Selection of solenoid valves?
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The situation is as follows: a shut-off valve (FC) needs to be interlocked to open and interlocked to close within the SIS logic. I would like to know how to choose the solenoid valve for this shut-off valve (2/3 way?) Two Wutong? Single electronic control? Dual control? A solenoid valve? Two solenoid valves)? How to connect the gas line? The SIS requires the solenoid coil to be properly energized, but not to be energized during interlock. By the way, do these two-way solenoid valves only come in normally open (NO) and normally closed (NC) types? Is there also a type called normal excitation (NE)? I hope experts can help answer this. Thank you!
I have only used two-way five-port ones; I don’t know much about the others
Is there any priority between opening and closing this interlock? ? ?
There are no priority restrictions on interlocking open and close
The interlock status is closely related to the fault status; the poster should definitely pay attention to this advice. As for whether it will be two three-way or five-way valves, as well as dual solenoid valves, those are the next steps to address.
Is there a strong connection between the interlock status and the fault status? What does that mean? Is it that the FC valve can only be interlocked to close, but not to open? What should be done if the process requires the FC valve to open in interlock mode? @backhamm1982
It should be an FO valve in terms of design
To implement an FC cut-off valve, the valve must be set to open when there is air flow, with the solenoid valve installed in the air line. The fail-safe mode maintains a power supply; when there is power, the solenoid valve is in an open state (which is why NC is chosen), the air path is open and the valve is open. At this time, the signal sent to the solenoid valve is 1, causing the interlock to turn on ； Similarly, when the signal to the solenoid valve is 0, it shuts down; the solenoid valve loses power, the air path is closed, and the valve is closed ； This ensures that the valve closes when the air path is disconnected and when the solenoid valve loses power, thereby guaranteeing safety. I hope you can understand.
We still need to consider whether it’s double-acting or single-acting
A question: In the SIS logic, the isolation valve (FC) mentioned by the poster needs to be interlocked to open and interlocked to close. I assume that the process reasons for opening and closing must be different, right? So if these “reasons” occur at the same time, is this valve open or closed? Is the same requirement applied in causal diagrams as well? For SIS interlocks, such situations are very rare.
The SIS interlock takes into account the safest stopping position; there is no need to dwell on whether the interlock is on or off – only one option can be chosen.