Design of oil depot monitoring system based on Siemens PROFIBUS and AS-i bus technology

“As a link for coordinating crude oil production and processing, refined oil transportation and supply, oil depots play an important role, and their performance and efficiency will directly affect the overall benefits of oil companies.However, in my country, the level of automation of oil depots is still far from the level of attention paid to oil energy. For example, there are few automation equipment, and the production management process still relies on manual monitoring and operations, with large personnel and low efficiency; low degree of automation, equipment functions Single, the application of intelligent instruments is not enough, the integration between systems is difficult, and the data is scattered; the use of traditional signal transmission methods increases the amount of installation and laying of traditional instruments and pipelines.

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1 Introduction

As a link for coordinating crude oil production and processing, refined oil transportation and supply, oil depots play an important role, and their performance and efficiency will directly affect the overall benefits of oil companies. However, in my country, the level of automation of oil depots is far from the level of attention paid to petroleum energy. For example, there are few automation equipment, and the production management process still relies on manual monitoring and operations, with large personnel and low efficiency; the degree of automation is low, and the equipment functions Single, the application of intelligent instruments is not enough, the integration between systems is difficult, and the data is scattered; the use of traditional signal transmission methods increases the amount of installation and laying of traditional instruments and pipelines, and increases the difficulty of on-site maintenance and explosion-proof.

Oil depots are generally located in relatively open areas, occupying a large area, and the tank farms are scattered, far apart, and far away from the main control room. In the monitoring of oil depots, it is necessary to control the oil pump valve position on the field layer to effectively control the oil in and out. ; There are strict restrictions on storage tank temperature, oil mist density, tank wall pressure, etc., and TV monitoring is carried out on the site to ensure the safety of the work site. Due to the dispersion of the working environment and the serious consequences of on-site emergencies, it is not allowed to have too long maintenance time lag, which restricts manual real-time maintenance, and also produces the “centralized management, decentralized control, and timely maintenance reporting that we need.” ” control system functional requirements. When transferring oil, it is mainly necessary to detect the valve position status and oil flow of the oil depot. During the storage period, parameters such as oil level, temperature, density, pressure, etc. are collected, and a series of physical parameters measured in the tank area are controlled. It is displayed on the industrial computer in the laboratory, supplemented by a network structure with smooth information flow, to form a unified MIS system to facilitate the management of the oil depot.

Facing the increasingly fierce competition in the international energy market, under the background of frequent safety accidents in petrochemical enterprises, it is urgent to improve the efficiency of oil depots, speed up the turnover, strengthen safety management, improve the level of automation, and build a unified oil depot by technical means of informatization and automation. The data collection and processing platform will ultimately optimize the overall functions of petroleum enterprises and enhance their comprehensive competitiveness.

2. Overview of oil depot monitoring system engineering

2.1 Introduction of oil depot

The oil depot is the base for receiving, unloading, storing and supplying oil products, and crude oil has the properties of being explosive, flammable, volatile, and easy to accumulate static electricity, so the storage area is large and the route is far, which leads to the monitoring station being far away from the site of each tank farm. At the operation level, it is necessary to transmit the information on site to the monitoring station in a timely and effective manner, so that the master station can quickly give instructions. In general, according to the architecture of the factory automation system, the entire oil depot can be divided into three different levels, namely the bottom operation layer, the monitoring layer and the management layer. The operation layer includes on-site monitoring equipment, automatic detection, and automatic control systems. The specific implementation includes the operation process of metering, receiving and dispatching oil products, automatic detection and control of oil tanks, on-site video security of oil depots, and oil and gas alarm equipment. In the network environment, the monitoring layer collects the data and information collected by the operation part, provides a unified monitoring platform for the system, meets the requirements of centralized management, provides data for the top management system, and supports daily business management and decision-making. The structure of the oil depot management system is shown in Figure 1.

Design of oil depot monitoring system based on Siemens PROFIBUS and ASCi bus technology

The oil depot described in this paper has a total of 6 × 1000m3 storage tanks, which are hundreds of meters away from each other. For each tank area, there are automatic oil delivery systems, tank area oil storage metering systems, oil and gas leakage monitoring and alarm devices, video monitoring, spray cooling Equipment, on-site instrumentation is more complex.

2.2 Tank farm testing equipment and control objects

As mentioned above, each of the 6 tank farms has a tank level detection device, a temperature measurement device, a magnetostrictive level gauge is used to measure the liquid level, and a thermal resistance is used as a temperature sensing probe; in order to avoid excessive temperature To deteriorate the oil quality of the oil in the oil tank and ensure that the oil mist density is within the intrinsically safe range, the temperature is required to be controlled below 35 °C. Area automatic measurement unit; in the process of unloading and conveying oil, the mass flowmeter is used to accurately measure the quality of oil. parameter. The digital solenoid valve is used to control the sending and receiving of oil, and it is equipped with an oil spill prevention switch to achieve quantitative reduction to reduce oil and gas losses. A degassing filter is installed in front of the meter to ensure the measurement accuracy, and an IC card reader is also equipped on site for self-service oil distribution by the user. These constitute the unloading and conveying unit; in the aspect of safety protection and alarm, lightning protection and anti-static grounding switches are used. Set up safety detection devices, and add combustible gas alarm devices and high-resistance oil leakage detection devices at suspected combustible gas leakage points such as tank farms, pump rooms, and valve rooms to eliminate hidden dangers. In addition, there are several cameras with different angles in the tank area for dynamic monitoring. Multiple video images can be connected to the switcher and monitor through coaxial cables, so that the main control room can fully grasp the dynamic information of the on-site images of each tank area. Fire-fighting measures respond quickly, and these constitute security monitoring and over-limit alarm units. The above are some of the detection systems and actuators on site, all of which are more advanced products and have corresponding protection levels according to the installation environment requirements.

3. Development plan of oil depot monitoring system

3.1 Fieldbus

Fieldbus is a new communication standard for industrial control systems arising from the extension of digital communication networks to industrial process sites. It has the following advantages: (1) Digitalization, the enterprise local area network used for production management is closely connected with the fieldbus network for automatic control, and digital signals High precision, strong anti-interference ability, and high reliability of the entire system; ②Fully distributed, realizing intelligent field equipment and distributed control of the system; Upload the self-diagnosis information to the main control room and have strong independent working ability, which improves the reliability and fault tolerance of the whole system; ④Reduces the amount of wiring engineering, and the equipment is connected to the bus network; ⑤The system is open and interoperable, and conforms to the The products of different manufacturers of international standards can be integrated and used, which reduces the cost of the control system.

3.2 Application of Siemens fully integrated automation technology based on PROFIBUS to form a monitoring system

According to the characteristics and scope of application of the field bus control system, combined with the actual situation and technical requirements of this project, the PRO-FIBUS field bus control system is adopted. Figure 2 is a network structure diagram of the monitoring system.

The system is composed of a complete set of computer monitoring network with PLC as the core and open fieldbus network as the main structure. It is divided into three levels: ①Control master station layer; ②ProfibusCDP backbone network layer in the warehouse area; ③Actuator, sensor layer.

3.2.1 Control the master layer

The master station layer adopts SIEMENS PLC module, CPU414CDP, and communicates with the network through CP443C5 module. The master station PLC (which can be multiple PLCs that cannot control each other but can transmit data to each other) is connected with the upper PC to form the master control center. The engineer station is used for the configuration and maintenance of each field slave station, and the operator station completes the control of the oil tank. Various parts of the operation monitoring, data acquisition and other automatic detection system scheduling functions. The master station is equipped with a printer for report printing and alarm printing. The overall C/S structure is adopted, and the system server is hot-standby to increase the reliability of the system. It is connected to the entire enterprise office management system through industrial Ethernet and upper-layer communication. This layer is the dispatch core of the entire oil depot monitoring system.

3.2.2 PROFIBUSCDP backbone network layer in the library area

The trunk layer of the reservoir area adopts PROFIBUS, selects 4-core optical fibers, and connects redundantly, and all sub-stations pass through. PROFIBUS is connected to the main station to realize data collection and information exchange. The temperature, liquid level, flow, pipeline pressure, video signal and solenoid valve signal of each tank farm are transmitted to the main station.

3.2.3 Actuator and sensor layer

ASCi is the actuator-sensor interface, which is a bus network for bidirectional exchange of information between the main controller and the sensor/actuator, and it belongs to the underlying network of the field bus. It is connected with PROFIBUS through the gateway. The gateway is a node of the upper bus, and a batch of ASCi slave stations can be attached below. The ASCi bus is mainly used for sensor/actuator systems with switching characteristics. The sensors can be various remote proximity switches and temperature, pressure, flow, liquid level switches, etc. The actuator can be various switch valves, sound and light alarms, or other electrical appliances. There are two ways for sensors/actuators to be connected to the ASCi bus. One is an intelligent A/S with an ASCi communication interface, which is equipped with a dedicated chip for ASCi modules and is directly connected to the ASCi bus; the other is an intelligent A/S with an ASCi communication interface. It is distributed and connected by special ASCi interface module and common A/S. ASCi cable adopts 2-core flat cable. The piercing installation presses the wire on the connector, which is simple and reliable. It is made of special synthetic rubber as an insulating protective layer. When it is pulled out from the connector, the perforation is automatically closed, so it can Repeated use, it not only transmits messages, but also provides power to circuits such as A/S through the network.

As shown in Figure 3, the ASCi bus is connected to the PROFIBUS-DP bus through the SIEMENS DP/ASCi link module. This coupler is the PROFIBUS-DP slave device and the AS-i master device, which can connect up to 62 ASCi slave devices. Station modules, the status of these slave modules is displayed by the LEDs of the DP/ASCi link module. The DP/ASCi link module is powered by the ASCi flat cable and requires no additional power supply. The K45 and K60 modules in Figure 3 are field-installed ASCi interface compact modules with protection class IP65/67. There are digital, analog and pneumatic types, and are connected to sensors/actuators through A/S connectors.

The PROFIBUS-DP fiber optic network with OLM fiber optic link module will not be damaged due to external interference fields due to the use of optical signal transmission, without grounding problems, and achieve electrical isolation, which is of great benefit to the safety of the tank area, and is light in weight, Easy to install. The OLM optical fiber link module has industrial twisted pair (ITP) and FOC (optical fiber) interfaces. Through the FOC interface, several OLMs can form an optical fiber ring network as shown in Figure 2.

3.3 Selection and configuration of PLC

In order to ensure advanced technology, easy operation and convenient subsequent expansion, Siemens S7-400 series PLC products are used in the design. It has a modular structure, strong expansion functions, sturdy structure, high reliability, comprehensive functions, fast running speed, and powerful functions. The communication capability and integrated system functions are convenient to use, and it is suitable for monitoring projects such as oil flow and tank wall pressure in oil depots. The oil depot has many data acquisition and status monitoring and more program control. S7-400 is used as the master station, and communicates with the PROFIBUS network through the CP443-5 communication module, and the field signal is transmitted to the master station through PROFIBUS.

Design of oil depot monitoring system based on Siemens PROFIBUS and ASCi bus technology

S7-400 can plug and unplug input/output modules under power, and modules can be replaced during operation to ensure continuous and uninterrupted operation of the system. The main performance indicators of S7-400 are as follows: ①Program operation speed, bit and integer operation 0.1/μs, floating point operation 0.6/μs; ②I/O function, DI/DO: 65536, AI/AO: 4094; ③User memory, 128 kB is used for program, 128 kB is used for data, can be extended to 15 MB; ④ general interface, multi-point interface MPI, PROFIBUS-DP: 12Mbit/s.

3.4 Software Settings

The PROFIBUS-DP bus has 7 stations in total, of which S7-400 is the master station, and the rest are slave stations. STEP7 is used to assign addresses to each station to configure the system, and to parameterize the modules that can be set. To configure the communication, make sure that the parameters match correctly so that the network actually establishes communication.

The industrial computer monitoring software WinCC is based on the man-machine interactive monitoring system and runs on the Windows platform. Its powerful process interface interface and high security data archiving characteristics are suitable for the operation and monitoring of the oil depot process and control process. The software directly connects the PLC information to the user’s application graphics according to the data information established by the user. The operator can monitor the status and operation data of the oil depot through the operation screen and flow chart, issue control commands, and can also perform parameter modification, fault handling reset, report printing, etc. to achieve automatic management. The main operation screens are: ①The general layout of the oil depot project; ②The process flow of the oil depot and the simulated static and dynamic diagrams; ③The automatic control system and electrical wiring diagram of the oil depot project; , and the alarm summary list is displayed.

4. Summary

At present, most of the smart meters with bus interface are imported, and there are many traditional equipment in oil depots, so it is difficult to achieve a full bus system overnight. This monitoring system takes PROFIBUS as the backbone of the system and the integrated structure of the ASCi bus as the supplement to solve this contradiction to a certain extent, which is suitable for the current situation of oil depots in my country. The system has good integrity, safety and reliability, complete functions, convenient operation and maintenance, and has been well received by users after application. The automation of the entire oil depot is a very complex system with a large investment and it is difficult to achieve it in one step. It should be overall planned and implemented gradually when transforming and rebuilding the monitoring system of the oil depot.