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Using failure modes and effects analysis in a reliability-centered maintenance program

11 steps can help prevent minor and major system failures in a metal fabricating facility

Nothing says “I screwed up!” like a line shutdown because your maintenance team neglected to replace a failing bearing. Nothing can be more embarrassing than spending days searching for the cause of dimpling in parts, only to find that the problem was paint chips falling onto the die. Some failures, like plant explosions or VOC emissions, have consequences such as investigations from the Occupational Safety and Health Administration, serious injuries, death, and long-term damage to your company's reputation.

Failure modes and effects analysis (FMEA) offers you the opportunity to manage your organization's collective experience and knowledge to prevent the pain and irritation of system failure.

The most important component in a successful reliability-centered maintenance(RCM) program is your ability to anticipate and prevent serious failure. FMEA is a proven and effective tool to help you identify potential failures. Understanding the consequences of failure should drive your maintenance planning. An effective and affordable maintenance plan focuses on preventing the critical and costly consequences of system failure on your plant floor.

FMEA is a framework to guide you in documenting your experience with and understanding of plant systems. FMEA guides you in identifying potential failures, the causes of failures, the consequences of system failures, and activities to prevent failures before they occur or remedy them after they happen.

The best way to introduce FMEA is to walk you through the process of defining failure modes and effects. The following is a list of the activities involved in conducting an FMEA. Understand that plants can be dynamic environments. As new equipment, processes, and systems are employed, the FMEA process should be revisited to incorporate the failure risks introduced into your plant.

The FMEA Process

FMEA is, quite simply, a thought-provoking activity. Too often we identify processes and methodologies with filling out the forms. This is a serious weakness in our definitions of methods. Employee experiences, knowledge, and insights are among the most valuable assets in any business activity. The forms are a vehicle to direct our thoughts and capture them when completed. With this in mind, we'll discuss the steps in completing a successful FMEA project.

  1. Identify the system or subsystem you are evaluating and its scope. What is it you are reviewing? Where does it begin? Where does it end?
  2. Identify the functions and specified operating parameters of the system you are reviewing. What does it do? What measurable parameters must the system meet? Examples include press tonnage, cycle times, robotic transfer speed, and furnace temperature tolerances.
  3. For each identified function, determine all the potential ways a failure can occur. These failure modes might include corrosion, hydraulic leaks, misaligned dies, and die wear.
  4. For each failure mode, anticipate the consequences of failure on the manufacturing system, related systems, and the mission of the entire system of interest. In the metal forming world, this might include wrinkling, excessive springback, poor part quality, or overcycling.
  5. Specify the severity of each failure mode, usually on a scale of 1 to 10. 1 = somewhat trivial; 10 = catastrophic.
  6. Define the potential root causes of each failure mode.
  7. For each cause, define the expected frequency of the event occurring on a scale of 1 to 10. 1 = infrequent; 10 = often.
  8. Define the available process controls for each root cause. Of course you check your tonnage monitors and record their values, don't you?
  9. Rate the ease of detecting each cause on a scale of 1 to 10. 1 = easily detected; 10 = hidden failure. Looking at a tonnage monitor isn't all that hard, is it?
  10. Calculate each subsystem’s risk priority number. This is Criticality x Frequency x Detection rating.
  11. Calculate the criticality of anticipated failures on your subsystem. This is Criticality x Frequency.

Once completed, your FMEA provides a solid foundation for predictive maintenance planning. When approached as a continuous process improvement program, RCM and FMEA can improve both production and design effectiveness. They also can improve equipment performance over its life cycle and support the development of cost-effective maintenance strategies.

About the Author
4M Partners LLC

Bill Frahm

President

P.O. Box 71191

Rochester Hills, MI 48307

248-506-5873