Please ask the teacher to analyze the reasons for the malfunction of the safety barrier cabinet
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Dear teachers, the Honeywell SM system used in the SIS system encountered a problem yesterday: 48 safety gates, with 1 input and 2 outputs each, located on one side of a cabinet stopped working. The output from these safety gates went to both the DCS and the SIS system; both systems detected faults in those channels. It is suspected that some environmental factor affected the safety gates, causing them to fail or lose power before recovering momentarily. One side of this cabinet features an analog safety barrier, while the other side has a DO safety barrier with a base plate; the manufacturer did not provide any explanation for this. Please analyze the reasons and figure out how to solve it.
If it is: \"Fault in 48 safety barriers with 1 input and 2 outputs\", prioritize checking the power supply and ground issues. A power loss followed by an immediate restoration of power to the safety barrier could cause this situation. Is the UPS offline?
Is this kind of one-in-two-out behavior a violation of the rules? Everyone? “The safety instrumented system should not interfere with or replace the operation of the basic process control system. ” Is this kind of calculation considered intervention?
Starting with the power supply, it should be a problem with the power supply.
Typically, 24V relays (or inductive loads such as solenoid valves) do not have reverse discharge diodes; when disconnected, the induced current reverses and impacts the 24V power supply, resulting in this phenomenon； Check the wiring of the DO output board, as well as the high-current/intrinsic safety shielding and design ； If the power supply has been independently designed, then check for issues such as backflow due to a common ground.
The power supply of the SIS system should be designed with a redundant system to avoid short-term power outages
What model of safety barrier? There could be an underlying cause.