Installation of cut-off valves for liquefied gas cylinders in major hazard sources
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Criteria for identifying major potential hazards in production safety for chemical and hazardous chemicals manufacturing and operating units: 5. Hazardous chemicals storage areas that constitute level 1 or level 2 major hazard sources lack an emergency shutdown function； The hazardous chemical storage areas that constitute Class I and Class II major hazard sources involving toxic gases, liquefied gases, and highly toxic liquids are not equipped with independent safety instrument systems. I understand that a shut-off valve needs to be installed; either DCS or SIS can be used. Since liquefied gas is a type of liquefied gas, it needs to be incorporated into the SIS system ； According to the Emergency Management Bureau, the first sentence implies that a shut-off valve is required in the DCS, while the second sentence indicates that a shut-off valve is needed in the SIS; therefore, 2 shut-off valves are required in total
All the suggestions given are correct. First, an emergency shut-off valve needs to be added at the base of the storage tank; this can be integrated into the DCS system. Second, to meet the requirements of the second point, not only must a shut-off valve be added, but also an independent SIS system is required. In that case, this isolation valve needs to be evaluated and classified. As a SIS valve with an independent function, it is not used as a switch for normal operations; the SIS valve serves only to perform the functions of emergency shutdown or opening when the process parameters exceed those set by the DCS, or in emergency situations. Under normal conditions, it remains in its original state. To close or open the root valve of the storage tank, either a manual valve or an automatic valve can be used – thus there are two valves in total. The emergency isolation valve falls under the category of SIS valves. This is merely for reference; choose the approach that works best and modify those that don’t.