In order to take the lead in the fierce competition in the dairy market, a dairy manufacturing company decided to expand and renovate its existing equipment. The success of this automation system transformation has made it a modern dairy company in Asia and the world.
In order to take the lead in the fierce competition in the dairy market, a dairy manufacturing company decided to expand and renovate its existing equipment. The transformation of the automation system includes: expansion of two original milk milk production line systems, transformation and increase of the milk processing pipeline of the standardized workshop, addition of two net milk machines (separators), addition of mixing and storage tanks to improve The ability of the entire standardized production workshop to increase the CIP cleaning line accordingly.
The basic guiding ideology of this transformation: not only to adopt the current popular automation control technology, but also to make full use of the PLC-5 programmable controller currently used, and at the same time can not affect the normal production of production, to achieve bumpless switching.
According to the structure and design experience of the domestic and foreign similar systems and the actual process control requirements, the control system adopts the ControlLogix5550 DCS system of Rockwell Automation. Including tank truck milk collection - net milk and separation - finished milk delivery preparation - service system (refrigeration and CIP) process parameters detection, setting, indicating alarm and adjustment control functions are all completed by the system.
The system uses Rockwell Automation's three-level network, the information layer uses Ethernet (EtherNet) to achieve system data exchange; the middle is the control layer (ControlNet, DH+) responsible for system communication; the bottom layer is the device layer, the network is connected to the local device, such as Valve box, inverter, etc. In order to improve production efficiency, process optimization, reduce costs, analyze various operations, and lay the foundation for safe production.
Process control computer
The system consists of 4 sets of ControlLogix and 2 sets of PLC5, 2 computer operation stations and 1 engineering station and one server through the network. Mainly complete the control of fresh milk storage, milk tanker cleaning (CIP TANKER), net milk and separation and the ratio of various milk products in the wet zone raw material tank, standardized production pipelines and transfer storage tanks (CIP HOT , CIP COLD) cleaning, preparation for the production of milk powder in the dry area.
The engineering station can perform software programming, configuration, download and online debugging on any PLC control station on the network through the network.
The operator station communicates with the PLC system via the EtherNet network to monitor the production process. Since the two operator stations are connected to the EtherNet, division of labor control can be achieved and the other can operate on its own when the fault occurs.
The server installs RSSQL and MSSQL software, which can collect data of each operation station. After processing the data according to requirements, it can realize fast and large amount of data exchange with the upper computer for the next operation.
System function: The whole system function realizes the process control of the dairy factory wet area from the beginning of milk collection until the end of the milk powder raw material ratio. These include: milk collection, net milk, standardization and CIP cleaning. The program design adopts sequential control technology. The program is strictly executed according to the process design steps, and the status of each valve and pump is detected in real time. If there is a fault, the program will generate an alarm signal, and the interlocking valves and pumps will act to ensure the system's safe operation.
1. Milk collection PLC
The five milk collection line milk tanker fresh milk is used for income measurement. Each milk collection pipeline has a terminal display operator PanelView at the site, and the setting of each step of milk collection is carried out through PanelView, including: tank number, contract number, etc. It is sent to the PLC for storage through the DeviceNet network. After the fresh milk passes through the cold exchanger, it is stored in the fresh milk tank.
2. Net milk machine PLC
According to different product requirements, the raw milk is controlled by net milk, separation and sterilization as raw materials for standardized production. The process setting of the net milk machine is mainly composed of five parts: start, preheat, cycle, production, CIP (cleaning in place) and so on. The net milk machine PLC completes the process control of four net milk machines (separators). In these five states, it includes the control of the feed and discharge valves, the slagging time setting and the control output and the adjustment control of the balance tank.
3. Standardized PLC
According to the formulation requirements of the milk powder product, the metering configuration of different raw materials is carried out in the standardized workshop, and the pipeline combination is selected for the same amount transmission. According to the requirements of the process, CIP COLD (HOT) is used to open the relevant pipeline valves and pumps to complete the pipeline cleaning.
4.CIP TANKER PLC
The cleaning of the milk tank truck is completed. The process includes cleaning the chemical tank, the water tank, the circulating water tank and the corresponding pipeline valve and motor. The three tanks serve as the source of the tank cleaning power on the five pipelines. Each milk collection pipeline has a PanelView at the site. The terminal display operator PanelView performs the setting of each step of CIP TANKER, and sends it to the PLC through DeviceNet to complete the control of each valve and pump related to the cleaning operation. It mainly controls the cleaning of 5 milk line tanks, automatic liquid refill control and liquid level detection alarm. Real-time fault detection of the valve and pump status, and depending on the type of fault, different control operations are applied to the valve and pump during the CIP process.
5.CIP COLD (HOT) STATION
Fresh milk, skimmed milk cans and pipelines are cleaned with CIP COLD; cream tanks and pipelines require higher temperature water and cleaning agents. CIP HOT is used. The process is basically the same as CIP TANKER PLC. Alkali tanks, clean water tanks, and circulating water tanks, these four tanks serve as the source of cleaning power for the five sets of combined pipelines, but the number of pipelines that need to be cleaned is relatively large. According to the different standardized transmission and milk collection pipelines, each group is composed of different pipelines. The CIP COLD (HOT) STATION communicates with the milk collection PLC and the standardized PLC to complete the cleaning of pipelines and tanks. Pipe valve and pump switch, PLC adopts PLC5-/40, PLC5-/60.
Control system features
1.ControlNet
The ControlNet network is a new generation of automation control network that meets the IEC61158 international industrial fieldbus standard. It provides a high-speed, redundant communication between PLCs, MMI operator stations and I/O subsystems. It can support up to 99 nodes with a maximum network distance of 20KM, which can connect different network topologies such as bus type, tree type, star type and hybrid type. ControlNet enables key data transfers, I/O updates, processor interlocks, peer-to-peer communications, and more on a single network. The Producer/Consumer communication mode allows signals to be exchanged between different processors, and I/O data can be shared by multiple devices at the same time. The expansion module and remote I/O module can be directly hung on ControlNet, so that the control module is most likely to be close to the field detection component, reducing the attenuation and interference of detection and control signals, while saving cables and facilitating maintenance. The PLC connects the main control equipment ControlLogix, PLC5, etc. through ControlNet.
2.EtherNet
The EtherNet network is a Windows NT network composed of TCP/IP between the operation station and the server. It has the ability of data and file sharing. It manages the history, real-time data and files of each operation station through a unified database interface (ODBC). It is convenient for production scheduling and can be further integrated.
3.DH+
It is a local area network that supports remote programming of factory application engineering, and can also transfer data between programmable controllers, computers, man-machine interfaces, etc. through DH+. All enhanced PLC-5s have a built-in DH+ communication interface. Each link of the DH+ network can connect up to 64 devices. It can be used for the on-site monitoring equipment PanelView, PLC-5 and ControlLogix PLC in the wet zone connection area.
4.DeviceNet
The DeviceNet network is an open, low-level communication connection that connects simple, industrial devices to advanced devices. DeviceNet features interoperability, public networks, low maintenance costs, and saved network cabling. Connect remote FLEX I/O to control field valve box and frequency converter.
The automation system from DeviceNet to DH+, ControlNet and EtherNet has a clear structure and functional grading, which improves communication speed. The control data and information of the wet area are integrated through the three-level network and network interfaces at all levels, and transmitted to the management and production departments at all levels.
Design implementation
Rockwell Automation's three-layered network structure enables the transformation and new automation functions to form a unified structure. At the device level, devices with DeviceNet interface reduce cost, reduce wiring, and facilitate installation. At the control layer, the system implements real-time I/O control, interlocking, and status transfer, thus ensuring real-time control data and information. Stability; at the information layer, control data is passed through the gateway to the enterprise's information system.
1. Human-computer interaction interface
The characteristics of dairy production are more equipment, long control distance and poor electromagnetic environment, so the connection communication and operator interface of the control equipment are demanding. The transformation of the standardized control center dispatching monitoring system in this transformation adopts InTouch7.1 monitoring software and ControlNet communication mode, real-time monitoring system, with production management function, real-time data collection for the production process of the main production links and auxiliary links in the wet zone, Select, operate, transfer, batch, clean, display, print; the host computer uses DELL computer, providing a friendly man-machine interface and convenient operation. The screen includes: net milk machine, each CIP station, milk collection, standardized process screen, operation screen, adjustment screen, trend screen, alarm screen, group screen, report screen.
2. Communication network
Due to the Ethernet network technology used in the PLC network, many PLC products support the Ethernet TCP/IP communication protocol, which can integrate the control system with the information management system and monitor the programmable control through the Ethernet network. Various data stored in the device, such data is used for data acquisition, monitoring, production management, equipment maintenance, production process and material ratio, etc. At the same time, TCP/IP protocol can enable computer access to use structured language (SQL) Open database for easy storage and query and report formation.
3. Undisturbed switching input
Fresh milk is not easy to store. In order not to affect the normal and continuous production, we use the “disruptive switching input†method during the implementation of the project. In the original production, CIP COLD PLC has only four main lines of A, B, C and D. This time, it is expanded into five groups. The combination of each group is different from the original, and the branch combinations included in each group are also increased. It brings great difficulties to the expansion of the control station.
According to its pipeline and process characteristics, you can make full use of communication network resources. On the communication DH+ network contact, establish a new PLC-5 station; use the new pipeline combination selection to carry out software programming and communication between the host computer and other controllers, perform program logic control on the PLC, and output the program. The automatic control bit is temporarily shielded. Through network communication, the software communicates with the MSG command, and the automatic control bit is transmitted to the original PLC station. The PLC only performs the output action, and there is no logic control, which is equivalent to only one "I/. O†equipment, realize I/O conversion; as the process pipeline increases, the I/O control point of the program gradually corresponds to the actual new I/O, and the function of the original PLC is replaced by the new PLC to realize the logic switching. After completing the bumpless switching, the program part of the old PLC is modified and transformed into a CIP HOT STATION control station to realize the new control station input.
Conclusion: After this expansion and transformation, the automation control system of the entire wet area realizes more comprehensive automation, information centralized monitoring and management information. The success of this automation system transformation has made it a modern dairy company in Asia and the world. At the same time, it has enhanced the market competitiveness of enterprises and succeeded in the fierce competition in the world dairy market.
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