SIL Allocation for Mitigation Safety Functions

TL;DR

This paper introduces a new approach for SIL allocation specifically tailored for mitigation safety functions, addressing a gap in existing methods and demonstrating its effectiveness through a practical case study.

Contribution

It proposes a novel SIL allocation method for mitigation safety functions, supported by mathematical formulation and real-world application in a tunnel safety context.

Findings

The new method effectively allocates SIL levels for mitigation functions.

Mathematical formulation ensures rigorous SIL determination.

Practical case study validates the approach's applicability.

Abstract

SIL (Safety Integrity Level) allocation plays a pivotal role in evaluating the significance of Safety Functions (SFs) within high-risk industries. The outcomes of a SIL allocation study determine the design specifications necessary to uphold the Probability of Failure on Demand (PFD) below permissible limits, thus managing risk effectively. While extensive research has focused on SIL allocation for preventive SFs, there is a noticeable gap in attention towards mitigation SFs. To address this gap, this paper discusses the shortcomings of current methods and proposes a new approach to overcome them. The principles of the proposed method are substantiated by detailed mathematical formulation and the practical application of the method is demonstrated through a case study in a road tunnel project.