Let’s take a look at this interlock logic diagram and discuss it
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Everyone, please take a look at this interlock logic diagram to see if there are any issues. There are two points I don’t understand: 1. Why is the interlock status for XB-01 and ES01.02 in the closed state? Shouldn’t a hard fault cause the interlock to be disconnected? 2. The interlock status between the valve and the pump is disconnected; why is S1 R used instead of R1 S? Please, experts, help me understand this
1. Power can be supplied to the solenoid valve only when XB01 and ES01.02 are closed; it is not involved in any logic operations and represents a hard-wired connection, with interlock triggered upon disconnection； It’s exactly the opposite of what logic would suggest ； 2. Reset and set are selected as required. There is a difference in priority when both the set ’S’ and reset ’R’ signals are 1. When both the set and reset signals are 1, the output of an RS flip-flop is 1; the set signal takes precedence ； When both the set and reset signals are 1 for an SR flip-flop, the output is 0; reset takes precedence. A set-priority flip-flop is a latch with set priority. The output is true when both the set signal (S1) and the reset signal (R) are true. A reset-priority flip-flop is a latch with reset priority. When both the set signal (S) and the reset signal (R1) are true, the output is false. The command to set the flip-flop first (SR) and the command to reset the flip-flop first (RS) can be understood as SR indicating priority for setting.
The interlock trigger state should be off； The intermediate OR gate should be modified to an AND gate ； When interlocking occurs, both R1 and S are 0, preventing any action from being carried out ； The 2 emergency stop buttons should perform an AND gate with the instrument in front of the RS flip-flop.
In my opinion, an emergency stop should be a normally closed switch, not a normally open one. It should be fail-safe. Therefore, a normally closed contact should be selected.
This post was last edited by jlshnlhj on 2022-3-19 09:57. Let’s first see what the output of s1 r is when it is running normally Q'?
The interlock definitions for SIS systems and DCS systems are different; a normal SIS signal is 1 (on), while an abnormal one is 0
This diagram is a bit messy and has the following issues. 1. The most obvious mistake is drawing the reset and emergency stop contacts as the same. 2. The emergency stop button must be placed in the logic circuit first; it cannot be placed after the output, otherwise how can wiring be done after the relay outputs? ? 3. Although XB01 is named as a bypass permit, it actually functions as a bypass; this aspect isn’t reflected in its name. It seems to serve as a global bypass, and such a setting is not recommended. It’s best to add a soft bypass as well.