Applying Layer of Protection Analysis (LOPA) to Accelerator Safety Systems Design release_rev_88668642-7013-4fc1-9a31-ce01352cd526

Abstract

Large accelerator safety system design is complex and challenging. The complexity comes from the wide geographical distribution and the entangled control/protection functions that are shared across multiple control systems. To ensure safety performance and avoid unnecessary overdesign, a systematic approach should be followed when setting the functional requirements and the associated safety integrity. Layer of Protection Analysis (LOPA) is a method in IEC61511 for assigning the SIL to a safety function. This method is well suited for complex applications and is widely adopted in the process industry. The outputs of the LOPA study provide not only the basis for setting safety functions design objective, but also a reference document for managing system change and determining test scope. In this paper, SLAC credited safety systems are used to demonstrate the application of this semi-quantitative method. This example will illustrate how to accurately assess the hazardous event, analyze the independence of different protection layers, and determine the reliability of a particular protection function.
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