Process quality and risk can described by
- Reliability: does the system perform as expected, what is the probability of undesired events?
- Availability: is the system available, what is the fraction of 'up-time'?
These goals may be opposite and certaintly are related
- The safest system is a system that does not operate at all (you can not make mistakes if you do nothing).
- The highest 'up-time' fraction is reached when you do not care for the quality of the product.
By performing a quantitative fault tree analysis (FTA) of the system, the probabality of failing the functional mission of the system (reliability, availability), is calculated. Consequently, importance analysis shows the parts that have the biggest influence on these probabilities and therefore need the most attentian in design and maintenance. These parts can be prioritized for optimization if the overall probability of failure needs to be lowered or the availability of the system needs to be increaded. It is also possible to assess whether the relative contribution to unreliability (and unavailability) of all safety systems are consistent with their relative capital and operational expenditures. Thus, FTA provides companies with a tool to optimize the quality as well as the cost-effectiveness.
When and where necessary, I work together with Cornelis P. Willig, a very (internationally) experienced risk analyst (www.diac.nl).
The approach constists of three major phases:
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Qualitative / semi-quantitative prioritization of process parts to be included in the FTA, e.g. by
- Failure Mode Effects and Criticality Analysis (FMECA)
- HACCP (Hazard Analysis Critical Control Point)
- Qualitative Fault Tree Analysis (FTA) - linking all events into one tree
- Assigning failure models and data to the events (from public data or specific maintenance data)
- Quantitative FTA
Presentations
2009 Top of page
- Van Lieverloo, J.H.M., Willig, C.P., A., Fox, M.B. and Wells-Bennik, M.H.J. (2009). Estimating the probability of undetected failure of pasteurization process control using Fault Tree Analysis. Proceedings 6th International Conference of Predictive Modelling in Foods, Washington, USA, 8-12 September
Download
2008
- Van Lieverloo, J.H.M., Wübbels G.H. and Willig C.P. (2008) Quantitative Risk Assessment and Fault Tree Analysis to quantify the balance of reliability, availability and costs of water treatment facilities. IWA – Waternetwork Conference on Industrial Water Treatment Systems, Amsterdam 1-3 October.
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