Issues with chemical process alarm settings

Hello, regarding your question, the following points are provided for reference: 1. General setting principles: – Parameters with interlocks usually have clear alarm level settings: from low to high, these are “high alarm”, “very high alarm”, and “interlock protection value”. - For parameters without interlock functions, it is generally recommended to set at least a \"high alarm\". If, based on the actual risk assessment, a stronger alert is needed (but not one sufficient to trigger an interlock action), a \"very high alarm\" can also be added. 2. Relationship between the high-high alarm value and the interlock value: – For parameters with interlocks, it is generally recommended that the high-high alarm value be equal to or slightly lower than the interlock activation value, so as to alert process operators to take action in advance to prevent the system from entering interlock mode. - It is generally not recommended to set the high alarm value above the interlock value, as once the interlock value is exceeded, the interlock mechanism already activates, and at that point an alarm is no longer useful. 3. Relevant regulatory requirements for setting: – At present, there are few unified standards in China regarding the setting of alarm values for specific processes. Generally, reference is made to internal corporate technical standards, industry-recommended specifications, recommendations provided in safety assessment reports, as well as established foreign standards such as IEC 61511 for the application of safety instrumented systems in process industries, and GB/T 21109-2019 \"Functional Safety – Safety Instrumented Systems\" and other similar standards. These standards emphasize that the setting of alarm points should be determined based on process risk assessment, equipment safety limits, and safety margins, rather than simply following fixed numerical ratios or fixed numerical differences. 4. Regarding the scenario you gave as an example: If a process control parameter is set between 10–100°C, it is generally recommended to follow the principle of safety margin, setting the high alarm threshold at a value slightly below or equal to 100°C, in order to avoid alerts being issued only after the temperature gets out of control and exceeds the specified range. - If it is determined that the process permits a brief exceedance of 100°C (following risk assessment and within the limits allowed by the design and safety requirements), the high-high alarm level can also be slightly above 100°C, provided it can be demonstrated that this is explicitly permitted and deemed safe through risk analysis with regard to the equipment, the process, and operational safety. In summary, the setting of alarm and interlock values should take into account process requirements, safety risk assessments, equipment technical specifications, and safety margins, rather than being simply determined mechanically based on numerical values. .

1. Not necessary, 2. Usually consistent, 3. None, 4. Possible

In fact, automated devices and intermittent devices should be considered separately. For automated systems, it is necessary to consider issuing an alarm first and then activating interlocks, in order to address issues promptly and prevent the activation of interlocks from affecting the entire system. For intermittent operation, interlocking can be considered first

The settings vary depending on the circumstances. In the case of high reporting, it is usually just a warning without any interlock mechanism; however, when there is very high reporting, an interlock is generally implemented

For those without interlocking, consider the control requirements; the key parameters should be set to trigger high-alarm conditions； The high-high alarm threshold for interlock functions needs to be tightened further; otherwise, such an alarm is meaningless, as the interlock will already have been triggered once the high-high level is reached. The third control criterion is whether it is the normal operating range or the maximum allowable range specified on the process card; if it is the former, exceeding that range is permissible ； The second one cannot.