Understanding FMEA Compensating Provisions

Risk is a function of how poorly a strategy will perform if the “wrong” scenario occurs. Michael Porter

The use of Compensating Provisions in FMEA is a key part of many FMEA standards. Regardless of what FMEA standard you are using, everyone who aspires to doing FMEAs properly should understand the role of mitigating the risk of very high severity.

What are Compensating Provisions?

Let’s begin with definitions.

The definition of “compensate” is to “act so as to neutralize or correct (a deficiency or abnormality in a physical property or effect).”

The definition of “mitigate is “to make (something bad) less severe, serious or painful.”

According to MIL-STD 1629A, “Compensating Provisions are either design provisions and/or operator actions, which circumvent or mitigate the effect of the failure.” They are in essence a severity mitigation strategy.

What does it mean to mitigate the effect of failure?

To illustrate this concept, I’ll begin with an example relating to a power steering pump.

This is an excerpt from my article “Understanding FMEA Severity Risk – Part 1,”

Item: Power steering pump

Function: Delivers hydraulic power for steering by transforming oil pressure at inlet (xx psi) into higher oil pressure at outlet [yy psi] during engine idle speed

Failure Mode: Inadequate outlet pressure [less than yy psi]

Effect (Local: Pump): Low-pressure fluid goes to steering gear

Effect (Next level: Steering Subsystem): Increased friction at steering gear

Effect (End user): Increased steering effort with potential accident during steering maneuvers

In this example, the severity of the End Effect is safety related. The design team may or may not have provisions in the design to mitigate the seriousness of this consequence. Mitigating the effect of failure means to introduce design provisions and/or operator actions, which circumvent or make less severe the effect of the failure. For a very high severity rating, this means if failure occurs, the item fails in a safe manner.

What should the FMEA team enter in the Compensating Provisions column?

The FMEA team enters the Compensating Provisions that are currently planned or in place (if any). These are the design provisions and/or operator actions, which circumvent or make less severe the effect of the failure. At this point in the FMEA, the Compensating Provisions are not yet evaluated for how good they are.

What is an example of Compensating Provisions?

If the design of the power steering system includes a strategy to mitigate the effect of pump failure to a safe level, that would be a severity mitigation strategy. In our hypothetical example, the design of a power steering system includes a monitoring device for the power steering oil pressure, and an automatic system response when pressure goes below the safe level. The hypothetical system response would alert the driver to immediately address low oil pressure, before the steering reaches an unsafe level.

Evaluate Compensating Provisions

Once the Compensating Provisions are entered into the FMEA, the FMEA team should ask the question: are the Compensating Provisions good enough to take credit for reduction in severity rating? How do you know if Compensating Provisions are good enough to reduce severity? The question becomes whether the current mitigation strategy is sufficiently robust to change the end effect to a level that is safe. To answer this question, I’ll pose three conditional statements.

Conditional statement 1:

If the FMEA team believes the current mitigation strategy is sufficiently effective in mitigating the effect of failure, they can revise the End Effects description and initial severity rating accordingly. This means the FMEA team believes the mitigation strategy will result in a safe condition. This means they believe the monitoring system will detect the impending problem, and the response system will result in a safe condition. Based on this analysis, the FMEA team can reduce the severity rating accordingly.

Conditional statement 2:

If the FMEA team believes the Compensating Provisions are not sufficiently effective, the severity remains high, and the FMEA team should identify actions to improve the mitigation strategy. They enter these actions in the Recommended Actions column.

The FMEA team can consider a number of strategies to improve the effectiveness of Compensating Provisions and thereby reduce severity. In chapter 7 of my book Effective FMEAs, I discuss four strategies to reduce severity risk: design for fail-safe, design for fault-tolerance, design for redundancy, and provide early warning. Other strategies are possible. I write about these strategies in my article “Action Strategies to Reduce Severity Risk.”

Conditional statement 3:

If the FMEA team wants to use a more rigorous procedure to determine if the current Compensating Provisions are good enough to take credit for a reduction in severity, an optional technique is described in SAE J1739:2021 section on Supplemental FMEA for Monitoring and System Response (MSR). Reference my article titled “FMEA Effect – Mitigated or Unmitigated?” for information on when to use Supplemental FMEA for MSR. SAE J1739:2021 outlines the procedure, including determination of whether currently planned mitigation warrants a reduction in severity.

What if you are required to use AIAG/VDA FMEA Handbook or SAE J1739:2021 FMEA Standard?

The AIAG/VDA FMEA Handbook and the SAE J1739:2021 FMEA Standard do not have a column called Compensating Provisions. If you are using either of these two standards, you can use the section on Supplemental FMEA for Monitoring and System Response (MSR) to evaluate the effectiveness of the severity mitigation strategy for the item being analyzed.

My opinion is the Supplemental FMEA for Monitoring and System Response (MSR) is overly complex, and would greatly benefit from simplification.

Summary

Ensuring products are safe and reliable is why we do FMEAs. Very high severity means the consequence of failure is potentially unsafe. By properly identifying and evaluating Compensating Provisions, the FMEA team can assess the effectiveness of the severity mitigation strategies and take action to ensure that if failure occurs, the result is a safe condition.

[display_form id=415]