The oil/gas, chemical, petrochemical, food, power, papermaking and other process industries consist of numerous equipment and unit operations, thousands of control loops, and exhibit dynamic behavior. Chemical process plants are subjected to different types of process risks in daily operations, which include risks due to reactivity, toxicity and mechanical hazards, fire and explosion risks etc. Failure to manage or minimize hazards can result in serious incidents. Therefore, it is very important to identify hazards, perform risk assessments, and take proper initiatives to minimize/remove hazards and risks; else a catastrophic accident may result. Dynamic characteristics such as stochastic processes, operator response times, inspection and testing time intervals, ageing of equipment/components, season changes, sequential dependencies of equipment/components and timing of safety system operation also have great influence on the dynamic processes. Conventional risk assessment methodologies generally used in oil/gas and petrochemical plants have limited capacity in quantifying these time dependent characteristics. Therefore, it is important to develop a method that can address time-dependent effects in risk calculation and provide precise estimation. This study proposes a risk assessment methodology for dynamic systems based on Bayesian network, which represents the dependencies among variables graphically and captures the changes of variables over time by the dynamic Bayesian network. This study proposes to develop dynamic fault tree for a chemical process system/sub-system. Then a procedure to map the developed dynamic fault tree to map into the Bayesian network and the dynamic Bayesian network is provided to demonstrate the dynamic operational risk assessment methodology. A case study on a level control system is provided to illustrate the methodology's ability in capturing dynamic operational changes in process due to sequential dependency of one equipment/component on others.

https://pscfiles.tamu.edu/symposia/2014/abstracts/046_Shubharthi%20Barua.pdf

Bayesian network based dynamic operational risk assessment

The DYLAM approach for the dynamic reliability analysis of systems

The dynamic logical analytical methodology (DYLAM) modeling and analysis techniques are discussed, and its principal features are compared with those of the fault tree technique for reliability analysis. The study is performed with reference to the auxiliary feedwater system of a 1300-MW (electric) pressurized water reactor plant. The results reveal the advantages that can be obtained by modeling dynamic processes by DYLAM, especially when dealing with operator interventions in incident control and mitigation.

Dynamic logical analytical methodology versus fault tree: the case study of the auxiliary feedwater system of a nuclear power plant

On the Use of Non-Coherent Fault Trees in Safety and Security Studies

Selected published literature on chemical-system reliability is reviewed. The literature is classified into several categories. These categories include: reliability prediction and analysis; reliability/maintenance/safety; risk analysis, control and assessment; fault diagnosis and propagation; failure analysis and prevention; failure data and analysis; reliability optimization; human reliability; application of reliability engineering to process plant industries; availability analysis; and life-cycle cost and economy. The literature is collected mainly from major journals and conference proceedings. An extensive list of references is presented. >

Chemical-system reliability: a review

Reliability analysis of chemical processes by the DYLAM approach

Safety analysis of hazardous processes requires the use of models to simulate dangerous transient conditions and to assess the availability of the relevant mitigating and protective systems. As this article shows, these two needs can be fairly well satisfied by the application of DYLAM, which is able to take into account the dynamic aspects of the interaction between time‐dependent operational variables, control and protection systems and human interventions at both nominal and failure conditions and, therefore, presents significant advantages with respect to the normally utilised fault trees/event trees.

G. Reina

Papers

Reliability analysis of chemical processes by the DYLAM approach

Application of Dylam to the Safety Analysis of Chemical Processes