SIL - Safety Integrity Level

Basics for SIL

Problem: For many years, increasingly complex microsystem technology in line with the state of the art has also been used in control systems with safety function. To ensure that this technology meets safety requirements, special standards for functional safety must be fulfilled. In addition to ISO/DIN EN 13849 and IEC/DIN EN 62061, the IEC/DIN EN 61508 is also used in the machine sector due to its broad international acceptance.

The IEC 61508 represents a special challenge in application, among other things due to the special approach of considering not only the individual components but also the safety function over the entire life cycle of a machine or a system. In this context, detailed documentation and the quantification of safety-related reliability are required. This often results in a need for advice, to those developing safety-related electronic products as well as to those using and operating them.

ENCOS applies the following rules and regulations:

• IEC 61508 Part 1 - 7 Functional safety of safety-related electrical/electronic/programmable electronic systems
• IEC 61511 Part 1 - 3 Functional safety - Safety systems for the process industry
• EN 50 129 Safety-relevant electronic systems for signal technology  

The steps can be described as follows:

The requirements are divided into individual stages. The stages represent a measure of the reliability of the system depending on the hazard. These serve to protect the health of employees, the environment and other goods. Safety functions are implemented by a safety circuit, which can consist of various equipment such as sensors, control elements and actuators.

Operators of systems with safety-related functions determine the safety integrity level in a risk assessment. To determine whether redundant structures exist and whether the safety function is to be considered continuously or upon request, its failure behavior is checked. A classification is made for the interconnection of the various equipment (sensors, actuators, control elements, etc.) and not for individual components.

Our services at a glance:

• Execution of SIL calculations
• Support in the preparation of the machine-related risk assessment
• Analysis and evaluation of plant functions and their potential hazards