An overall knowledge-based methodology for hazard identification: Results from the TOMHID-project

The objectives of the TOMHID project were the development of an overall methodology to provide assistance and guidance in hazard identification and screening at the plant level, and to cover the different aspects of a socio-technical system important for successful safety management. This methodology was to be implemented in a computer tool. The TOMHID methods are intended to be the first stage in the hazard identification process, to identify critical areas for safety and the need for further analysis. A set of methods based on functional modelling was developed which could be based on the plant description. The goal of functional modelling and decomposition is to prepare a systematic and comprehensive description of a process plant with reference to hazard identification. The aim is to represent the plant as a socio-technical system in a hierarchical, object-oriented manner. In the first step of the TOMHID hazard identification process, Concept Hazard Analysis (CHA) is used to identify the main hazards that the process plant might generate or face. The next step in the TOMHID approach is to prepare descriptions of the incident scenario(s) that can lead to the identified hazards, and to investigate the immediate and root causes of the identified errors, failures and disturbances, especially those that concern the impact of management on plant safety. Selected incident scenarios are then analyzed with a new method called MIMIX (Method for investigating management impact on causes and consequences of specific hazards). The TOMHID approach is to identify those deficiencies which are important for or critical to safety, using examples of real conditions which promote errors and violations that might have an impact on incident scenarios. Two benchmark trials were performed to test the TOMHID methods. They were carried out in a petrochemical plant and in a small oil refinery. The TOMHID methodology was developed for use in operating plants and plants at a pre- operational stage. The trials in operating plants have demonstrated that these basic aims have been met, because the development of a functional model, the execution of the CHA and the development of scenarios are similar whether the plant is operational or still in the pre-operational phase. The use of MIMIX in operating plants has been described, and the method might be useful in plant design while operating instructions are being planned. It also might be helpful in establishing safety-related management functions during the commissioning of a plant.