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Standards for SIL certification and evaluation

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| 2020-06-22|Return

1. IEC 61508: Functional safety of electrical/electronic/programmable electronic safety related systems

(1) The IEC61508 standard specifies the basic safety requirements for both conventional system operation and fault prediction capability. These requirements cover general safety management systems, specific product designs, and process designs that meet safety requirements, with the goal of avoiding both systematic design failures and random hardware failures.

(2) The main objectives of the IEC61508 standard are:

Provide a systematic approach for safety supervision throughout the lifecycle of all components of safety related systems, including software and hardware; Provide methods for determining the safety functional requirements of safety related systems; Establish basic standards that can be directly applied to all industrial fields. At the same time, it can also guide standards in other fields, making the drafting of these standards consistent (such as basic concepts, technical terminology, requirements for specified safety functions, etc.); Encourage operators and maintenance departments to use computer-based technologies; Establish a standardized architecture and system with unified and coordinated concepts.


2. IEC61511: Functional safety requirements for safety instrumented systems in the process industry field

(1) IEC61511 is a functional safety standard specifically designed for safety instrumented systems in the process industry field. It is a professional standard launched by the International Electrotechnical Commission after the basic functional safety standard IEC61508. The coordinated standard for IEC61511 in China is GB/T 21109. In the process industry, instrument safety systems are used to perform instrument safety functions, and the IEC61511 standard addresses the issue of what level of safety integrity and performance instruments should achieve.

(2) For the confirmation of safety related device safety functions, SIL level is a widely recognized safety integrity definition method worldwide. For the process control industry, the relevant international standards mainly include the IEC 61508 standard (the fundamental basis for designing and operating safety instrumented systems). The IEC 61511 standard mainly focuses on systems used in process control applications, and is designed according to the IEC 61511 standard by device designers.


3. ISO13849-1: Safety of machinery - Safety parts related to control systems - Part 1: General principles for design

(1) The new version of ISO13849-1 standard will officially come into effect at the end of 2011, which will be a new milestone in the field of mechanical functional safety. In the past, some assessments of system failure probability have been added to the requirement for system determinacy, enabling a comprehensive safety assessment from components to the system. At the same time, this standard also provides designers with more quantifiable design implementation methods, such as adding parameters such as system safety level (PLr), system mean time between failures (MTTFd), system diagnostic detection range (DC), common cause fault prevention (CCF), etc., effectively solving the problem that the original EN954-1 standard cannot achieve quantitative judgment of system safety.

(2) The new version of ISO13849-1 standard provides more effective security assessment solutions for some new control methods. It can improve the safety level of increasingly complex mechanical equipment in control systems, ensure production safety and efficiency, and combine new technologies and design experience to help enterprises improve overall efficiency, productivity, and flexibility, ensure continuous production, reduce unexpected downtime, and reduce development, operation, and maintenance costs. Implementing this standard as soon as possible can ensure that mechanical manufacturers can seize the market advantage in fierce competition.


4. IEC62061: Mechanical safety - Functional safety of electrical, electronic, and programmable electronic control systems related to safety

(1) Both IEC/EN 62061 and EN ISO 13849-1:2008 standards include electrical control systems related to safety. After adopting these two standards, the same level of safety performance and safety integrity can be achieved. There are differences in the methods used for each standard, but they are all suitable for their respective readers. EN ISO 13849-1:2008 provides a limiting case in Table 1 of its explanatory section. When using complex programmable technologies, the highest PL performance level should be defined as PLd.

(2) In order to enable the adoption of complex security functions that can be executed by previously non-traditional system structures, the IEC/EN 62061 standard provides corresponding methods. In order to provide a more direct and simpler path required to perform more traditional security functions using traditional system structures, the EN ISO 13849-1:2008 standard also provides corresponding methods. The important difference between these two standards is that they are applicable to different technical fields. The IEC/EN 62061 standard is limited to the field of electrical systems. The EN ISO 13849-1:2008 standard applies to starting, hydraulic, mechanical, and electrical systems. The main defined parameters are PFH, MTTF, DC, SFF, etc.


5. IEC61326-3-2: Electrical equipment for measurement, control, and laboratory use - Requirements for electromagnetic compatibility (EMC): Safety related systems and for performing safety related functions (functional safety)

(1) The IEC 61326-3-1 and IEC 61326-3-2 standards have been published, which specify additional requirements for the immunity level of safety related equipment, including extremely low probability extreme situations that may occur in any location. Experimental simulation of harsh electromagnetic phenomena in the working state of equipment, such as instantaneous pulses being the transient state of analog digital circuits or digital signal transmission. In order to increase the reliability of the electromagnetic immunity of the Safety Integrity Level (SIL), more pulses should be applied or the test time should be extended compared to the basic standard during the electromagnetic phenomenon performance test, and the test level should be raised. For example, for equipment used for SIL3, the level of electrical fast transient test is 4kV, and the test duration should be 5 times the time specified in the basic standard.


6. ISO26262: Road Vehicle System Design Functional Safety

(1) The purpose of developing the ISO 26262 standard is to provide people with a better understanding of safety related functions and to explain them as clearly as possible. ISO 26262 is derived from the basic standard for functional safety of electronic, electrical, and programmable devices IEC61508. It is mainly positioned in specific electrical devices, electronic devices, programmable electronic devices, and other components specifically used in the automotive industry, aiming to improve the international standard for functional safety of automotive electronic and electrical products. Once this standard was proposed, it received high attention from major automobile manufacturers and auto parts suppliers, and actively promoted its implementation in product development.

(2) Based on the IEC 61508 standard, the ISO 26262 standard defines the safety of use for electrical and electronic systems. A major challenge in automotive design is how to pre evaluate potential hazards and risks, and adopt appropriate methods to reduce these risks. To facilitate this process, ISO stipulates that a "hazard and risk analysis" must be conducted at the beginning of development work.

(3) The automotive industry uses high-performance electronic devices for vehicle safety control. The ISO 26262 functional safety standard, jointly developed and recognized by major automotive manufacturers worldwide, specifies the requirements for the design of electronic components and software and hardware products for vehicles. With the promulgation and implementation of ISO 26262, it is possible to reduce the potential risks and hazards of accidents that may occur in vehicles in the future, thereby enhancing the adaptability and competitiveness of the domestic vehicle industry in the international market.


7. IEC61800-5-2: Standard for Adjustable Speed Electric Equipment - Part 5-2: Functional Safety Requirements

(1) IEC61800-5-2 defines the safety functions of integrated safety drives, which define a series of stop functions, namely: STO Safe Torque Off; Safety Stop 1/SS1/Safety Stop 2/SS2; Safety Operation Halt

(2) IEC61800-5-2 also defines some monitoring functions, including acceleration safety limits; Step safety restrictions; Safety restrictions on the direction of movement; Speed safety limit; Moment/force safety limit; Location security restrictions; Motor temperature safety limit.

(3) The IEC61800-5-2 standard mainly proposes functional safety requirements for safety encoders, safety decoders, AC servo systems, servo drives, servo motors, and other systems. For example, a motor controller that meets the requirements of functional safety technology will support safety functions such as Safety Torque Stop (STO) and Safety Stop 1 (SS1) to prevent accidental starting. The product design must comply with the requirements of EN 61800-5-2 standard. The IEC61800-5-2 standard has been transformed into a national standard, with the standard number GB/T 12668.5.2. The corresponding standardization committee in China is the Semiconductor Power Converter Technical Committee of the National Power Electronics Standardization Technical Committee for Speed Control Electrical Transmission Systems (TC60/SC1).


8. EN50156 IEC 61784-3: Digital data communication for measurement and control Part 3: Industrial network functional security regulations

This standard mainly defines the following content:

(1) Basic principles for implementing IEC 61508 safety related data communication requirements, including provisions for potential erroneous transmissions, response measures, and impact on data integrity

(2) Common content implemented by various technologies

(3) Independent description of functional security regulations for various communication industry clusters

(4) Several secure communication layers have been specified as part of the communication service regulations in the IEC61784-1 and IEC61158 system standards


9. EN50126 Railway Applications: Reliability, Availability, Maintainability, and Safety (RAMS) Specification and Description

This standard defines the RAMS (reliability, availability, maintainability, and safety) of a system, which includes reliability, availability, maintainability, and security. It also specifies the management and requirements for RAMS at each stage of the security lifecycle. As an important feature of system service quality measurement, RAMS is obtained through design concepts and technical methods at each stage of the entire system security lifecycle.


10. EN50128 Railway Applications: Software for Railway Control and Protection Systems

The software of railway control and protection systems has been classified into Safety Integrity Level (SIL), and corresponding standards have been formulated for different safety requirements. In the overall software development, evaluation, and testing process, including software requirement specifications, testing specifications, software structure, software design and development, software inspection and testing, software and hardware integration, software confirmation and evaluation, quality assurance, lifecycle Formulate corresponding standards and requirements for the initial development of procedures, such as documents.


11. EN50129 Railway Applications: Safety Related Electronic Systems

For safety management, the concept of safety lifecycle proposed in IEC61508 is introduced, which means that the safety part of safety related systems should be designed according to this step during the design process, and the entire safety assessment and verification should be carried out, with the aim of further reducing human errors related to safety and thereby reducing the risk of system failure.


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