Feedback issues of pneumatic cut-off valves in SIS
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For the emergency shut-off valve in the SIS interlock, is it necessary to monitor the valve position feedback signal? If so, should it be sent to the SIS or the DCS?
It is necessary to monitor the feedback signal; if the feedback signal is not involved in interlock functions, it goes to the DCS, while if it relates to interlock conditions, it goes to the SIS.
Generally, cut-off valves require valve position feedback.
That’s right; the interlock signals are definitely triggered by the SIS. However, during normal operation it is also necessary to monitor the valve position feedback. Since it’s not possible to carry out monitoring through the SIS system during normal production, in most cases the signals are sent to the SIS system first and then transmitted to the DCS system
Can I go directly to DCS? In this way, SIS saves two sets of DI points
Valve feedback can be sent directly to the DCS, but the control function must be handled by the SIS. If it is desired for the DCS to be able to operate as well, then the DCS side must also control the SIS system to issue commands
:If DCS can control SIS, then what kind of SIS is it still called? SIS is an independent safety interlock system; it has a higher level than DCS and constitutes an independent operating system, with computers that cannot be shared with those used in DCS. It’s better to enter this feedback into SIS, as there are also displays on SIS; it’s not possible to not be able to see the current status of the valve positions there. Should we only focus on switching it on and off without caring about the results? Definitely not; it’s certainly inappropriate to just kill without taking care of the burial. The signals from the SIS must be transmitted to the DCS, so it’s still possible to view the DCS screens; however, they can only be viewed and not manipulated.
Enter the SIS system; high priority.
The priority of SIS is higher than that of DCS; once the SIS interlock is triggered and SIS is not reset, the DCS side cannot take control. According to current regulatory requirements, it must be completely independent; if the process requires the use of on/off valves during production, then valves must be installed over those valves
If those involved in the chain want to use SIS DCS for monitoring, that would be great.
If those involved in the chain want to use SIS DCS for monitoring, that would be great.