“In petrochemical enterprises, in order to cooperate with the production process, it is necessary to transport and store raw materials, semi-finished products, and finished products. For this reason, enterprises have built a large number of various storage tanks. The production and management departments of the enterprise need to master the important data such as liquid level, temperature, volume and quality of the storage medium in the tank every day, not only to ensure the accuracy and timeliness of the data, but also to ensure the safety of the storage tank and prevent accidents. Accurate detection of storage tank parameters and effective management of process flow in tank farms are of great significance to the safe and smooth operation of related production units.
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In petrochemical enterprises, in order to cooperate with the production process, it is necessary to transport and store raw materials, semi-finished products, and finished products. For this reason, enterprises have built a large number of various storage tanks. The production and management departments of the enterprise need to master the important data such as liquid level, temperature, volume and quality of the storage medium in the tank every day, not only to ensure the accuracy and timeliness of the data, but also to ensure the safety of the storage tank and prevent accidents. Accurate detection of storage tank parameters and effective management of process flow in tank farms are of great significance to the safe and smooth operation of related production units.
Due to the specific national conditions of our country, the management of tank farms has been carried out manually for a long time, and there is no “monitoring system” in the true sense. Taking oil tanks as an example, at first, experienced workers used oil dipsticks to monitor the oil tanks by measuring the liquid level of each oil tank (the so-called “manual gauge”). This method is primitive and cumbersome, with great influence of human factors and low precision, and the toxic and harmful gases in the dangerous area cause great harm to the operator’s body, and it is very unsafe for the operator to climb up and down on the oil tank. In order to improve the accuracy of the parameter measurement of the storage tank, protect the health of the workers, and reduce the labor intensity of the workers, in the early 1990s, each oil tank was basically equipped with instruments that can automatically measure the liquid level. The instrument generally consists of a primary instrument and a secondary instrument. The primary instrument at the site collects the liquid level parameters of each oil tank and sends it to the secondary instrument in the centralized control room through a unified analog signal such as a 4-20mA DC current signal or a special communication protocol. At this time, the operator can sit in the control room and look at the status of each oil tank through the secondary instrument. However, these secondary instruments can only “monitor” the parameters of the storage tank and cannot implement control, so the specific control work still needs to be carried out manually. With the continuous expansion of the production scale, the scale of the tank farm is also increasing, and the types of oil products are also increasing. The management method that managers monitor and control the tank farm in accordance with the production plan formulated by the production department and the accumulated experience over the years shows more and more deficiencies in real-time, accuracy and rationality. At the same time, due to the continuous improvement of the automation level of oil refining units, higher requirements are also placed on the management of tank farms, so the responsibility and pressure of managers are also increasing, which is very detrimental to the safety of production.
With the continuous development of computer technology, the continuous improvement of reliability, and the substantial reduction of prices, the application of computers in the industry has become more and more popular. Programmable logic controller (PLC) and distributed control system DCS (Distributed Control System), which is composed of multiple computers hierarchically, are widely used in all walks of life. Due to the wide application of DCS in various units of the refinery, the majority of engineers and technicians have rich experience, so they refer to the practice of DCS in each unit when constructing the monitoring system of the tank farm. In terms of hardware structure, similar to the oil refining unit, the instruments on the tank farm convert parameters such as temperature and liquid level into unified analog signals and send them to the operation control part of the control room point-to-point. However, since the tank farm is different from the general oil refining unit, the outstanding feature is that the geographical distribution is very wide and the control is scattered. Therefore, when the system structure adopts the same point-to-point connection method as the oil refining unit, it needs to use much more cables and wiring than the general unit. Terminals and bridges and other accessories require a lot of manpower during system construction, and it is difficult to ensure the reliability of the connection. Numerous connection points and difficulties in fault diagnosis also bring great inconvenience to future system inspection and maintenance. And the long-distance transmission of the signal greatly reduces the accuracy of the signal.
The field bus technology in the world has gradually developed and matured, and it has shown its own influence and advantages in some specific application fields. Fieldbus is a standard, open, two-way multi-station digital communication system used between process control field instruments and control rooms. The two-way, all-digital signals are realized between instruments and control systems through the bus in a one-to-many manner. Communication, reducing a lot of wiring, easy system installation and maintenance, at the same time, the control tasks are delegated to local instruments, the danger is completely dispersed, the autonomous ability of the system is strengthened, and it can respond to field changes in real time. In my country, the development of fieldbus technology has just started, especially in the management of tank farms. How to combine the characteristics of fieldbus technology itself and my country’s national conditions, apply it to various industries, and promote the modernization process of my country’s automation field, This is the main problem faced by the majority of scientific and technological personnel. The production process of the petrochemical industry is complex and changeable, and the production environment has potential explosion hazards. In this field, the following four basic requirements are put forward for the new control system based on fieldbus:
1) There must be complete explosion-proof protection measures to ensure the absolute safety of the production process in the explosion-hazardous environment.
2), to have high reliability to ensure the reliable transmission of data under any circumstances. That is to do “line redundancy”.
3) Corresponding to the feature of “continuous process”, the control system must have the ability to process analog data. And also to meet the “online parameterization” requirements.
4) All field devices can be plugged and unplugged online without affecting the normal operation of the system.
NCS3000 networked control system is a complete automatic control system based on FF fieldbus technology independently developed by my country, with the characteristics of full digitization, intelligence, networking and openness. NCS3000 adopts digital signal, FF HSE high-speed bus and FF H1 bus complement each other to form the network platform of enterprise integrated automation system. It has strong performance and has the ability of remote debugging and self-diagnosis of equipment. At the same time, it can integrate various popular industrial automation equipment and monitoring configuration software. It is a truly open networked control system.
Since the 1970s and 1980s, safety barriers have been widely used to make the control system meet the explosion-proof requirements, and this method has been used until now. However, the use of safety barriers makes the structure of the control system complicated and increases the difficulty of construction. Since the mid-1990s, major explosion-proof manufacturers in the world have developed products that integrate the safety barrier and the I/O module of the controller, thereby simplifying the structure of the system. Some remote I/O products with explosion-proof function have come out one after another. In order to match as many control systems as possible, the products manufactured by these manufacturers all use the popular field bus as the medium for communication with the controller. And in order to take advantage of remote I/O in hazardous areas, new remote I/O products can be directly installed in hazardous areas by taking a series of explosion-proof measures. With the rapid development of IT technology and network technology, the requirements for the control system are getting higher and higher, from pure precise control to security control and monitoring management. Therefore, the field bus system based on serial communication technology has been widely used in the field of control because it has the functions of distributed control and data transmission.
Because the NCS3000 networked control system adopts the field bus, the control system structure will be simple, the system installation cost will be reduced and the maintenance will be easy; the user can freely choose the field equipment of different manufacturers and brands to achieve the best system integration and a series of advantages, the field bus Technology is getting more and more attention. The NCS3000 networked control system launched by Shenyang Institute of Automation, Chinese Academy of Sciences has the characteristics of full digitization, intelligence, networking and openness. It takes fieldbus technology as the core and OPC technology as the link. Industrial automation equipment such as I/O, DCS and PLC are organically integrated, with high degree of automation and control accuracy, and have been successfully applied in the tank farm management industry, providing a complete set of solutions for the enterprise’s comprehensive automation system, and achieved good effect. Figure 1 shows a typical remote I/O product.
Figure 1 Typical remote I/O structure
As can be seen from Figure 1, the remote I/O system consists of a motherboard, a power supply module, a gateway module that supports different bus protocols, various I/Os that process digital input and output, analog input and output, and temperature input signals. composed of modules. The working principle of the system is as follows: All kinds of instruments in the field are connected point-to-point with the I/O interface of the remote I/O through wires and cables. Inside the motherboard) to the gateway, and then the gateway transmits the signal to the field bus on the upper layer through the bus interface on the motherboard, and finally reaches the control system (DCS/PLC) through the bus. The signals from the control system are transmitted via the opposite path. The power supply of the entire remote I/O is provided by the power supply module connected on the system motherboard, and the power supply of the power supply module is supplied by the external 24V DC power through the increased safety wiring terminal.
The remote I/O has the following outstanding features: (1) It can be directly applied to hazardous area 1, which can save a lot of cables; (2) It communicates through the field bus, and the system is easy to expand. Moreover, the power supply, gateway, and internal/external bus are all redundant, which ensures the high security of the system; (3) All modules can be plugged and unplugged online, which greatly facilitates the construction and maintenance of the system; (4) There is no need for safety barriers and DCS The I/O module of /PLC can save a lot of cables and accessories, which greatly reduces the initial investment of the system; (5) Powerful diagnosis and self-diagnosis functions and efficient digital communication greatly improve the advanced nature of the system; (6) It can be connected to traditional field equipment without changing the traditional installation and connection method and supports the transmission of HART protocol, which paves the way for the transformation and expansion of the existing system.
It can be seen from the above characteristics that when the remote I/O is used to form a system, it not only brings into play many advantages of the field bus, but also overcomes the problems faced by the field bus when it is applied in the dangerous area.
With the continuous development of my country’s economy, the demand for petroleum products in all walks of life is also increasing substantially. Therefore, in order to rapidly improve the refining capacity and better meet these requirements, my country has established a large number of oil refining enterprises in various places in recent years, and the original oil refining enterprises are also continuously improving their own refining capacity. In order to make production efficient and safe, oil refining enterprises have put forward higher requirements for the automation management level of various oil refining units and public works such as tank farms. However, the survey of major domestic oil refineries shows that the automation management level of each tank farm is generally very low, and for a long time, there has been a situation where emphasis has been placed on the continuous improvement of the control automation level of oil refinery units and despised the improvement of the automation level of the tank farm monitoring system. , The accident rate of “roofing” and explosion of oil tank is obviously higher than that of each device. In recent years, especially when the “DCS” transformation of each device has been basically completed in the past one or two years, the voices and requirements for improving the automation level of the monitoring system of each tank farm are also getting higher and higher. To this end, the two major domestic companies “Sinopec” and “PetroChina”, which are mainly engaged in oil refining production, are preparing to spend a lot of special funds to transform and upgrade the monitoring systems of the tank farms in each oil refinery. However, there are many problems mentioned above when DCS is used as the monitoring system of the tank farm, and many difficulties are encountered when applying fieldbus in foreign countries to solve these problems. Therefore, how to design a set of advanced, efficient, fully functional and economical monitoring system suitable for tank farms is a problem that engineers and technicians at home and abroad need to solve urgently.
The successful solution of this problem will definitely improve the automation management level of the tank farm and then the management level of the entire factory, reduce the labor intensity of workers, improve the working conditions of workers, avoid accidents, and reduce the initial investment in system transformation and future operation. The cost and so on are very important.
The new tank farm monitoring system has the following advantages:
1. The application of hierarchical control and multiple redundancy technology makes the system more efficient and safer.
2. The software and hardware of the system adopt today’s advanced mainstream products, and users will not have to worry about the future transformation, upgrading and secondary development.
3. Friendly man-machine interface, simple and intuitive operation.
4. The perfect application of field bus technology, remote I/O technology and safety barrier technology makes the future expansion of the system very convenient.
5. The I/O interface unit can be directly placed in the danger zone 1, thereby saving a lot of cables and related materials such as terminals, slot boxes, and bridge frames.
6. The saving of a lot of hardware materials makes the construction very simple, thus saving a lot of labor costs.
7. The reduction of the number of wiring points is bound to greatly reduce the number of fault points, thereby significantly reducing the maintenance cost of the system.
8. A variety of diagnosis and self-diagnosis functions make the fault diagnosis and positioning of the system very fast.
9. The I/O layer and the field layer support “on-line plugging and unplugging”, and there is no need to stop the system during maintenance and replacement of defective parts, which greatly improves the ability of the system to run continuously.
10. Multi-level safety management measures and detailed operation record function make the management of the system more scientific and effective.
NCS3000 networked control system is a commercialized, industrial-grade product component system hardware platform with good performance-price ratio, which ensures the reliability and ease of operation of the system, and the system scale is also easy to expand. It consists of a database server and several management computers. The real-time data from each control system (the first-level field refueling automatic control system of the automatic control system in the oil storage area) is stored in the database service in real time through the gateway of each control system. To ensure the accuracy and integrity of the data, the database server provides query, statistics and analysis functions for these data, and can generate various reports for management and analysis. In addition, through the use of dedicated confidential lines, the data of each oil depot and station can be automatically transmitted to the central service at the oil plant on a regular basis, so that the management personnel of the oil plant can directly and clearly understand the various data of each oil depot and station. To truly realize that “high-tech enhances the comprehensive assurance capability of the troops”. Due to the use of advanced fieldbus technology, OPC technology, information integration technology and distributed technology, the demand for cables and terminals and the workload of post-maintenance of field devices are greatly reduced, and the integrity of the collected signals is guaranteed. The accuracy of the signal makes the original mutually isolated various information resources organically integrated into the central database, thus forming a comprehensive automation system in the entire reservoir area, achieving good social and economic benefits, and being well received by users.
The Links: 2DI30Z-100 LC260W01-A5K4