Overview
ISO/TR 12489:2013 - Petroleum, petrochemical and natural gas industries - Reliability modelling and calculation of safety systems - is a Technical Report that provides guidance to close the gap between state-of-the‑art methods and practical application of probabilistic calculations for safety systems in oil & gas. It focuses on modelling and calculation of random failures in safety systems (including safety instrumented systems), and describes analytical and computational approaches rather than prescribing mandatory design rules.
Key topics
ISO/TR 12489:2013 covers a broad set of reliability modelling and calculation topics, including:
- Modelling frameworks and an analysis workflow for reliability and safety-calculation tasks.
- Approaches for probabilistic calculation:
- Analytical formulae (low-demand/on‑demand mode)
- Boolean approaches: Reliability Block Diagrams (RBD), Fault Tree Analysis (FTA), Event Trees and sequence modelling
- Markov models (multiphase Markovian analysis)
- Petri nets for complex sequential and concurrent behaviours
- Monte Carlo simulation techniques
- Failure classification, safe vs. unsafe failures, dependent and common‑cause failures, and human factors considerations.
- Reliability data: sources, collection, required parameters, and handling of numerical uncertainty.
- Typical application examples (single channel, dual channel, redundant architectures, multiple safety systems, emergency depressurization).
- Extensive informative annexes on modelling details, common‑cause failures, human factors, and numerical uncertainty handling.
Note: elementary hazard analysis methods (PHA, HAZID, HAZOP, FMECA) and non‑random failures are out of scope, although their outputs feed the probabilistic analyses discussed.
Practical applications
ISO/TR 12489:2013 is aimed at enabling robust probabilistic assessment of safety systems to support:
- Safety integrity evaluations and SIL assessments for safety instrumented systems (SIS)
- Quantitative risk assessment (QRA) and consequence analysis
- Design verification of redundant and multi‑layer safety architectures
- Reliability-centered maintenance planning and test interval optimization
- Assessing effects of dependent and common‑cause failures on system safety
Who should use it
- Reliability and safety engineers in the petroleum, petrochemical and natural gas industries
- Process safety analysts, asset integrity and maintenance managers
- Consultants performing probabilistic safety assessments (PSA), FTA or reliability modelling
- Regulators and auditors seeking guidance on probabilistic calculation methods
Related standards
ISO/TR 12489:2013 complements other ISO/TC 67 reliability standards such as ISO 14224 (reliability and maintenance data collection) and ISO 20815 (production assurance and reliability management), providing targeted guidance for probabilistic modelling of safety systems.
Keywords: ISO/TR 12489:2013, reliability modelling, safety systems, petroleum, petrochemical, natural gas, probabilistic calculations, fault tree, reliability block diagram, Markov, Petri net, Monte Carlo, common cause failures.