Funnel Risk Graph Method in the Design of Integrated Control and Safety System

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Gabriel, Angelito (2018) Funnel Risk Graph Method in the Design of Integrated Control and Safety System. PhD thesis, Victoria University.


With the emergence of oil and gas industries such as the LNG industry in Australia, e.g., the Chevron’s US$54B Gorgon and Wheatstone projects, Inpex’s US$34B Ichthys, Shell’s US$12.6B Prelude FLNG, Origin’s $24.7B APLNG’s projects, to name a few, and other related industries, it is inevitable that these industries need to utilise risk analysis techniques during the development and application of their Safety Instrumented System (SIS), in order to efficiently and safely conduct its business, and for industry compliance. Currently, evaluation and design of integrated control and safety systems (ICSS), particularly the SIS are often cumbersome, time consuming and complex considering a lot of Standards and Regulations to follow. These systems are mission and safetycritical systems such that the development and execution must be carefully planned and traceable to certain Standards and Regulations but needs to be costefficient. To address this impending concern, this research project will focus on the development of an application of a more cost-effective, simplified and enhanced approach for the design and evaluation of Safety Instrumented Systems (SIS) called the Funnel Risk Graph Method (FRGM). Although risk graph methods are commonly used in industries, the FRGM is unique in a way that the approach is presented as a screening tool or initial pass, before a more detailed analysis is carried out. Instead of subjecting all Safety Instrumented Function (SIF) one-by-one to a much complex traditional assessment process, the FRGM is used as a funnel. If the assessed safety-related system received Safety Integrity Level (SIL) allocation of greater than SIL 2 during the initial pass then a semi-quantitative or a quantitative method as a ‘final pass’ should be conducted, or the multidisciplinary assessment team reached an agreement to justify the ‘second pass’ or pose a high Equipment Under Control (EUC) risk. Based on the preliminary results, it is expected that significant economic benefits can be achieved. Likewise, compliance will become more practicable and standards more useful, resulting to an equal degree of functional safety as compared to the traditional approach yet resource utilisation is efficient. Further testing and analyses will be conducted to quantify the benefits of FRGM. Real-life case studies utilizing industrial SIS devices will be presented to demonstrate the benefits of this approach. In contrast with other complex schemes commonly used for safety assessment, the proposed FRGM gives benefits such that it is straightforward in steps and resource-efficient. While safety is aimed at protecting the systems from accidental failures to eliminate or minimize hazards, security is focused on protecting the systems from deliberate malicious attacks. They share the same goal – protecting the SIS from failing. Industry cybersecurity has become more critical these days, and to address such concern, risk assessment for the cybersecurity of SIS is proposed to be integrated in the assessment process using a proposed framework, as part of the enhanced process.

Additional Information

Doctor of Philosophy (Electrical and Electronic Engineering)

Item type Thesis (PhD thesis)
Subjects Historical > FOR Classification > 0906 Electrical and Electronic Engineering
Current > Division/Research > College of Science and Engineering
Keywords safety instrumented systems; integrated control and safety systems; industry compliance; risk graph method; safety assessment; cybersecurity
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