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What is the failure rate of SIL certification?
During the SIL certification process, a concept we often mention is the equipment failure rate, which is a core term in SIL certification. One could say that without determining the failure rate, the SIL certification is incomplete and not comprehensive. So, what exactly is the concept of failure rate?
Firstly, to understand failure rate, we need to grasp what "failure" means. According to GB/T 20438.4 and also the definition in IEC 61508, failure is "the termination of the ability of a functional unit to perform a required function, or the operation of the functional unit in a non-required manner." A more intuitive way to understand this is: normally, y=f(x), but after failure, it becomes y≠f(x), where f() represents the pre-set function, and y stands for our safety expectations. This also explains why "function" is the same word for both "function" and "function" in English.
This statement might be too formal and not easily understood by the general public. So, speaking in more colloquial terms, let's liken it to a lighting system. When a lighting system doesn't light up or doesn't do so according to our set requirements, it's considered to be faulty.
So said, you might all know that when a product does not function as per our specified requirements, we can say it is defective. Then, what is the probability of this defect occurring? That's the failure rate.
After understanding what failure is, we can start to categorize the types of failure. In the concept of functional safety, failures can be divided into two main categories based on their generation causes: systematic failure and random hardware failure. Among them, random hardware failure is quantifiable. The calculation process of PFDavg is based on a probabilistic analysis of random hardware failure.
In the SIL certification, we analyze the theoretical product model and market sales data to determine the product's failure rate, thereby combining with other parts of the SIL certification to form a comprehensive system, ensuring the reliable execution of safety functions.

What are the two main aspects that SIL certification primarily evaluates?
The product itself, as well as the conformity of the hardware and software functions of the intended certified product, to the requirements of IEC61508 or more specific industry functional safety standards, such as hardware failure rates and failure modes.
Another key focus of our examination is the quality management system employed during the development process, the qualifications of the R&D personnel, and the organizational structure, ensuring that the methods used and the document system adhered to throughout the product development process meet relevant standards.
Through these two aspects of examination, we can say that from the entire company to the R&D process and finally to the specific certified products, a complete closed loop has been formed, ensuring the reliable and safe realization of the product's safety functions.

SIL 2 and SIL 3 certifications are two different levels. According to international certification standards, the SIL 3 level is higher than the SIL 2 level. Specifically, this is reflected as:
An actuator of SIL1 rating should have a failure probability controlled at ≥10^-6 to <10^-5 per hour of continuous operation.
SIL2 is from ≥10^-7 to <10^-6. SIL3 is from ≥10^-8 to <10^-7.
Of course, the requirements for SIL3 level are much higher than those for SIL2.
Most products currently meet the requirements with SIL2 or SIL3 certification levels.

As the awareness of industrial accidents and their impact on society grows, more and more companies recognize the importance of safety.
In modern process industry production, due to the complexity of processes and the multitude of equipment, any failure can have serious consequences for employees, the public, equipment, or the environment.
The SIL certification process is about helping companies fully leverage their good engineering practices and safety technologies (IEC61508 and IEC61511) to prevent industrial accidents from recurring. This is because these experiences and technologies are based on a wealth of actual experience and lessons learned.
With the issuance of the IEC 61508 and IEC 61511 series standards, a systematic functional safety assessment and testing process can effectively address this issue.
SIL certification is a third-party evaluation, validation, and certification process based on standards such as IEC 61508 (GB/T 20438), IEC 61511 (GB/T 21109), IEC 61513, IEC 13849-1, IEC 62061, IEC 61800-5-2, etc., to assess and confirm the Safety Integrity Level (SIL) or Performance Level (PL) of safety equipment. Functional safety certification primarily involves assessments of document management (FSM) for the development process of safety equipment, hardware reliability calculations and evaluations, software assessments, environmental testing, and EMC electromagnetic compatibility testing. SIL certification is divided into four levels: SIL1, SIL2, SIL3, and SIL4, encompassing both product and system levels, with SIL4 having the highest requirements.