Functional safety begins with a well-founded risk analysis.
Electronic systems, especially in safety-related applications such as railway technology, must function reliably even in the event of a fault. The use of quantifiable parameters is crucial here. The Safety Integrity Level (SIL) plays a central role, describing the required safety integrity level of a safety-related system and thus forming an essential component of functional safety.
What is the Safety Integrity Level (SIL)?
SIL (Safety Integrity Level) is an internationally recognised classification for assessing the functional safety of safety functions. Safety integrity is the degree of confidence in a safety function. The higher the safety integrity, the higher the confidence in the safety function. Safety integrity encompasses safety against random errors and systematic errors. In railway technology, the SIL is defined by the standard IEC 61508 and for railway system in the standards EN 50126, EN 50129 and EN 50716. Depending on the risk and potential impact of a safety function failure, a SIL between Basic Integrity, 1 and 4 is assigned. SIL 4 represents the highest safety level.
Basic Integrity is often used to classify software/hardware not involved in a safety-related application (e.g. PIS, CCTV, HVAC)
SIL 1
SIL 1 represents the lowest safety level. SIL 1 is applied to safety functions where a failure could cause minor injury or limited damage (e.g. basic automated protective functions)
SIL 2
SIL 2 represents moderate safety integrity. SIL 2 is applied to safety functions where a failure could cause significant injury or major equipment damage (e.g. medium-risk railway subsystems.)
SIL 3
SIL 3 represents high safety integrity. SIL3 is applied to safety functions that protect against severe hazards with potential for serious injury or fatality (e.g. train control systems)
SIL 4
SIL 4 represents highest safety integrity. SIL 4 is applied to safety functions whose failure could lead to catastrophic consequences such as multiple fatalities or very high system damage (e.g. railway signalling)
Our service: SIL derivation in accordance with standards
Enotrac supports you in determining the SIL in accordance with the procedures set out in standards EN 50126, EN 50129 and EN 50716. Our experts derive the required SIL based on a structured risk analysis.
The following points are taken into account:
System functions and their safety-related aspects
The functions of the system are analysed in detail to identify components whose failure could have safety-critical consequences. Both the technical architecture and the functional processes are considered in order to identify potential hazards at an early stage.
Probability of occurrence and extent of damage
In the risk analysis, we assess how likely a fault or failure is and what impact it could have on people, infrastructure and operations. This assessment forms the basis for classifying the required SIL and helps to define the safety requirements in a targeted manner.
Requirements for availability, reliability and fault behaviour
Depending on the area of application, systems must be robust to faults to varying degrees. We check how reliably a system functions under normal and fault conditions, how it reacts to faults and how quickly it can recover from them. These characteristics are directly incorporated into the SIL derivation and ensure that the system meets the required safety level.
Are you planning a safety-related system?
We accompany you from risk analysis to standard-compliant SIL determination. Contact us, and together we will create systematic safety.
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