Please, an expert, explain the interlock in the diagram
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Background: The R8201A reactor is equipped with two feed pumps, P8201A/C, one in operation and one as a backup. The R8201A features a circulation loop that includes a cooler; this high-flow circulation is used to remove the heat generated by the reaction. There is a low-low circulating flow interlock. To trigger this interlock, the feed pump must be stopped. Could the experts please help explain the interlock marked with a red box in the diagram? Yes, is it positive interlocking or negative interlocking? How to explain that “or”, “and” and “ and” become “o or”? How can the relationship between 1 and 0 be used to explain the derivation! Thank you very much
1 interlock; this interlock value, use a bypass for an OR operation
This is illogical; it gets triggered when the signal is 0. 1 indicates interlock bypass, while 0 indicates the interlock is in use. With the ZV5309 in the on position, if the flow rate is very low, the feed pump P8201A will be shut down via interlock, and a 0% output signal will be sent to the DCS.
This post was last edited by MTO001 on 2021-8-13 at 10:47. Taking FTZLL-F5357 as an example, when the flow rate is below 42 t/h, a low-flow interlock is triggered, with the output signal being 0 (the contacts of the interlock point are disconnected). BYPASS=1 refers to the bypass switch; here it is an OR gate； When not in bypass mode, during flow interlock, the output signal is 0; it is sent to the next OR gate, and after logical selection, 0 is output to the next AND gate for logical evaluation. Through the AND gate, the output is 0, which triggers the logic to stop the pump and thus stops the pump. The ‘o’ in the middle or in front of the OR gate indicates inversion; if the signal before ‘o’ is 1, then the signal that enters the OR gate is 0. To understand logic diagrams more thoroughly, it’s best to look at logic circuit diagrams, which show open points and closed points. If the switching point is 0, it is positive logic ； If the starting point is 1, then it’s illogical.
Thank you so much! It’s amazing that you’ve written so much and provided such detailed explanations! In the diagram, I have shown the normal operation of the push function as well as the interlock condition when traffic is very low. Could someone experienced give me some guidance? I understand the interlock switching switch: when it is in use, the output signal is 0, and when it is disabled, the output signal is 1. Is that correct?