SIL certification requirements for intelligent transmitter products

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Before we get started, let’s take a look at a set of numerical codes: CWEME-11KQ-0210720-1040zbzx0170HAZB-2010091503-90635-1103N1062011-034-2-020. Surely some of you will ask, what do these codes mean? I guess those who work in technology research and development don’t often come across such things, but those who work in marketing like me can tell at a glance that these are the numbers of procurement or bidding projects. What do these numbers represent? Let’s continue: CWEME-11KQ-021 – Tender for the coal-to-gas project in Keqi, Inner Mongolia, operated by Datang International. Products required: float level switches, intelligent transmitters. Required SIL rating: SIL3. Reference number: 0720-1040zbzx0170. Sichuan Petrochemical’s butyl octanol production facility is also issuing a tender; product required: float level gauge. Required SIL rating: SIL2. Reference number: HAZB-2010091503-9. Shanxi Lu’an High-Purity Silicon Technology Co., Ltd. is issuing a tender; products required: pressure transmitters, differential pressure transmitters, temperature transmitters. Required SIL rating: SIL2. Reference number: 0635-1103N106. Henan Kaixiang Fine Chemicals Co., Ltd. is conducting a tender for the second phase of its BDO production project; product required: temperature transmitter. Required SIL rating: SIL2. Reference number: 2011-034-2-020. Shaanxi Yanchang Petroleum (Group) Co., Ltd. is developing an integrated energy and chemical industry park in Jingbian; products required: split-type temperature transmitters, integrated temperature transmitters, dual-redundant temperature transmitters. Required SIL rating: SIL2. …………………………………………………………………………………………………………………………… Those who have doubts about these preliminary results can check online to find out exactly what SIL ratings are required for intelligent transmitters (such as pressure transmitters, temperature transmitters, level transmitters, etc.) used in industrial processes, as specified in the actual tender documents! Why are SIL rating requirements necessary for intelligent transmitter products? Before discussing this issue, let’s first review what the definition of Safety Integrity Level (SIL) is. The SIL level is a metric for assessing the safety integrity of the functions in E/E/PE safety-related systems; it is used to determine the safety integrity requirements for the safety functions assigned to such systems. The overall SIL level consists of the hardware’s SIL level and the system’s safety integrity. The safety integrity levels for functional safety are divided into 4 different levels: the lowest level is SIL1, and the highest level is SIL4. In the petrochemical industry, the commonly seen SIL levels are SIL2 and SIL3. For verifying the safety functions of safety-related devices, SIL is a globally recognized method. For the process control industry, the main relevant international standards are IEC 61508 (the basis for designing and operating safety instrumented systems). IEC 61511 focuses on systems used in process control applications; device designers follow IEC 61511 standards while carrying out their designs in accordance with IEC 61508 standards. In the IEC 61508 standard, in addition to introducing the concept of SIL levels and classification methods, it also specifies basic safety requirements regarding both normal system operation and fault prediction capabilities. These requirements cover general safety management systems, specific product design, and process design that meets safety requirements, with the aim of avoiding both systematic design flaws and random hardware failures. From this brief overview, it is clear that specifying the SIL level of equipment during the procurement of field instruments can effectively reduce the likelihood of failures in the safety control system, which are caused by the malfunctioning of hardware or software security functions within the instruments. This approach helps to ensure greater safety throughout the production process. Surely some people will say: Our field transmitters have undergone relevant certifications, such as CE certification, as well as ATEX explosion-proof certification and so on. However, it is important to keep in mind that for transmitter devices, the EU CE certification primarily evaluates aspects such as the electrical safety of the device itself (electrical clearance, creepage distance, etc.), explosion protection capabilities (ATEX), and EMC electromagnetic compatibility. However, given the operational characteristics of process industries, even if it is possible to ensure that the equipment does not act as a ignition source in potentially explosive environments, for transmitter products the primary safety function is detection; it is necessary to guarantee the accurate output of the (4-20) mA analog current signal. If the detection function fails and the (4-20) mA signal becomes abnormal, it will inevitably prevent the pressure, temperature, and other values from the reaction vessel from being transmitted correctly to the safety instrument system. In such cases, an accident is almost inevitable. Moreover, if the transmitter lacks safety features such as redundancy and voting mechanisms, a failure of the entire system due to a malfunction in the equipment can lead to even more serious production accidents. Why do field devices such as intelligent transmitters or actuators also need to meet SIL rating requirements, in addition to the Safety Instrumented System (SIS)? This is what we commonly refer to as the \"weak link effect.\" In process safety control systems such as those in the petrochemical industry, all components within a given circuit must meet safety integrity requirements; otherwise, the safety of the entire circuit will be determined by its weakest link. For the safety of automatic control systems, regardless of the SIL level of the core SIS or ESD, if the peripheral devices such as those in the detection circuit and actuation circuit do not possess appropriate safety functions—such as transmitters that lack any redundancy or voting mechanisms and other safety enhancements—the safety integrity of the entire control circuit cannot be ensured. What is the SIL rating for typical intelligent transmitter products? Based on the current situation both abroad and in China, most transmitter products possess SIL2 certification, while only a few have SIL3 certification. Regarding the well-known Rosemount 3051S series of transmitters, their hardware safety level is SIL2, while their software safety level is SIL3. If you need specific certification details, feel free to contact me. Furthermore, for example, the SIL level certification for most of E+H’s smart transmitters is carried out by our organization, TUV SUD. The products certified by us, such as pressure transmitters, can also achieve a SIL3 level in terms of their software’s SIL rating. Specific products include: Cerabar S: PMP71, PMP72, PMP75, PMC71; Deltabar S: PMD70, PMD75, FMD76, FMD77, FMD78; Deltapilot S: FMB70. At that time, there were many other smart transmitter products that were certified by us; due to space constraints, those who wish to discuss this in more detail can contact me! If field instruments such as smart transmitter products are to undergo SIL level certification, what evaluations and tests need to be considered? In addition to considering conventional electrical safety and EMC electromagnetic compatibility aspects, SIL certification also evaluates parameters such as the PFD, HFT, SFF, and SIL level of the hardware. It furthermore conducts comprehensive verification of the overall development process, hardware structure, software architecture, etc. Only transmitters that have been assessed using functional safety system methods can help improve the overall safety performance in the field. In fact, it is not difficult for smart transmitters to pass the SIL2/SIL3 certification; the main issue is that R&D personnel in domestic companies are not very familiar with the specific procedures involved. You are most welcome to contact me at any time to discuss issues related to the SIL rating of field devices. Thank you!