Functional Safety according to IEC 61508/62061: Practical Guide for Maintenance Equipment

Introduction

Functional safety in industrial environments is not an option, but a critical technical need defined by the probability of failure on demand. International standards IEC 61508 and IEC 62061 establish the reference framework for designing, implementing and maintaining security-related control systems. In practice, the objective is to guarantee that, in the event of a failure in the control system, the machine goes to a safe state, minimizing the risk for operators. For maintenance teams, the correct application of these standards is essential to prevent accidents and guarantee operational continuity.

Scope and Applicability

The IEC 61508 standard, titled 'Functional safety of safety-related electrical/electronic/programmable electronic systems', acts as the base (top-level) standard. For its part, the IEC 62061 standard, 'Machinery safety - Functional safety of electrical, electronic and programmable control systems related to safety', is a sector standard that applies the principles of the IEC 61508 specifically to the field of industrial machinery. They are applicable to any plant that uses automated systems, from automotive assembly lines to complex chemical processes, where a failure of the control system can result in personal or environmental risks.

Table: Comparison and Requirements of Security Standards

Impact on MRO Operations

Implementing functional safety dramatically transforms Maintenance, Repair and Operations (MRO) operations. Maintenance is no longer just about repairing failures; involves maintaining the integrity of the certified Security Integrity Level (SIL). Any modification or replacement of components must be documented and validated. Component substitutions for non-certified equivalents are not permitted, even if they fit mechanically. Traceability of installed components is mandatory, and any changes to security system hardware or firmware require full risk re-validation.

Component Requirements

Safety components, such as safety relays, inductive safety sensors, light barriers, safety PLCs and actuators, must have CE marking and specific SIL certification. UNITEC-D supplies components that rigorously comply with these requirements, ensuring traceability from the original manufacturer. Installing components without specific certification will invalidate the SIL of the machine, which is a critical vulnerability to any technical audit or accident.

Compliance Checklist

1. Verify that the safety components have the CE mark and the corresponding SIL certification.
2. Check that the installation manuals are available, updated and in the local language.
3. Record all functional tests in the equipment maintenance book.
4. Ensure that safety cables are separated from power cables to avoid electromagnetic interference (according to IEC 60204-1).
5. Carry out periodic calibrations of the safety sensors according to the maintenance plan.
6. Validate that the emergency stop buttons function correctly under load conditions.
7. Maintain a detailed historical failure log (MTBF) of safety components.
8. Confirm that no bridges, bypasses or temporary overrides have been made in the safety circuits.
9. Verify the physical integrity of optical barriers and mechanical protectors.
10. Perform documented testing of security system response time.
11. Ensure that personnel handling safety components are trained and certified in functional safety.
12. Check that the firmware versions of the safety PLCs are compatible and up to date.
13. Validate safety distances from moving elements according to ISO 13855.
14. Review safety signage and danger labels on components and panels.
15. Conduct annual internal audits of all security control systems.
16. Document any changes or replacement of components with your product code and certificate.
17. Verify the resistance of the installed components to environmental conditions (temperature, vibration, humidity).
18. Confirm the full traceability of the safety components installed in the plant.
19. Perform system stress tests after any major maintenance.
20. Ensure that the Lockout Tagout (LOTO) procedure is correct and implemented.

Common Noncompliance Issues

Auditors frequently encounter bypassing safety sensors to avoid machine downtime ('so production doesn't stop'), the use of standard replacement components instead of safety-certified ones, and the lack of updated documentation following changes to the PLC configuration. These acts reduce the SIL of the system immediately, leaving the installation out of standard.

Penalties and Liability

Non-compliance is not a mere administrative irregularity. In the event of an accident, the consequences are serious: immediate stoppage of production by the labor authority, fines that can reach a significant percentage of the annual turnover (depending on local legislation such as the Occupational Risk Prevention Law in Spain or equivalent in LATAM), increase in insurance premiums or denial of coverage, and personal civil and criminal liability for those responsible for maintenance and safety who authorized or allowed the operation of unsafe systems.

Conclusion

Functional safety is an integral component of operational excellence and risk management. Maintaining the required SIL levels requires diligence, certified components and rigorous documentation processes. To ensure continuity and safety in your plant, trust only components with guaranteed certification. Visit our UNITEC-D E-Catalog to access a complete range of certified components for security control systems.

References

• IEC 61508-1:2010, Functional safety of safety-related electrical/electronic/programmable electronic systems - Part 1: General requirements.
• IEC 62061:2021, Machine Safety - Functional safety of electrical, electronic and programmable control systems related to safety.
• EN ISO 13849-1:2015, Safety of machines - Safety-related parts of control systems - Part 1: General principles for design.
• EN ISO 13855:2010, Machine safety - Positioning of protective devices depending on the approach speeds of parts of the human body.