Can’t use a safety barrier with one input and two outputs for the SIS system, right?
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Problem description: The high pressure in the reactor (R1501) – indicated by PSHH-R1501 – triggered the interlock that shut down the feed valve XV-R1501-1. The circuit for the circulating water feed valve is classified as SIL2, and a safety barrier with one input and two outputs is used on-site. . Basis: Article 6.2.2 of the Code for Design of Safety Instrumented Systems in Petrochemical Industries (GB/T50770-2013).
Try not to launch new projects all at once. Independence
All devices on the SIL circuit are required to have SIL certification. First of all, I ask: does your two-way safety barrier have SIL certification?
SIL2 is acceptable; considering common cause failures, it might be better to keep them separate. SIL2 places quite high demands on the instruments
Well, in general they can be combined, but if everything is done exactly according to the standard optimal methods, the cost becomes too high. A SIL2 single-input two-output safety barrier will suffice; that’s what design firms do, anyway – it’s just a matter of whether it’s appropriate or not.
What’s the purpose of the other output path? Whatever it’s for, don’t use it; otherwise there could be a common cause of failure, with both protection layers losing their effectiveness. Especially in the case of SIL2, the inspection will definitely fail.
Our SIS uses a one-input two-output safety barrier, but the other output is used by the DCS; it wouldn’t work if both outputs were fed into the SIS
For a one-in-two-out safety barrier, the safety level must be met first, and then cost should be considered; if it’s two systems, that will work. Because he’s a hard point.
An expert hired by the China Chemical Safety Association deemed the safety barriers used at a certain liquid hydrocarbon chemical plant to be inadequate and demanded improvements.
Is it sufficient to use safety barriers with one input and two outputs? The high pressure signal of the reactor (R1501), indicated by PSHH-R1501, is connected to two separate safety barriers; then the outputs from these two safety barriers are connected respectively to the SIS controller that controls the feed valve XV-R1501-1 to shut it off, as well as the controller that opens the circulating water feed valve. Does this meet the requirements?
For SIL1, a one-input two-output safety barrier can be used, but according to SIL2 standards it is not advisable; safety barriers are not permitted during on-site inspections by regulatory authorities, and using a one-input two-output safety barrier would reduce the level of protection provided.