Regarding issues with the 50770 chemical process safety instrument system
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Chapter 7 [Final Components] of GBT50770-2013 states that “final components shall include control valves (regulating valves, shut-off valves), solenoid valves, motors, etc.” I have a question for the experts here: what does “motor” refer to in this context? What should be done if a pump is normally started and stopped via the DCS, but needs to be shut down urgently through the SIS system in an emergency? Can the pump motor be included in the SIS?
If the pump is to be connected to a control system, it is usually started via DCS, stopped via SIS, and interlocks are connected to SIS. There is no such situation as you mentioned.
The motor control cabinet can be designed for multi-channel control, but it’s essential that the SIS has priority
Your statement is incorrect; take a look at the design principles for SIS in 50770
Agree with the original poster’s opinion. My understanding is that the SIS sends a start or stop signal to the MCC, and in the motor control circuit, the SIS signal takes precedence
Thank you for your help. My original understanding was that both DCS and SIS could be shut down, that is, by connecting normally closed contacts in series, so that if a shutdown command is given from either location, the entire circuit will be interrupted.