What is the SIL level in instrumentation?
What is SIL Level in Instrumentation?
In functional safety especially in industrial instrumentation, a fundamental idea is the Safety Integrity Level (SIL). SIL stands for the relative degree of risk lowering a safety feature offers. It is basically a performance criterion for a Safety Instrumented Function (SIF) meant to reduce possible risks.
IEC 61508 defines SIL as the whole safety function, considering hardware, software, and the process it guards rather than as a quality of any one component or device. Approaching all phases of the system life design, operation, maintenance, and decommissioning the standard presents a risk-based method to ascertain the SIL level of a SIF.
SIL 1 to SIL 4 comprises four SIL levels; SIL 4 denotes the maximum degree of risk lowering and safety performance. The likelihood of failing on demand (PFD) for the safety system decreases with increasing SIL.
Compliance with SIL criteria guarantees that safety systems operate consistently when required in sectors including chemical processing or oil and gas. Particular to gas detection, the EN 50402 standard defines standards for the functional safety of fixed gas detection systems, therefore augmenting IEC 61508.
Given growing focus on safety compliance particularly under European rules like ATEX the capacity of a safety system to carry out its intended purpose under demanding circumstances is very vital. Designing strong and compliant safety instrumentated systems therefore depends on knowing and using the right SIL level.
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