I’m not quite familiar with interlock logic diagrams; I hope someone experienced can help me understand them

At the top is an on-site remote switch; when set to remote, the normally open START contact can then be activated

In the lower left corner are the interlocks related to low liquid level, low pressure, high flow rate, and low flow rate; the normal value is 0, and an interlock is triggered when it becomes 1. On the last line, when it is set to off, there is a 10-minute delay before it can be turned on again – it’s as if the switch remains in the off position for 10 minutes without being released

The last edit to this post was made by gxgpww on 2019-1-24 at 10:20. Those with small circles represent inversion signals; many conditions must be met in order to stop the pump

I mainly can’t understand the timing part; please give me some guidance.

A rise-edge trigger delay switch has been added; for example, a 5-second rise-edge delay means that when the signal changes from 0 to 1 and remains at 1 for 5 seconds, it will trigger the output signal to become 1. If the signal drops back to 0 at any time within 5 seconds, the output will still be 0. Typically, it addresses the issue of accidental stops caused by unstable on-site signals. Such as the fuel gas line of the heating furnace, etc

How to interpret 30S and 10min in the lower left corner?

30S likely refers to the time of 30 seconds for starting the pump, or it may mean that the pump stops operating if there is a low flow rate; 10 min refers to the 10 minutes that must pass after the pump stops before it can be started again

Firstly, the interlock logic of the SIS system must comply with the principle of fail-safe operation; this principle dictates that the field switch signal ZSR should be 1 when normal, and 0 when an action is to be triggered. 30S is a pure delay signal; upon receiving the position switch signal after 30S, the pump stops. This is generally a requirement imposed on mechanical equipment to ensure its health and safety. Similarly, 10 minutes means that once the signal at this location returns to normal, at least 10 minutes must pass before restarting is allowed. As for whether this logic is correct, I can’t tell, because I don’t know what that final functional symbol actually means RS flip-flop? Or some other definition. To analyze the purpose of each step in detail, it is necessary to understand what exactly each trigger condition is, as well as what each functional block does. Conventional functional blocks such as AND, OR, and NOT are easy to understand, but some of the functional blocks in this diagram seem to not be represented in accordance with standard conventions Anyway, everything above is just my invention