A DCS isolation valve is installed at the outlet of the liquid chlorine storage tank; is it necessary to add an SIS isolation valve as well?
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For the outlet of the 100-cubic-meter liquid chlorine storage tank at our company, only a DCS isolation valve was installed based on the results of the Hazop analysis; however, according to Order No. 40, a separate SIS system is required. Since we moved the isolation valve to the SIS system, it does not meet the requirements, right? Is it required to install separate SIS shut-off valves and DCS shut-off valves for export?
In accordance with Order No. 40 and general safety engineering practices, it is recommended to install a separate SIS isolation valve at the outlet of the liquid chlorine storage tank. Although DCS systems enable remote control and monitoring, they are ordinary automation control systems that may fail to function properly in emergency situations for various reasons; whereas SIS systems offer higher reliability and security, allowing for rapid response and shutdown in emergency situations. Under the specified security levels and risk assessment categories, dual backup measures can enhance the security and reliability of the system. Therefore, it is recommended to install an SIS shut-off valve at the outlet of the liquid chlorine storage tank to enhance the safety of the system. .
It is necessary; DCS serves production operations, while SIS serves safety. The SIS shut-off valve is normally open and shuts off automatically in case of an anomaly. The DCS does not need to control the switches on its own based on production requirements