Discussion on SIL level of field instruments
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A few days ago, I received a set of requirements for a process package from Germany. After reading them in detail, I found that the interlock circuit instruments were required to meet the SIL3 standard (for pressure transmitters). I contacted manufacturers such as ROSEMOUNT and SIEMENS, who replied that their instruments could achieve at most SIL2 level. Later, I discussed this with the German colleague, who explained that three SIL2 instruments combined in a 2OO3 configuration could be considered equivalent to SIL3. What are your thoughts? Are there any standards or regulations to support this? I hope experts can give some advice! ! !
This post was last edited by TUVFS on 2011-7-21 at 22:17 :lol This question was already answered a couple of days ago; the instrument level on-site is divided into hardware SIL levels and software SIL levels. The SIL level that we often talk about generally refers to the hardware SIL level. It’s probably because the SIL level of hardware is easier to quantify and test:) At present, for most foreign-brand safety instruments, the hardware level is usually SIL2, while the software level is SIL3. Instruments with a hardware safety level of SIL2 can achieve a SIL3 level through 1oo2 or 2oo3 redundancy, but a prerequisite for this is that the software must also have a SIL3 level; currently, abroad, the 2oo3 approach is widely used to achieve SIL3 in engineering applications. Firstly, it’s indeed safer; secondly, device manufacturers earn more for each additional unit sold :) (Just joking.) If you still don’t understand, feel free to contact me!
This post was last edited by TUVFS on 2011-7-21 at 22:18. In theory, the instrument can achieve a SIL3 hardware level, but it is difficult to design such an instrument, and the cost will be very high. Additionally, if we are tasked with carrying out the TUV certification, it might be slightly harder to obtain approval compared to SIL2. Previously, some domestic transmitter manufacturers approached us seeking certification for a hardware level of SIL3, but we advised them to go with SIL2 for now. But we do not rule out the possibility of other SIL3-rated transmitters emerging in the future; anything is possible in this world!
Thank you for the answer above~; I’ll ask you if there’s anything I don’t understand
1OO2 represents a 2-to-1 voting mechanism; in other words, whenever either of the two transmitters is activated, the signal is sent to the logic controller and ultimately to the actuator. 2oo3 is a 2-out-of-3 voting method: if any two of the three transmitters are triggered, the signal is sent out! Both 1oo2 and 2oo3 can achieve SIL3 level, but in the process industry, in addition to focusing on safety, availability must also be taken into account. By availability, it can be understood that production quality or efficiency should not be sacrificed just to consider safety. If the system stops operating accidentally due to a failure of the voltage transformer, although it becomes safer, it significantly affects normal production. With the 1oo2 voting method, if either of the two transmitters malfunctions, it can lead to an unintended shutdown, resulting in poor availability. With the 2oo3 voting method, since the probability of both transmitters malfunctioning simultaneously is very low (except in cases of common cause failure), its SIL level is the same as that of 1oo2; however, the reliability of this voting method is better than that of 1oo2, in other words, the probability of unintended shutdowns is lower. Therefore, since 2oo3 can balance safety and availability, it is easy to understand why, as mentioned by the original poster, foreigners recommend using the 2oo3 voting method to build a redundant structure for three SIL2 voltage transformers. Furthermore, regarding the question of whether a pressure transducer of SIL3 hardware level can be used to form a single-channel detection circuit, I personally believe that although the reliability of SIL3 level is better than that of SIL2, the failure rate is only extremely low, rather than zero. And once a single-loop SIL3-rated pressure transducer fails, it is very likely to cause an unintended shutdown; therefore, it is easy to understand why there are so few SIL3-rated transducers, and why no one uses them to create single-channel monitoring circuits!
Could the original poster explain in detail what STL levels are? I’m learning about it
Reply to 6# okaway: It depends on what aspects you would like to know; the topic of SIL levels covers a pretty wide range!
Reply: What does 2# TUVFS 1002 2003 mean? Learned* it
Reply to 9# Sports Car Ant Tribe: The original poster has already explained it clearly; why ask again?
Which companies are currently doing well in SIS systems? Who has a larger market share? I’d like to know!