1. Introduction
In modern industrial conditions, the safety of equipment is determined not only by physical enclosures, but also by integrated control systems that minimize risks for personnel. The safety level of such systems is measured according to international standards, such as IEC 61508 and ISO 13849. SIL (Safety Integrity Level) is a key indicator that determines the system's ability to perform a safety function in the event of a dangerous situation. Understanding SIL is imperative for maintenance engineers, as the use of non-compliant components can lead to system failures and serious incidents.
2. Scope of application
Safety standards such as IEC 62061 (SIL-based machine safety) and ISO 13849-1 (PL performance level) apply to all automated manufacturing processes where a failure of the control system could lead to injury. This covers metalworking, chemical industry, food processing and packaging. Compliance with the standards is mandatory for equipment manufacturers, integrators and end-users who carry out modernization or major repairs (retrofitting).
3. Key requirements and SIL levels
The SIL level defines the probability of dangerous failure per hour (PFH). The higher the level, the lower the chance of failure.
| SIL | Mean probability of dangerous failure (PFH) | Risk level |
|---|---|---|
| SIL 1 | 10^-6 to 10^-5 | Low |
| SIL 2 | 10^-7 to 10^-6 | Average |
| SIL 3 | 10^-8 to 10^-7 | Tall |
| SIL 4 | 10^-9 to 10^-8 | Critical |
Proof tests are determined by the component manufacturer and must be strictly adhered to.
4. Impact on MRO operations
Implementing SIL requires a change in procurement and maintenance approaches. Components for safety systems must have appropriate documentation (Safety Manual, Declaration of Conformity). Replacing a safety component with a standard counterpart without SIL certification is a direct violation of the standard. Each change in the security chain requires updating the documentation on the calculation of system reliability.
5. Requirements for components
Not all components require SIL certification. However, the elements included in the "functional safety chain" (sensors, logic controllers, actuators) must be certified. This includes safety valves, light barriers, emergency stop buttons and PLC safety modules.
6. Compliance checklist
- Check for CE marking and compliance IEC 61508/62061.
- Obtain a SIL certificate from the manufacturer for a specific product.
- Check the service life (Mission Time) of the component.
- Make sure that the SIL level of the component corresponds to the calculated SIL of the system.
- Document the installation date of each certified component.
- Establish a schedule of mandatory checks (proof tests).
- Exclude the use of components that do not have the manufacturer's documentation.
- Ensure correct connection according to safety scheme.
- Check the response time of the system (Response Time).
- Validate the system after replacing any component.
- Ensure availability of safety instructions for personnel.
- Keep the test reports during the entire period of operation.
- Use only original spare parts from certified suppliers.
- Provide protection against unauthorized access to security settings.
- Train personnel on emergency stop procedures.
- Perform a physical check of the integrity of fences and sensors.
- Document the test results in the safety register.
7. Common inconsistency problems
Auditors often find the following violations: use of standard relays instead of safe ones; ignoring the terms of scheduled inspections (proof tests); inconsistency of the calculated SIL level with the real configuration of the equipment; lack of certification documentation for spare parts purchased through unauthorized channels.
8. Penalties and liability
In Ukraine, violations of labor protection rules that led to accidents due to malfunctioning safety systems entail administrative and criminal liability for managers and responsible engineers. In addition, insurance companies refuse to pay out when it is established that non-certified components are used in critical safety circuits.
9. Conclusion
Selecting certified safety components is a critical aspect of maintenance. This is not only a requirement of the standard, but also the basis of stable and safe operation of an industrial enterprise. To ensure uninterrupted and compliant operation of your equipment, consult the UNITEC-D E-Catalog, where you will find a wide selection of certified components for your automation systems.
10. List of references
- IEC 61508:2010 - Functional safety of electrical/electronic/programmable electronic safety systems.
- ISO 13849-1:2023 - Machine safety. Parts of control systems related to security.
- IEC 62061:2021 - Machine safety. Functional safety of control systems.
- DSTU EN ISO 13849-1:2016 - Machine safety. Parts of control systems related to security.
