On the Determination of Requirements for Safety System Response Time

The article is dedicated to determining requirements for safety system response time. The safety system response time must be shorter than the process safety time so that the protection system can function efficiently. Notably, the process safety time is considered a period between a system failure and the occurrence of a hazardous event, which is an important criterion for the safe process system design. This time is unique for each system and for the «cause — consequence» pair and must be determined to ensure the efficient operation of Automated Emergency Protection Systems. Examples of similar analytical assessments of the process safety time for tube furnace coil overheating, tank overfilling, and pressure rise to critical values in the reactor are considered. Methods that help extend the process safety time in the case of a rapid growth of furnace coil wall temperature have been analyzed, i.e., changing the thickness of the coil wall, and the choice of more fire-resistant materials. A conclusion regarding the importance of the process safety time for the safety system design has been made. Establishing requirements for the safety system response time based on the process safety time helps optimize algorithms and the performance of protection system activation in order to comply with safety standards. In case the response time cannot be reduced, the adoption of changes in the design will help extend the process safety time, which allows for finding efficient solutions for the safety system functioning.