What are the differences and advantages/disadvantages between fieldbus control and the installation of conventional field instruments?

Bus control facilitates data transmission through communication protocols; it is essentially like a small internet, with each smart meter functioning as a computer. When communication issues arise, the field control system and the various meters will still operate normally and will not stop working due to wiring faults. At present, the use of bus meters is still restricted by many factors, among which high cost is the main one........

Buses have communication protocols that are used to convert signals into a unified format; they also involve coordination of communications regarding who acts first and who acts later. The bandwidth of the transmitted signals determines the amount of data that can be transmitted, as well as the speed of transmission. Bus control emerged to accommodate the advent of smart meters; it is not just about the signal content, as many smart meters are able to reflect their own status. This status information is also part of the data; just imagine how convenient it is to have control over the conditions of the instruments from the center console. The development of instrument technology aims at enhancing safety and efficiency, as well as reducing costs

1. Although fieldbuses reduce the need for cables and labor costs, the individual instruments using these buses are relatively expensive, and they tend to be tied to a specific brand; changing to another brand is difficult, and spare parts as well as maintenance costs are high. 2. The maturity of bus technology presents issues, as large-scale use carries high risks; when many devices are connected to one bus, any problem that occurs will affect all the devices on that bus. 3. Returning to the issue of saving money, due to the intrinsic safety requirements, an intrinsic safety bus allows only a limited number of instruments to be connected to it; generally, no more than 8 instruments can be connected to such a bus ； For flameproof buses, although more instruments can be connected to them, the total length of the bus is limited due to signal attenuation issues; it generally should not exceed 1200 meters. Even if the total length is within limits, there is still a restriction on the number of instruments, which is usually no more than 16, as a precaution. 4. Conventional instruments such as pressure and differential pressure transmitters all have a bus system, but not all instruments have field bus capabilities; in such cases, an AI-to-bus converter or a bus-to-AI converter is required, which incurs additional costs. 5. When choosing a bus, it is best to use instruments from the same manufacturer for all of them. At present, Emerson seems to offer the widest range of options; other manufacturers present more difficulties. However, if you want to use one manufacturer’s transmitters and another manufacturer’s valve positioners, etc., problems will indeed arise. Although the openness of bus technology is advocated by everyone, and there is coordination through bus foundations, the degree of interoperability remains limited. 6. Bus cables have high requirements; parameters such as resistance, inductance, and capacitance must meet strict standards. Currently, no manufacturers in China are able to meet these requirements. The field bus used in the Sike project encountered many problems at that time. The last issue was related to the ordinary dual-cable system used for power transmission; various different products were tried, but none worked. Eventually, cables imported from Germany, presumably of the LEON brand, were used, and only then did the system start to function properly. This is the most significant negative example in this regard. 7. Interlocking cannot use a bus; it must be point-to-point. In summary, we must acknowledge the advancement of bus technology, but its maturity is questionable. In short, use it with caution; use it in situations where it’s not essential, on a limited scale, and think carefully before using it. Do not use it on a large scale unless it becomes as mature as DCS first.

Fieldbus control and conventional field instruments

Agree with the view from the 4th floor; the use of buses seems to have cooled down a bit in recent years.

Fieldbuses have advantages, but they are not yet ready to fully replace DCS. Main reason. First, it’s expensive; the one-time cost is relatively high at present ； Secondly, it is immature; in particular, there are no unified standards. Mobile phones can support dual SIM dual standby, but this is not possible with buses ； Thirdly, safety standards have risen; to meet the SIL3 certification requirements, each bus must have its own dedicated connection, which prevents the utilization of the original advantages. 　

The maintenance cost for individual instruments is high, but it remains relatively stable. It depends largely on the quality of the field instruments you purchase; diagnosing problems can be tricky as well. When installing them, it’s essential to pay attention to shielding and grounding, as most problems are caused by poor shielding connections

I learned it, ::(:(:(:(:(:(:(

In fact, fieldbus technology is now quite mature. Although there has been ongoing controversy in China, and fewer projects related to it are being carried out these days – mainly because such technologies are no longer promoted in large enterprises like SEI – the widespread use of fieldbuses in China’s petrochemical industry is now a thing of the past. However, they have seen extensive application abroad in recent years. Personally, I believe that replacing DCS with fieldbuses is a misconception; currently, fieldbuses are used both domestically and internationally as part of DCS, and there has never been anything called an FCS system. Fieldbus instruments and traditional instruments are both used in conjunction with each other. The advantage of fieldbuses lies mainly in the amount of information they can transmit; a fieldbus system can be considered as a form of the Internet of Things. Saving on cables and installation costs is just part of it; unfortunately, most users in the country fail to take advantage of the benefits that such systems offer in terms of information transmission, with many users not even having AMS or FDM systems at all.

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