Definition:
RAM is a concept that refers to Reliability, Availability, and Maintainability. It is not a formally defined term in IEC 61511 or IEC 61508. Instead, it is a general reliability engineering concept that is often referenced informally when discussing performance assumptions that underpin functional safety calculations.
While RAM itself is not a safety integrity measure, its underlying elements—failure rates, repair times (MTTR), and availability assumptions—are design inputs into SIL verification inputs and lifecycle decisions.
Key Points:
- RAM is a concept in reliability engineering, it is not a word used directly in functional safety.
- Some aspects of IEC 61511-1 would be considered RAM. Things like failure rates, MTTR, and SIL verification.
Example:
Two pumps are compared for a non-safety BPCS service based on uptime and repair time. This is a RAM decision with no functional safety implications.
See Also: failure rate, MTTR, OREDA
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