Consequence
In reliability engineering and CMMS, consequence (or failure consequence) is the specific outcome or impact resulting from a failure mode, categorized by severity regarding safety, environment, operations, and economics. It determines the priority of maintenance tasks, guiding decisions on whether to prevent, predict, or accept failures based on their potential harm.
On the shop floor, consequences classify failure modes into four categories to select appropriate maintenance strategies. Hidden failures are not immediately evident and require predictive tests to detect before causing secondary failures. Safety/environmental failures cause injury, death, or environmental damage, mandating preventive tasks to eliminate risk. Operational failures cause immediate downtime, requiring rapid restoration. Non-operational (economic) failures degrade performance or increase costs but do not stop production, often managed via run-to-failure or deferred maintenance. This categorization ensures resources focus on high-consequence assets.
- Misclassifying Safety Risks as Operational: Treating a pump failure that could cause a toxic leak as a simple downtime issue, leading to inadequate preventive maintenance and potential catastrophic injury.
- Ignoring Hidden Failure Modes: Assuming all failures are evident and skipping predictive monitoring, allowing hidden bearing failures to progress until they cause catastrophic shaft destruction.
- Over-Maintaining Non-Critical Assets: Applying high-cost predictive maintenance to assets with purely non-operational consequences, wasting resources that should target high-consequence assets.
How is Consequence quantified in Risk Analysis?
Risk (R) is calculated as the product of the probability of failure (p_F) and the consequence of failure (C_F), expressed as R = p_F × C_F. Consequences are often monetized or rated by fatality counts, e.g., CC1 = 1 fatality, CC3 = 10 fatalities.
What is the difference between 'Hidden' and 'Evident' consequences?
An evident failure is immediately known to the operator, e.g., a stopped motor. A hidden failure is unknown until a subsequent event reveals it, e.g., a backup valve that failed silently and only fails when the primary valve opens, requiring specific detection tasks.
What defines a 'High-Consequence System'?
A system where failure consequences, such as loss of life or organizational collapse, are so severe that the cost of prevention is almost always justified over the cost of external failure, shifting the strategy to extreme prevention.