GB/Z 162-2025 Electrical safety of machinery—Assignment of safety integrity requirements—Basic rationale

Scope

This document applies to scenarios where a risk assessment has been completed for mechanical equipment or process plants in accordance with GB/T 15706, and safety-related control functions have been selected as specific hazard protection measures. This document describes the basic logic principles for assigning safety integrity requirements to selected functions. This description is generic and as independent as possible from any specific tools or methods available for assigning safety integrity requirements. The requirements can be expressed as a safety integrity level (SIL) or a performance level (PL). This document introduces the basic principles of these tools and methods when using a risk-based quantitative approach through examples. Conversely, the logic described in this document can serve as a reference for evaluating specific safety integrity assignment methods or tools, to clarify the extent to which these tools/methods adhere to a risk-based quantitative approach and whether there are deviations from this approach due to other considerations. In practical applications, the risk-based quantitative approach can be modified or replaced for various legitimate reasons, the discussion and evaluation of which are beyond the scope of this document. Typically, specific tools or methods provide justifications for deviations from the quantitative logic, which can be discussed within an appropriate framework. This document provides analysis examples of common assignment tools in the form of risk diagrams and risk matrices. This document can be used for various application modes of safety-related control functions: continuous mode, high-requirement mode, and low-requirement mode.

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