Has the SIL assessment been conducted for the device you are working on or that falls under your responsibility?
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With the rollout of Document No. 116, companies have entered a busy period carrying out SIL assessments for their installations. Sinopec’s goal is to complete 50% of these assessments by 2018 and another 50% by 2019. In reality, many companies fail to meet this timeline requirement. Recently, during my company’s monthly reporting tasks, I heard an SIL assessment specialist from a research institute affiliated with a state-owned enterprise say that for chemical processing units, there are 1 or 2 SIFs with a SIL rating of 2; generally, they have a SIL rating of 1 or no such rating at all. Process packages designed abroad usually do not include any components with a SIL rating of 2. Therefore, when conducting SIL assessments, these specialists try to ensure that there are as few SIF circuits with a SIL rating of 2 as possible. If it occurs, measures will be taken to avoid it (you know what I mean). I feel that it’s utterly ridiculous to draw such conclusions without seeing any information about the device; we’re all adults after all. To say such things in a meeting like this, and the leader still believes it. Conduct a survey now: Has the SIL assessment been carried out for the equipment you are working with or under whose supervision? What is the name of the device? How many are there of SIL3 SIFs, and what is their proportion of the total number of SIFs (which, in layman’s terms for plant personnel, refer to interlock circuits)? How many are there of SIL2 SIFs, and what is their proportion of the total number of SIFs? How many are there of SIL1 SIFs, and what is their proportion of the total number of SIFs? How many are there of the SIF grades without an SIL, and what percentage do they account for of the total number of SIFs? Response format: Unit name: 2 million tons/year diesel hydrogenation unit ； SIL2: 11, 26% of the total SIFs ； SIL1: 22, 52% of the total SIFs ； SILa(0): 9, 22% of the total SIFs ；
For safety instrumented systems, relevant regulations require that new projects must include a design for such systems, with the SIL level of the project being determined. This applies starting from 2018. The old project should complete the determination of its SIL level by the end of 2018. For the project our company has just completed, during the safety review in February, experts suggested that a SIS system design was necessary. As there was no other option, HAZOP and LOPA analyses were carried out, with considerations mainly based on the SIL1 level. The risks calculated were compared against the company’s guidelines, and since those guidelines involve a significant amount of subjectivity, the SIL level can be adjusted; nonetheless, SIL1 was generally adopted as the standard. However, when purchasing the instruments specifically later on, they will all be acquired as SIL2-grade instruments. The evaluation of the old devices has not yet begun. Once this new project is approved, we will then proceed with conducting an analysis of the entire plant. Regarding this classification issue, since we are a foreign-funded enterprise and the process package belongs to us, it involves confidential information, so we cannot disclose too much to external parties. So all the analysis is done by our company itself; all those analyses and scoring tasks have given me a huge headache. I’ve never received any systematic training before, and it feels like I’m just guessing my way through things. Fellow friends who are facing the same problems, please come and share your experiences with me.
I had never come across this concept before, so I found an explanation related to it; those who are not familiar with it can take a look at http://www.docin.com/p-1201495729.html
The name of the device cannot be disclosed, as the newly designed device involves two hazardous chemical processes. In accordance with relevant requirements, a HAZOP analysis was conducted by the design institute; meanwhile, consultations were carried out with safety advisory firms. Overall, it depends on the content of the process package and on the comprehensiveness and objectivity of the process engineers’ understanding of the associated risks, with the goal of obtaining as much information as possible regarding risk assessment. In the currently configured SIS system, there is at least: 1 for the entire SIL2 device ； The entire SIL1 unit has 11 ； There are 4 others that do not have SIL rating requirements (this is mainly due to cost and risk considerations; personally, I think the specifications are already quite high) ； Generally speaking, if a chemical plant reaches SIL2 level, it already indicates serious concern; SIL1 level is sufficient ； As for SIL3 level, it is generally more commonly used in power plants (nuclear power plants). This is closely related to costs; it is an assessment of overall benefits, and it is also greatly influenced by the PFD requirements set by the company.
At my classmate’s workplace, a new unit has been installed that uses foreign process packages; it’s a small unit, but it already has over 20 SIL2 elements. There is also a German process package; the unit is not large, yet SIL2 accounts for nearly 20% of the total SIF. For one of our oil refining units, a SIL assessment was conducted by a subsidiary of Sinopec; there are nearly 14 SIL2 levels, accounting for over 50% of the total SIF levels. This is the actual situation as I understand it.
This post was last edited by zhaotao555 on 2018-3-1 11:32. Well, in any case, the higher the level, the lower the relative probability of failure, which is better! This is also the first time in our factory that we have introduced the concept of SIL ratings. For those without a SIL rating, I’ve seen that the procurement process is similar to that for items with SIL rating requirements; it’s just that due to issues related to instrument selection and costs, sometimes it’s necessary to omit the SIL rating requirement. PS, the plant’s capacity is 2k–3k t/y.
I still don’t understand how SILA is defined exactly