Safety standard ISO 13849 detailed explanation

ISO 13849 is the basis for assessing the safety of complex machine control systems. It is a basic functional safety standard that contains internationally harmonized requirements relating to the determination of the required performance level and the determination of safety-related control components until the implementation of the safety function.

Designed to help build a mechanical safety system with sufficient reliability. For machine manufacturers and users, ISO 13849 is a guide for safe operation.

Although the categories used to define the structure of the system are the same, this safety standard replaces the old EN 954-1 standard with many improvements. In order to operate the machine safely, some of the basic contents of ISO 13849 need to be understood.

Traceability to ISO 13849

ISO13849 dates back to the old standard EN 954-1, and the IEC 61508 FAQ has a good concise history of ISO13849-1.

Figure 1- A snapshot of the IEC 13849 FAQ for ISO 61508

EN 954-1 is an application-level standard for building systems using components such as laser scanners, safety relays and sensors. A typical machine safety function is to check whether a door or guard is open or closed, and to stop the machine when it is open. For security, EN 954-1 mainly depends on the architecture of the system, and for higher security levels, a two-channel architecture is required.

However, EN951-1 has the following problems:

- Mainly used in electrical. Hydraulic pressure. Pneumatic and mechanical control systems that do not cover complex E/E/PE systems;

- Failure to focus on the complexity of security features;

- Qualitative evaluation of the system, without the requirement of the probability of system failure;

- The classification of safety levels is not clear, and the relationship between risks is not clear;

- Does not take into account the variability of external factors of the control system.

ISO 13849, the successor to EN 954-1, refers to the level of safety as PL (performance level). The PL of the implementation depends on a combination of reliability (MTTE), diagnostic coverage (DC), and class (architecture).

Significant changes to ISO 13849

In 2023, the International Organization for Standardization (ISO) publishes a new version of ISO 13849-1. The revision provides a set of guidelines, such as for determining performance levels, to provide better support for implementation.

Compared to the previous ISO 13849-1:2015, ISO 13849-1:2015 has made some changes:

- The overall structure is clearer, with a focus on implementing security functions as a combination of multiple subsystems;

- Improve and extend the safety function specification;

- Improvement and description of the software;

- Determine the required performance level; Change of parameter P;

- Extended functional safety management guidelines;

- Supplementary information on safety requirements specifications;

......

The new version of ISO 13849-1 covers the functional safety of the following safety-related devices:

Safety sensor, safety light curtain, safety carpet, safety PLC, two-hand control system, safety controller, safety door switch, safety encoder, safety relay, industrial robot, etc.

ISO 13849 is a specification lamp and tool for the safe operation of machinery

The topic of "safety" is a cliche, and a safe environment can protect workers and equipment when operating machinery. Therefore, ISO 13849, as a safety standard for verification, can be used to control the basic health and requirements of system safety-related components.

ISO 13849 consists of two parts, developed and published by ISO (International Organization for Standardization) :

Part 1: General Principles of Design - This part of EN IOS 13849 provides guidance for those involved in the design and evaluation of control systems.

Part 2: Verification (BS EN ISO 13849-2:2012) - This part of EN ISO 13849 specifies the verification process for safety functions, categories and performance levels of safety-related components of control systems.

ISO 13849 is suitable for what

ISO 13849:2015 provides safety requirements and guidance on principles for the design and integration of safety-related components (SRP/CS) of control systems, including software design. For these parts of SRP/CS, it specifies features that include the level of performance required to perform the safety function. It is suitable for high-demand and continuous mode SRP/CS, regardless of the technical type and energy source of the machinery used (electrical, hydraulic, pneumatic, mechanical).

Basically, IOS 13849 uses statistical analysis to determine the frequency of failures and hazards of components and circuits over time to find performance levels (PL). The PL can then be used for risk assessment to ensure that appropriate safety devices are implemented.

But the complexity of ISO 13849 has increased over the years, and Xiaobian wondered how easy it would be to apply it outside of the experts. One area that is still relatively simple is the proposed risk map for risk assessment, where the required PL has been determined.

*注：通过风险图里的参数S, F ,P 来确定此安全功能需要的性能等级PLr。

The assessment criteria include the severity of the injury, the frequency of exposure to the risk, and the likelihood of avoiding the risk.

Why is ISO 13849 important

ISO 13849 is important because designing safety features in machinery is one of the best ways to ensure the service life of equipment. This is a positive measure to maintain a safe working environment.

Both manufacturers and integrators have a significant responsibility when it comes to operational safety. Protecting workers, machines and the bottom line in a safe environment is a worthwhile investment for anyone in the industrial sector.

Safety has never been more important in today's factory environment, and the robotics industry has an extraordinary safety record, but robots still present unique hazards to heating. As industrial robots expand globally, safety standards help keep workplaces safe.

Conclusion

1, ISO13849 inherited from EN954, focusing on the analysis of the structure of safety-related components, the realization of PL depends on reliability (MTTE), plus diagnostic coverage DC, mean risk time (MTTFD), common cause failure (CCF) and other parameters to assess whether the corresponding performance level (PL) is reached.

2. ISO13849 defines the use of performance levels (PL) to evaluate a complete safety system or safety-related component. The performance level indicates the security function that a security system can achieve under foreseeable conditions. The performance level can be divided into five levels from low to high: PLa, PLb, PLc, PLd, PLe.

3. ISO13849 defines the relationship between PL and SIL. It should be noted that a PL level can be claimed to have reached the corresponding SIL level, but the reverse is not the case.

4, ISO13849 does not limit the use of technology, electronic/electrical, hydraulic, pneumatic, mechanical, etc. can be applied. It can be seen that in the mechanical field, because the way to achieve is not limited to electronics/electricity, but also involves hydraulic, pneumatic, etc., ISO13849 has a wider range of applications.