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Recently, a colleague raised a question about the selection of SIL grade instruments.: For example, for SIL3, it is okay to select the corresponding level for the system, but the instruments are generally not selected for redundancy in accordance with the "Petrochemical Safety Instrument Design Code", which is the redundancy principle of Article 5.3, because the cost is too high. Colleagues wonder, this is actually incomplete SIL3, so there is no need to press SIL3. I checked the ISA 84.01 referenced in the "Petrochemical Safety Instrument Design Specification" and the part about the sensor says this. B 1.5.3 For SIL 3, identical or diverse separation between BPCS and SIS is typically needed to meet the required safety integrity. It is not as clear as the "Petrochemical Safety Instrument Design Code" says. Please tell me, what kind of isolation does identical or diverse refer to? This post was last edited by emir001 on 2007-12-27 11:00 ]
This is what the owner is like. Sensors should generally not be shared between BPCS and SIS, but sensors can be shared if there are other stable protection implementations other than interlocking (such as bursting discs, etc.). When there is no sharing, it is usually a redundant design of two sensors and logic solver, and there is a difference between identical and diverse. Identical means that the two sensors used are of the same type, manufacturer, and model. Diverse refers to different manufacturers and types. The same, there will be the same failure mode, there may be the possibility of simultaneous failure. Different modes may have different performance issues. However, they must meet safety integrity requirements.