When it comes to machinery safety, ensuring the reliability of the safety functions is critical to preventing accidents and injuries. One way to do this is by understanding and implementing safety integrity levels (SILs). But what are SILs and how are they used in machinery safety standards?


Let’s explore!

What are Safety Integrity Levels?



Safety integrity levels, or SILs, are used to specify the required reliability of safety functions in machinery applications. The SILs are divided into four levels, SIL1, SIL2, SIL3, and SIL4, with SIL4 being the highest level of reliability and SIL1 being the lowest.

The ISO and IEC Standards



The ISO and IEC standards are two of the most widely recognized machinery safety standards that address SILs. The ISO standard, ISO 13849-1, Safety of machinery – Safety-related parts of control systems – Part 1: General principles for design, specifies the SILs for safety-related control systems. The IEC standard, IEC 61508, Functional safety of electrical/electronic/programmable electronic safety-related systems, provides guidelines for the design and implementation of safety functions in electrical, electronic, and programmable electronic systems.

SIL Requirements



The requirements for each SIL vary depending on the standard being used. In the ISO standard, the requirements for each SIL are based on the probability of a failure of the safety function, the severity of the consequences of the failure, and the level of independence of the safety function. The requirements for each SIL in the IEC standard are based on the likelihood and severity of the hazards associated with the machinery, the reliability of the controls used to mitigate the hazards, and the level of protection provided to the workers.

Determining the Appropriate SIL



To determine the appropriate SIL for a specific application, you should consider the likelihood and severity of the hazards associated with the machinery, as well as the level of protection required for the workers. You should also consider the specific requirements of the relevant machinery safety standards and the intended use of the machinery.

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