Issues related to safety instrument redundancy configuration

Your question shows that you fundamentally do not understand why safety instruments need to be redundant. The redundancy in SIS isn’t something that can be implemented just because you say so; it is based on certain criteria. It is determined through HAZOP analysis and LOPA analysis, and then it is decided whether redundancy is needed based on the SIL level of the instruments themselves – whether it should be a two-out-of-two or a three-out-of-two configuration. It’s not as simple as saying you need redundancy and just adding another instrument. So, to answer your question: is it possible to use three sets of differential pressure and level sensors? Sure, does it meet the standards? Who knows. . . .

The 2nd floor is clearly stated in terms of SIL certification. In terms of usage, the same level gauge can be used as a redundant instrument. I remember that the standards require that instruments measuring the same parameter use at least instruments based on different principles, presumably referring to on-site displays and remote transmission displays. On the other hand, there are no specific regulatory requirements for chain remote transmitters to use instruments based on different principles. Those who want to know more can provide additional details

Putting everything else aside, in which specification did you see the requirement for different measurement principles? Please do not arbitrarily apply outdated or irrelevant standards

I have a question: regarding safety instrument redundancy, for things like level measurement, if a DCS is equipped with one set of differential pressure transmitters, and redundancy is required for safety instruments, can three sets of differential pressure transmitters be used for level measurement? The specifications do not state that it is not allowed; two sets can be integrated into the SIS, and the tank should have three sets of mounting holes. Safety instruments do not necessarily need to be redundant; of course, you can opt for redundancy in accordance with requirements outlined in 50770, or you can choose the appropriate design based on SIL verification calculations. If redundancy is required, what is the number of copies needed? 1oo2 provides high reliability but low availability, while 2oo2 offers high availability but low reliability (safety). Neither of these approaches is ideal; 2oo3 provides a balance between availability and reliability. A balance between availability and reliability, with 1oo1 being the next option. Generally, 1oo1 is sufficient for SIL1, while 2oo3 is recommended for SIL2 (of course, this depends on the RRF value if it is not taken into account)

Safety instruments do not necessarily have to be redundant; it is necessary to determine the SIL level of the circuit based on a HAZOP analysis, and then decide whether redundancy is required.

Maybe I didn’t make myself clear; what I’m asking is whether it’s possible to use the same principle

I didn’t explain it clearly either; it has been determined to be level two. The experts suggest using redundancy – having two or three units is considered redundant, as it’s possible to use the same principle in all of them

Well, the Safety Instrumented Systems specifications don’t mention this; is it possible to use requirements based on the same principle?

SIS is a Level 2 system; experts require redundancy. I’m not sure whether to set two or three instances. How is this calculated?