Help with logic diagrams
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This post was last edited by Horse I see, I see on 2019-2-13 at 14:50. Please help check whether this SIS logic is correct There’s something that doesn’t seem right... Please explain
So where do you feel something is wrong?
This post was last edited by Horse I see, I see on 2019-2-13 at 15:08. During interlocking operation, the normally open contacts close, generating a signal with a value of 1; after inversion, the output becomes 0. But why do the normally open contacts open when the relay operates? Is it a live interlock or a dead interlock? Should a normal SIS system not be fail-safe? The normally closed contact of the interlock is open
You need to understand the process flow. If the SIS valve related to temperature is an FO valve (usually an internally cooled valve), then when the conditions are met, the solenoid valve loses power and the valve opens; if what’s related to temperature is the feed valve of the reactor (FC), then when the conditions are met, the solenoid valve loses power and the valve closes. The configuration of the SIS system must take into account both the process flow and the selection of valves
The relays and solenoids are normally powered; therefore, when interlocking occurs, both the relays and solenoids lose power, causing their normally open contacts to disconnect
It seems there’s no problem; interlocks are not triggered in a faulty condition