Nitric Acid Revamp and Upgrading of the Alarm & Protection Safety System at Petrokemija, Croatia

摘要

Every industrial production, particularly chemical processing, demands speciai attention in con-ducting the technological process with regard to the security requirements. For this reason, production processes should be continuously monitored by means of control and alarm safety instrumented systems. In the production of nitric acid at Petrokemija d. d., the original alarm safe-ty system was designed as a combination of an electrical relay safety system and transistorized alarm module system. In order to increase safety requirements and modernize the technological process of nitric acid production, revamping and upgrading of the existing alarm safety system was initiated with a new microprocessor system. The newly derived alarm safety system, Simatic PCS 7, links the function of "classically" distributed control (DCS) and logical systems in a com-mon hardware and softvvare platform vvith integrated engineering tools and operator interface to meetthe minimum safety standards with safety integrity level 2 (SIL2) up to level 3 (SIL3), accor-ding to IEC 61508 and lEC 61511. This professional paper demonstrates the methodology of upgrading the logic of the alarm safety system in the production of nitric acid in the form of a logical diagram, which was the basis for a further step in its design and construction. Based on the mentioned logical diagram and defined security requirements, the project was implemented in three phases: analysis and testing, installation of the safety equipment and system, and commis-sioning. Developed also was a verification system of ali safety conditions, which could be applied to other facilities for production of nitric acid. With the revamped and upgraded interlock alarm safety system, a new and improved safety boundary in the production of nitric acid was set, vvhich created the foundation for further improvement of the production process in terms Of improved analysis.