1, PLC feeding system is mainly characterized by: reliable operation, fast running speed; building block structure, flexible combination; good compatibility; programming and generation of simple, rich; network function. PLC system can well complete the industrial real-time sequential control, conditional control, counting control, stepping control and other functions; able to complete the analog/digital (A/D), digital/analog (D/A) conversion, data processing, communication networking, real-time monitoring and other functions.

2, DCS has the following main features; full-featured; network communication technology; complete open system; high reliability; comprehensive and professional; the realization of human-machine dialogue technology; flexible system expansion; strong management capabilities.

3、FCS mainly has the following characteristics: highly decentralized structure of fully automatic batching system; strong interoperability; validity and integrity of data; controllability; high security; flexible expansion.

As the fieldbus FCS automated batching system is still in the development stage, the standard has not been unified, the equipment manufacturers are in a wait-and-see state, the existing bus standard intelligent equipment prices are obviously high (such as 20,000 yuan for the transmitter). Iron and steel industry has fewer regulatory circuits, monitoring parameters, the characteristics of the fieldbus FCS speed dosage system application is less, some applications are also used as a remote terminal of the PLC system, generally using Profibus bus. Here mainly introduces DCS and PLC atmospheric pressure batching equipment selection.

PLC and DCS in the process of seizing the market, the two draw on each other, penetration, integration, greatly increasing the user's selectivity in the design and use. At the same time, due to a variety of vertical dosage system production manufacturers, product replacement fast, but also to the system selection brings some difficulties. Now based on the different characteristics of PLC systems and DCS, in the industrial automation construction and transformation projects, the metering and dosage system design selection and application of the following principles of selection summarized.

1, according to the spiral batching control scale and complexity

Different automation production process, isobaric dosage control scale and complexity is different, usually in the positive pressure dosage of larger scale, higher degree of complexity of the DCS is preferred, because the system is based on the characteristics of the development of the vacuum dosage, it is a large number of analog data information can be better processed, analyzed, calculated to complete a variety of complex, cumbersome regulation and control of calculations, and therefore be able to complete the scale of the large, High complexity of the negative pressure batching work.

2, according to the scale of investment and project economic efficiency reasonable choice

In some small and medium-sized automation projects, especially small and medium-sized transformation projects, less investment, smaller instrumentation and control system should be given priority to choose the price is relatively low modest, cost-effective PLC system. Such as in 1991, JISCO a steel 3 # slab continuous casting machine two cold water renovation project and plate plant heating furnace renovation project and other projects in the design, according to this principle in the spiral dosage system selected TI-545 series PLC system, but also achieved very good results.

3, consider system continuity, compatibility and communication performance

In some automation projects, such as the original project has a computerized dosage system, it is necessary to consider the continuity and compatibility of the system. If the transmission dosage system occupies a large proportion, it is necessary to consider the connection with the production management computer system information network that communication performance. 2005, the first set of computerized dosage system - MODICON584 series PLC in the JISCO ironworks 4 # blast furnace charging system application was successful in the future of the ironworks blast furnace renovation or construction, due to the consideration of the MODICON production PLC products have strong compatibility and communication performance, the use of MODICON series PLC products (first 584 series, and later more advanced 984 series and Quantum series) on the blast furnace system control or upgrade the system, to ensure that the system's advancement, continuity, compatibility, and to facilitate the information of the blast furnace system between the communication links and ironmaking production management network. Communication links and iron production management network construction, reducing the control software configuration repeat tedious labor, reducing the inventory cost of spare parts.

4, considering the technical services of explosion-proof system manufacturers

Currently in China's PLC systems and DCS sales market, foreign manufacturers have a large share of major foreign manufacturers in China generally high energy product promotion and technical service organizations, and foreign companies often reorganization, merger or consolidation, due to the product structure of the company, sales strategy, market share of a different direction, merger or consolidation, in the Chinese market, technical promotion and service, there will be some Therefore, when we choose the system, we should fully grasp the information and consider the technical service of the system manufacturer, so as to protect the advancement and development of the chosen system, and to ensure the supply of sufficient technical support and spare parts.

To sum up, the principle of speed batching system selection can be considered from the following aspects: system size, complex program, the system's inexpensive capacity and communication performance, as well as the manufacturer's technical support and after-sales service. In the automated production of weighing automatic dosage system, according to the process of object complexity of different, as well as for the quantitative automatic dosage of the reliability of the reasonable choice of different automatic dosage, to ensure the production of dosage automation level, reduce the cost of the project has a very important significance.