Humans and Human Error as components and Failure Modes.

DR-FMEA was designed to be an easy way to verify that the design goals are met and all failure modes have been identified and mitigated early in the Design phase. The possible failure modes can be easily expanded to include Human Error, Instruction Sheets and Compliance with all applicable Codes. DR-FMEA is also an excellent documenter of the Design Review process.

DR-FMEA answers three basic questions:

  1. Does the design meet all of the contract requirements and comply with all of the applicable Codes & Standards?
  2. Is each component capable of reliably performing its function?
  3. What will happen when the component fails?

Creative Design is an iterative process so DR-FMEA was designed to follow the evolution of a design and keep track of the changes along the way. DR-FMEA can be used to analyze a single assembly or a complex system comprised of many assemblies, subassemblies and components. DR-FMEA is also an effective tool for managing the progress of a design and keeping everyone on the same page.

DR-FMEA uses a Part Number to define the characteristics of the part and a Parts List to define its function in the system. DR-FMEA defines the finished product as the Root-Assembly. Everything else is a component of the Root-Assembly, has a Part Number, and serves a specific purpose. Some components of the Root-Assembly may be assemblies of components, some of which may also be an assembly for many levels. To complicate things further, the same Part Number may be used many places for different purposes in a design. To get around this problem, DR-FMEA uses a hierarchical naming system to provide each component used anywhere in the system a unique name.

Anytime both humans and equipment are required to make the system work, both should be included as system components in the analysis. All systems are covered by one or more National Codes or Standards, which will be the standard that your company will be judged by if your product becomes involved in a lawsuit.

DR-FMEA allows the user to include humans, codes, manuals and any other items that that could affect the reliability or safety of a product. These non-traditional components are considered part of the product, given Part Numbers and treated like the hardware components. DR-FMEA also allows the user to expand the definition of a failure to include anything that can prevent a system from working.

DR-FMEA stores the information in a relational database where it can be retrieved, sorted and used in many different ways. It has reduced the information gathering process to four automated worksheets that makes extensive use of auto-complete fields, data lookup. DR-FMEA automatically generates related worksheet and transfers the relevant data. We have attempted to reduce the clerical burden while providing an efficient and easy way to use the tool. DR-FMEA also generates a meaningful status report, that lists both the resolved and yet to be resolved design issues.

The Part Number List is where each part number used in the system is listed along with its capabilities and limitations. For humans, the Part Number defines a skill-set. The Part Number is the Identifier used for codes and manuals.

The Parts List is where each component is entered into the system using its symbol from the drawings. The drawing or schematic is for a higher level Assembly. The Parts List relates the Symbol to a Part Number and describes its function in the system. When the Part Number is entered, the information from the Part Number List is automatically transferred to the Part List. For Humans the Symbol is the job title. For Codes, the Symbol is the Name of the Code. The Parts List is where the Reliability Analysis is performed.

A FMEA Worksheet is automatically generated each time a part is entered in the Part List. The basic information about the part and its application are automatically transferred to the form. The Failure Mode and Failure Effect are left blank. Having the basic information about the part on the form greatly simplifies the FMEA process. For humans, the failure mode is a human error.  For Codes, the failure mode is non-compliance with an article. Each Failure Mode is evaluated for Safety and is assigned a Hazard Factor (H). There is a button for additional failure modes.

Corrective Action Worksheet is derived from the FMEA Worksheet and is where a person is assigned responsibility for solving a problem and a date to get it done by.

DR-FMEA uses a Holistic Approach to Reliability and produces a result that is much greater than the sum of its parts.

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Bass Associates Inc.
13533 Larkin Drive, Minnetonka, MN 55305
Phone: 952/544-

Copyright 2009 John M. Bass P.E.     Last modified: June 25, 2015