Difference between SILA and SIL0 in SIL classification
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Let’s discuss the differences between SILA and SIL0
SILA and SIL0 are two different levels of Safety Integrity Level (SIL). SIL is a way of expressing industrial safety standards; it refers to the level of capability of a safety-related system to carry out specific safety tasks with a certain failure rate within a specified time frame. The SIL range goes from SIL1 to SIL4, with higher levels indicating greater system reliability. SILA refers to a safety integrity level of \"A\", with the SIL value typically falling between SIL1 and SIL2. And SIL0 refers to the absence of a safety integrity level. Therefore, SILA is more reliable than SIL0 and can provide a higher level of security. In summary, there is a significant difference between SILA and SIL0 in terms of safety integrity level; SILA is safer and more reliable than SIL0. -
Bro, where does this claim come from? Are there any specific references?
SIL0 indicates that no safety integrity level requirements are applicable, meaning that the relevant scenario meets the acceptable risk criteria and no additional SIF is needed； SILA indicates that there are no special security requirements, which means that the scenario in question does not meet the acceptable risk standards; there is still a gap of 0–0.1 (PFD) that needs to be covered by other IPLs.
I agree with the view from floor 5; neither SIL0 nor SILa needs to be included in the SIS.
Both SILA and SIL0 are SIL rating results, not levels. SILA indicates that the risk has not reached an acceptable level. For example: if the required risk level is SIL3, then SIL1 and SIL2 both fall within the scope of SILA ； If the required risk level is SIL4, then SIL3 also falls within the scope of SILA. SIL0 indicates that the average failure probability of the function is greater than that of SIL1.
International standards only define SIL1-4; I’m not sure who came up with SIL0. Here we see SILA as well – impressive. When performing process safety analysis for protection layers, a standard DCS may not be sufficient; another system is needed for protection, but a SIL1 level is not required. In plants that already have a SIS system, it is common practice to include such circuits within the SIS as a second system in order to meet these protection requirements, without the need to conduct any calculations for those circuits. Since the requirement is lower than SIL1, some call it SIL0.
Since SILA is included in the analysis report, not including SIS probably means the experts are reluctant to do the inspection. Some companies conduct HAZOP analyses without including SILA, while others prefer to include it; there is no uniform standard, which creates chaos. As a result, many SILA values are established – not including them in the SIS system seems wrong, but including them leads to waste.
SILA only appears in the IEC61511 diagrammatic approach, and SIL0 has no clear origin at all; in short, it’s just made up: lol. One can only follow the opinions of certain experts, otherwise it amounts to challenging authority.