Is Siemens’ PCS7 system a DCS?

PCS7 is a mess; anyone who uses it suffers as a result. 1. The protection of users’ investments is poor. You want to upgrade the software, and they tell you that your hardware isn’t suitable; the hardware also needs to be upgraded, but my hardware has only been in use for a few years. 2. The configuration is cumbersome. PCS7 is a freak combination of a PLC S7-400 and a bunch of software. With true DCS systems, many functions don’t require user intervention, whereas PCS7’s numerous configuration options can be overwhelming, making it difficult for those who aren’t computer science graduates to handle them easily. 3. Honeywell and Foxboro, as well as Yokogawa, are probably several times better than him. 4. An air separation unit equipped with PCS7 uses three or four sets of controllers, whereas the Honeywell TPS uses only one set. It’s obvious to everyone who is stronger; there’s no need to claim that its analog processing speed exceeds that of DCS, when in fact the load on its controllers is very low.

I forgot to mention that the main market for PCS7 is in China; it hardly sells abroad, especially in developed countries (except in Germany). People there aren’t fools – Chinese consumers are easy to trick by Germans, especially those who have an excessive admiration for the S brand.

I understand that the difference between DCS and PLC lies merely in their initial design approaches: PLCs focus more on processing digital signals, while DCS focuses more on processing analog signals.

This post was last edited by qiaopeng1231 on 2009-12-3 20:01. My approach might differ from everyone else’s; I have always believed that the distinction between PLCs and DCS should not lie in whether there are more digital signals or analog signals. I firmly believe that only a system designed specifically for process optimization can be called a DCS. Or call it an excellent DCS. For general industries, there is no special optimization; if the system has a high degree of integration, it is called DCS. If the system is separated, with the lower-level programming handled by the PLC manufacturer’s software and the upper-level control handled by independent monitoring software, then calling it PLC is more appropriate. On this basis, let’s discuss PCS7. It is an evolution of the S7 PLC system, and that is something no one can deny. However, DCS systems are originally divided into those with a PLC-based architecture, those with a PC-based architecture, and those with a traditional I&C-based architecture. --This classification was proposed by me during lectures at one of the top three foreign companies in the automation industry; it is a standard that differs from those used by university professors. Traditional systems such as Foxboro, Yokogawa, Honeywell’s older systems, and Emerson DeltaV all originated from the concept of instrument control systems, with an emphasis on analog circuit control. It is also what people refer to as the “true DCS”. --It was DCS in the past, it is still DCS now, and it will remain DCS in the future. Its software style has always revolved around instrument systems, in line with industry conventions. So the system is simple and efficient to use. The style is fresh, and the systems are generally not large-scale, though there are very few exceptions. Domestic companies such as Xinhua, Huawen, and Hollyland, as well as foreign companies like Metso, use industrial-grade PC architectures for their hardware; many of them employ control kernels based on WIndCE or QNX. The system architecture has typical PC characteristics. For example, Xinhua runs its own developed control engine on the WinCE embedded environment in industrial-grade PCs. Huawen runs its own control engine in the Linux environment of industrial-grade PCs ； HollySys deploys the controller engine from German Codesys on the QNX environment of industrial-grade PCs. --Codesys is regarded as the world’s largest and most advanced manufacturer of SoftPLC control engine systems (system platforms) ； Similarly, some of the systems at Guodian Zhishen run Infoteam’s control engine on industrial PCs. Metso’s system resembles an industrial PC more, from its appearance to its core. The architecture used is not the issue; the key question is what you can solve for users and in what technological environment it can be applied. . . What about those DCSs with a PLC-based architecture? PCS7 isn’t the earliest, but it’s undoubtedly the most successful. Actually, the first one was Honeywell. Back in the PlantScape era, and even before that, HW tried to use PLC-based hardware systems on non-mainstream DCS systems. The PlantScape system uses AB’s ProcessLogix PLC hardware platform; it’s just referred to as a DCS. It represents the most standard, typical PLC platform, and was developed a few years before Siemens’ PCS7. . . After PlantScape was upgraded to E-PKS, all versions up to R210 continued to use the Ab PLC hardware platform. Similar systems include GE’s PPS and Proficy Process System, which are also based on GE’s own PAC RX3i and 7i PLC hardware platforms. ----Currently, as industry experts often say, PLCs and DCS systems are beginning to merge, and it’s becoming difficult to distinguish between them. This is mainly because many traditional PLC manufacturers, such as Siemens, GE, and AB, have introduced DCS systems, which are essentially based on their own PLC hardware platforms. Many traditional DCS manufacturers, such as ABB, sell the AC800M as a PLC after splitting it apart ； Companies like Honeywell have directly introduced PLC systems such as Masterlogic. So, returning to the topic of PCS7: first and foremost, regardless of the architecture, it remains a DCS. As the wise Deng Xiaoping said, no matter what kind of cat it is, if it can catch mice, then it’s a good cat. I still emphasize that the biggest difference between DCS and PLC lies in whether they are optimized for specific industrial processes. For example, it is generally believed that Honeywell and Yokogawa are excellent DCS systems, typical representatives of such systems. However, in metallurgical applications, their performance lags far behind that of PLCs. This shows the difference between DCS and PLCs. But then why do DCS systems like Siemens’ PCS7 and ABB’s 800XA perform so well in the metallurgical industry? Conversely, PCS7 and 800XA, which perform excellently in metallurgical applications, are not at all popular in petrochemical systems. . . PCS7 is a generic platform with obvious signs of being put together piecemeal; yet, as a platform, it possesses the advantages that come with such a structure. Systems developed on this standard platform can achieve excellent results if optimized for specific industries. 1. The brewing and beer industry – this has been mentioned many times – the BarauMat system based on the PCS7 architecture holds over 70% of the global market share. Is it because Siemens’ S7 PLC has better hardware than Yokogawa’s CS3000? This is because Siemens works closely with numerous manufacturers in the brewing industry and those involved in beer production processes, to develop many industry-specific process modules that are easy to use. The screen operations are user-friendly, and its features are well suited to the needs of the brewing industry. Everyone agrees that the most professional system in the brewing industry is Siemens’ BarauMat system – it is a standard, typical DCS to which no one dares to challenge, and no one considers it a PLC! . But if this brewery builds a new pump room and uses an S7 PLC, even if it’s an S7-400, and even if it still uses Siemens’ WinCC for monitoring, and it doesn’t use the specialized DCS system for the brewing industry called BrauMat, people will still consider it a PLC. 2. Thermal power industry. The Siemens PG Group uses the S7-400 PLC from Siemens Automation Group as its DCS, along with T3000. Strictly speaking, however, T3000 is no longer an upgraded version of PCS7, as its core architecture has changed. But no one thinks that the T3000 system uses an S7 PLC – it’s just a PLC. . . T3000 ranks fourth in terms of performance among million-unit DCS systems worldwide, and second in terms of performance for turbine DEH systems ； In terms of domestic performance for DCS systems in units with a capacity of one million units, thirdly, the performance of turbine DEH systems is currently first ； The T3000 is an industry DCS system fully optimized for the thermal power industry. Furthermore, in industries such as gas power generation and IGCC, T3000 is also the second-best system in the world, second only to GE. 3. Water treatment industry. The Siemens PCS7 system remains the best-performing in the world -- see ARC’s market research report. In the Americas, the water treatment industry does not recognize Siemens, and PCS7 is not very well regarded in the Middle East either. However, in Europe, Africa, Asia – especially in China – the water treatment industry highly values Siemens, which in turn has led to excellent performance for PCS7. The SiWater system, developed on the basis of PCS7, is a specialized PCS7 system designed for the water treatment industry. It’s still the same principle: it’s not about how good Siemens’ PLCs are; what matters most is whether you’re truly willing to invest more time and effort in a particular industry, and to make optimizations specific to that industry. Returning to that question, in the water treatment industry, for projects requiring DCS systems, SiWater is more practical than most DCS systems. What does it matter whether you call the Siwater system a PLC or a DCS? 4. In the glass industry. The Siglass system, developed based on PCS7, remains unparalleled. It’s not really because the S7 PLC is that powerful; rather, it’s due to Siemens’ close cooperation with numerous manufacturers in the glass industry. As a result, significant optimizations, improvements, and upgrades were made to its PCS7 system specifically for use in this industry. 5. In the metallurgical industry, interestingly, when it comes to the most expensive and complicated wiring methods, Siemens and ABB hold over 70% of the global market share. It’s not because of the outstanding performance of PCS7. It’s because Siemens and ABB’s rolling mills are very powerful. Then, control systems need to be integrated in line with the manufacturing process; they should be optimized and adapted fully for that process system. If they can work well with external manufacturers involved in the production process, there’s no reason why they can’t work well with one’s own processing equipment. . . This industry. Nor does anyone consider PCS7 to be a PLC. All acknowledge that it is a DCS. And it is generally recognized that it is better than Honeywell and GE. Emerson has a much better DCS. There’s no need to give more examples. I think my approach should at least represent an objective standard, one that is recognized by ARC and F&R as well. --Although the IEC does not specify this, PLCs and DCSs are distinguished based on whether they are optimized for a particular industry. . . Furthermore, if PCS7 is equipped with a relatively powerful processor, its processing speed is indeed faster than that of HW and Yokogawa’s, by a significant margin. It includes not only digital signals but also analog signals. . . For example, PCS7 can achieve fast closed-loop control within 5 ms, while companies like Yokogawa simply cannot do better than 50 ms. . . 50ms is definitely enough for the chemical industry, but what about metallurgy? In some process sections, it’s over 10ms – there aren’t even doors!

This post was last edited by jacob451 on 2009-12-3 12:52. PCS7 indeed has its strengths in advanced calculations. Such as arrays, third-order matrix multiplication. Advanced operations are often used in algorithm control or advanced control. This is something that FOXBORO and Yokogawa cannot match. Array operations seem to be feasible only with MOORE’s APACS at the moment (UOP uses array operations to control the lock hoppers). Unfortunately, MOORE was also acquired by Siemens. As for hardware, he’s indeed a freak; one can look down on it. However, PCS7 uses S7-400, whose central chassis is independent, which can be considered hardware redundancy. You can see that what’s called CPU redundancy in DCS these days simply means installing two CPUs in a central chassis; if that central chassis is damaged, having CPU redundancy is of no use. So PCS7 brings a new concept to everyone in this regard. So don’t be too critical; the Chinese can see from PCS7 that the Germans know how to save money (PCS7 can be built using S7-400 controllers and S7-300 I/O), and it also introduced a new concept of DCS safety (with an independent central chassis). The above are merely my humble opinions; please feel free to correct me.

5# qiaopeng1231, the analysis on the 5th floor is really insightful!

In fact, PCS7 also has a dedicated DCS version for cement, called CEMAT. At the same time, the PCS7 version for the pharmaceutical industry is about to be released. From what I’ve seen, the main improvements and enhancements involve the batch component, the end-to-end quality monitoring component, the QTS interface, as well as GMP and FDA compliance features. Except that Batch is process-related, the rest are almost all of a “purely software” nature and are only relevant to this industry. For example, can you use Yokogawa’s CS3000 for pharmaceutical manufacturing? It can definitely be done. Is there full-process quality tracking, something similar to the function of MES? I don’t remember. I don’t remember there being any components certified by FDA and GMR either. No, in that case you have to add these software modules from external sources; so there is likely no good integrated solution available.

There is a saying that when the controller and monitoring systems share a single database, it is called DCS; whereas if the databases for the controller and monitoring systems are relatively independent, it is referred to as PLC

Who can tell me what the biggest drawback of PLCs is? In the chemical industry

5# qiaopeng1231 Could you please provide a detailed and systematic overview of the differences between Siemens PCS7 and HW, as well as Yokogawa, in the chemical industry? What are their respective advantages and disadvantages? ? ?