Criticality
How is criticality differentiated from RCM consequence?
Criticality in RCM is based on overall consequence of failure; higher consequence equals higher criticality, but probability is also factored in general criticality (C = S × P).
What is the standard failure rate (λ) for high criticality (safety-related)?
λ ≤ 10⁻⁹ for failures with potential injury; low criticality (inconvenience) typically allows λ > 10⁻⁶.
How is a Criticality Rating calculated in practice?
Composite score = (raw sum of characteristics / total weighted points) × 100, producing a normalized rating for each asset.
In reliability engineering and CMMS, criticality is the relative importance of an asset to an organization’s mission, mathematically defined as a function of the probability of failure and the consequence (severity) of failure (C = S × P). It is a numeric index ranking assets by risk of failure to guide strategic maintenance focus.
Criticality is used in Criticality Analysis (CA) to systematically rank plant assets for workflow prioritization, PM/PdM development, and reliability initiatives. It determines whether an asset enters Reliability-Centered Maintenance (RCM) or requires predictive maintenance; higher consequence equals higher criticality. In CMMS, criticality ratings drive work order prioritization, spare parts inventory classification (critical spares), and budget allocation for O&M. Teams use a Criticality Matrix (likelihood vs. severity) to assign levels like Very High to Very Low, with '1' as highest priority.
Over-criticalizing non-essential assets: Assigning high criticality to low-impact equipment, wasting resources on unnecessary PdM/PM and distorting maintenance schedules.
Static criticality ratings: Failing to update criticality after process changes, reliability improvements, or consequence reductions, leading to misaligned maintenance strategies.
Confusing criticality with priority: Treating daily work priority (criticalness) as equivalent to strategic criticality, causing teams to focus on urgent but low-impact tasks while ignoring high-risk assets.