Representation method of SIS interlock

When representing the interlock logic of a SIS (Safety Instrumented System), logic diagrams or function block diagrams are typically used for description. When represented on a diagram, a series of symbols and lines are used to depict the control and safety logic. Based on what you’ve described, you have a reactor bed with 12 temperature measurement points, and it features two different interlock logic systems: 1. A 300-degree interlock using 12 choices of 3: this means that if the temperature at any 3 of these measurement points reaches or exceeds 300 degrees, the interlock mechanism is activated. 2. Interlock at 320 degrees for any one point: This means that when the temperature at any one temperature sensing point reaches or exceeds 320 degrees, the interlock mechanism is activated. To represent these logic relationships in a diagram, the following steps can be followed: 1. Use a sensor symbol for each temperature measurement point, and label it with the corresponding measurement number. 2. For the 300-degree interlock in a 12-to-3 configuration, it can be represented as 12 inputs passing through logical “comparison” function blocks (to determine whether the value is ≥300 degrees); the outputs of these 12 comparison blocks are then connected to a “voting” logic block, using a 3oo12 logic scheme (i.e., an output signal is generated when 3 out of the 12 meet the condition). 3. For any one case where the interlock is triggered at 320 degrees, a logical \"OR\" gate can be placed after each comparison block; the outputs of all these comparison blocks are connected to this \"OR\" gate, so that a signal will be generated as long as one of them meets the condition. 4. An alarm value of 290 degrees may require a separate setup, providing an alarm output for each temperature measurement point. 5. All safety interlock output signals (300-degree interlock and 320-degree interlock) can be combined into an AND gate or an OR gate to determine the final action to be taken (such as emergency shutdown, alarm, etc.). Please note that the actual representation method may vary depending on the specific engineering standards of the application and the drawing tools used. Below is an example of a simplified logic block diagram: ------| ------| . . | . . |------(interlock action) . . | ------| ------| ------| . . |------(interlock action) . . | ------| In the above example, each Temp1 to Temp12 represents a temperature measurement point, and the respective elements represent the logic for comparing these values with set points. The 3oo12 Vote mechanism reflects a 12-to-3 voting logic, meaning that activation is possible as long as any one of them triggers. The above are the basic logical representation methods; actual drawing design should comply with the standards and specifications of your project. You can consult the project’s process control engineer or refer to the relevant engineering design standards to ensure that your SIS interlock logic is represented accurately. .

Here is a method of showing two options out of three in images for your reference

Thank you. Is what I’ve shown in my diagram reasonable?