Issues regarding SIL level certification for instruments in SIS systems
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I have a question: after performing a LOPA calculation, it is determined that a certain SIS interlock circuit belongs to the SIL1 category. Do all instruments in this SIL1 circuit need to have an SIL1 certification as well? I really seek advice!
The control system requires certification. Detection instruments and actuating instruments are not required to have SIL certification; it is sufficient as long as the loop calculation meets SIL1 standards.
Detection instruments and actuation instruments are not required to have SIL certification; how is the circuit calculated? Based on on-site experience with instruments? (Is the instrument failure rate determined through experience? ) Thank you!
Yes. I’m not sure about the specific values yet, as I’m still learning this area*. However, SIL certification is not mandatory; ordinary tables also contain data values, but the data for certified tables has more solid backing. This is a state-run canteen; the beef we use has been inspected by the **quarantine agency, so there can be no problems with it. Haha. One day, the canteen didn’t want to have it inspected by the quarantine agency; it was more expensive, so we decided to buy it from the village. It was black water buffalo raised by my aunt’s family, and although it hadn’t been inspected, its quality and quantity were excellent. :lol
If the people from the safety supervision agency request the calculation basis for the PFD, will they accept it in the absence of a SIL certification? I’m afraid they might cause trouble.
After LOPA calculation, an SIS interlock circuit is classified as SIL1 level; however, not all instruments in such a SIL1 circuit necessarily need to meet the SIL1 standard – for example, some instruments with a SIL2 rating can still be considered part of this circuit if they use two-out-of-one or three-out-of-two logic schemes. The final result is subject to the verification of the SIL loop.
The SIS control system requires SIL certification, but the sensing instruments and actuators do not need such certification; it is sufficient to configure them in such a way that the calculated failure probability and operational time meet the requirements of the desired SIL level. After all, the ultimate goal is to ensure that the functions of the SIS system fulfill the requirements of that SIL level. The experts responsible for drafting the national standard on this issue specifically clarified it for us.
How can the failure probability of instruments be determined? If the manufacturer does not provide the corresponding certification. I truly seek advice
This is a matter of two phases: SIL1 represents the safety requirements during the design and construction phase; therefore, the circuit components must meet SIL1 standards during construction. After construction is completed, a SIL assessment is carried out to determine whether the required SIL1 level has been achieved.
No need, but using components with SIL1 certification to build this circuit usually results in successful verification
In addition to what has been mentioned above, the PFD value also needs to be taken into consideration