Could someone experienced take a look and tell me if this interlock analysis is correct?

S R Q 0 1 0: The basic principle is that whenever the crusher stops, the feeder also stops. If the crusher is not stopped and the feeder sends a fault signal, either by pressing the stop button or when the value displayed on the on-site instrument reaches the interlock value, the feeder will stop. The feeder 1 1 0 has no fault signals, and the crusher is also running; at this point, if the button is pressed or the value displayed on the local instrument reaches the interlock value, the feeder stops. The feeder 1 0 1 has no fault signals; the crusher is running, no button was pressed, and the values on the on-site instruments are normal, so the feeder continues to operate. The 0 0 Keep feeder has a fault signal; the crusher is operating normally, the button has not been pressed, and the values on the on-site instruments are also normal, so it remains in its previous state. But I have a question about your logic: when it changes from 1 01 to 0 0K, it indicates that there is a fault signal from the feeder. Yet since the output remains at 1 due to the Keep setting, isn’t it still possible to start the feeder? Even though an alarm is triggered when there is a fault in the feeder, I don’t think this makes much sense

There is a problem with this logic: when the feeder is operating normally, the on-site buttons and monitoring instruments all display normal values, with S set to 1, R set to 0, and Q outputting 1. Thus, the signal allowing the feeder to start is 1 while the stop signal is 0. When a fault signal occurs in the feeder, S becomes 0, but R remains 0; Q retains its value from the previous cycle, so the signal allowing the feeder to start stays at 1 and the stop signal remains at 0, meaning the feeder does not stop. The logic can be modified by introducing the feeder failure signal to terminal R, just before the signal is fed into the OR gate.

Personally, I think it would be better if you replaced the feeder fault signal in the first diagram with a reset button, and removed the NAND gate on that circuit as well. It is 1 when the button is pressed, and it becomes 0 when it automatically releases after being pressed for a while. Are you using Yokogawa’s DCS system? For the button, use %SW; the automatic lowering function will be implemented by writing the relevant logic in LC64. In the second diagram, the feeder is allowed to start while the crusher is in operation. But if the local instrument reaches the interlock value or the local stop button is pressed, wouldn’t that result in a situation where both starting and stopping are permitted?

In the second diagram, as you said, there will be a situation where both starting and stopping are allowed, but can’t this be achieved on the electrical side? Allowing startup to proceed only upon receipt of a start signal makes sense, right? It shouldn’t interfere with the stop signal, right?

I’m sorry, I work with instruments; I don’t know much about electrical aspects. But I feel that when the values shown on the on-site instruments reach the interlock value, it is a condition for shutting down the machine; this shutdown interlock is there to protect the machine. According to the logic of this 2-diagram, there will be times when startup is allowed as well as times when shutdown is required; it can therefore be inferred that there will be situations where, even though the values read by the on-site instruments have reached the interlock value, startup is still permitted. At this point, if someone accidentally sends the start signal (is your start signal controlled simply by a button, or does it involve some logic as well?) ), because by separating the start and stop signals in the electrical system, the machine can start properly, and it won’t get damaged due to excessive or insufficient pressure, temperature, or anything else? And what if, by chance, there were workers working near the machine at that time? In my opinion, the conditions under which a machine is allowed to be started should include complete calmness at the site.

1. Nowadays, the starting and stopping of large electrical equipment require two signals, each in a different electrical circuit. Because there is also related protection for electricity. 2. When designing interlocks in general, a hold-type design is considered; after an interlock action occurs, confirmation is required before it can be reset and put back into use, in order to prevent accidental actions. 3. The fault signals from electrical equipment are usually generated by the contacts of the motor stop contactor; therefore, once a fault signal is detected, it is sufficient to prevent the motor from starting, and there is no need to shut down the motor altogether. However, the specific approach depends on the electrical circuit.