OCI Nitrogen wants to gain knowledge of (leading) indicators regarding the process safety performance of their ammonia production process. This paper answers the question whether indicators can be derived from the barrier system status to provide information about the development and likelihood of the major accident processes in the ammonia production process.

The accident processes are visualized as scenarios in bowties. This research focuses on the status of the preventive barriers on the left-hand side of the bowtie. Both the quality – expressed in reliability/availability and effectiveness – and the activation of the barrier system give an indication of the development of the accident scenarios and the likelihood of the central event. This likelihood is calculated as a loss of risk reduction compared to the original design. The calculation results in an indicator called “preventive barrier indicator”, which should initiate further action. Based on an example, it is demonstrated which actions should be taken and what their urgency is.

OCI氮气公司希望获得有关其氨生产过程的过程安全性能的（领先）指标的知识。本文回答了是否可以从屏障系统状态中得出指标的问题，以提供有关氨生产过程中主要事故过程的发展和可能性的信息。

事故过程可视为领结中的场景。这项研究的重点是蝴蝶结左侧预防性障碍的状况。质量（以可靠性/可用性和有效性表示）和屏障系统的激活都表明了事故场景的发展以及发生中心事件的可能性。与原始设计相比，此可能性计算为降低的风险损失。计算得出一个称为“预防性障碍指标”的指标，该指标应启动进一步的措施。通过一个例子，说明了应该采取哪些行动以及它们的紧迫性。