Abstract: The process signed directed graph (SDG) model represents the cause and effect linkages to connect the fault origin to the observed symptoms of the fault. Fault analysis using the process SDG-based model is based on directed graph qualitative reasoning strategy. In this paper，the elementary conception and improved arithmetic of SDG-based fault analysis are introduced. Finally，a case study of a chlorine release accident occurred in a vinyl chloride plant is given.

摘要： 基于符号有向图（signed directed graph，SDG）的化工过程模型可以表征过程故障与故障源之间的因果关系，SDG故障分析方法通过有向图定性推理技术实现故障诊断。本文简要介绍了SDG故障分析的基本概念，并对Iri算法^[1]中故障源的搜索步骤提出了部分改进，并进行了实例验证。最后，利用SDG故障诊断方法对某化工厂的氯气泄漏事故的故障传播进行了分析研究。