Dec. 10, 2010
-- One of the projects involved reclaiming land from the sea had a sophisticated design and foundation, and construction of an oil refinery plant with annual capacity of 21 million tons of crude oil, naphtha cracking plants that produce 1.735 million tons of ethylene per year, a thermal power plant that can output 3 million kilowatts of energy, and other petrochemical plants. A naphtha cracker is a plant that uses a "cracking process" to produce ethylene from naphtha. The major control problem associated with naphtha crackers is to regulate the conditions in the cracking process to control the ethylene output. One of the many challenges faced by the designers of "No. 6 Naphtha Cracker" was creating an extra-reliable Ethernet network for transmitting significant control and device management signals. The network serves as the main communications medium for the plant's distributed control system. The DCS used for controlling the main processes at the No. 6 Naphtha Cracker is made up of several subsystems for handling different parts of the operation. The central IT room, for example, containing LCD monitors for displaying the HMI/SCADA system, has a number of work stations for data processing, plus a data server for controlling and monitoring I/O controllers located at a remote site. In order to optimize the manufacturing output from the Naphtha Cracker, the conditions in the cracking process need to be monitored and controlled. Remote I/Os are typically used to connect DI/DOs or AI/AOs, temperature modules, and motors to detect temperature, pressure, humidity, and other operation related information. In addition, controllers are connected to remote I/Os and motor servers to maintain better control of the process. In order to set and adjust parameters on-site, control panels are located in the field to allow engineers to access or check information directly. As is the case with most sophisticated industrial control systems, the DCS at the No. 6 Naptha Cracker must maintain normal operation 24 hours a day, 7 days a week to keep production running smoothly. The system designer adopted Ethernet as the main communication network for the entire DCS. Eight sets of Moxa EDS-726 modular Ethernet switches were applied to form a doubly redundant fibre network backbone with dual-tree topology for better reliability. The EDS-308- MM-SC 8-port unmanaged Ethernet switches were used to form the communication network between the system backbone and operation stations. There are two parallel but independent Ethernet networks, with each network device connected to both networks (e.g., each workstation has two network cards). In addition, the entire array of workstations and devices is duplicated; at any given time, one set is "active" and the other set is "stand-by." When a device in the "active" set fails, the "stand-by" set springs into action, taking over operation until the other set is repaired. Moxa's EDS switches are available with a variety of fibre and copper port combinations, and the reliable industrial-grade quality of the switches helps users maintain a reliable gigabit backbone and communication network for synchronizing data exchange and optimizing the manufacturing output. DCS systems networked with Moxa's EDS switches improves manufacturing productivity and helps users achieve a competitive advantage.
Benefits: The EDS-726 switch's modular design makes it easy to maintain and upgrade. High port density offers greater versatility and to maximize connections at field sites. Moxa provides Class I, Div. 2 (Zone 2) certified Ethernet products that are well suited for applications located at hazardous petrochemical plants. High MTBF and greater reliability for long-term operation. Multi/single-
mode fibre for long distance communication needed at large-scale plants. Versatile port combinations that provide a wide variety of options for different applications. SNMP V1/V2C/V3, RMON for better monitoring and control over the network
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