FOXBORO AD202MV controller
The maintenance content of DCS is numerous and complex, so when there are faults, it is easy to have no clue. Generally, common faults can be started from the following eleven directions:
1. Communication network failure
Communication network faults are generally prone to occur at the contact bus, local bus, or due to address identification errors.
2. Node bus fault
The transmission medium of the node bus is generally coaxial cable, some using token signal transmission method, and some using a collision detection based multi channel contention bus signal transmission method. Regardless of the method used, any interruption in the main line of the bus will result in communication failures between all stations and their sub devices on that bus.
At present, the general method to prevent such faults is to adopt a dual redundant configuration to avoid affecting the overall situation due to a fault on one bus. However, this cannot fundamentally prevent the occurrence of faults, and once one bus fails, it is very easy to cause another bus fault during processing, and the consequences are very serious*** The method should start with preventing poor contact or open circuit of the bus. The most successful approach is the node bus layout of the system. The connection of the coaxial cable is not in front of the communication module, but behind the module. This way, when dealing with communication module faults during system operation, it can avoid accidentally touching the coaxial cable and causing network cable disconnection. At the same time, the coaxial cable will not be touched at any time except for * * * inspection, which can prevent loosening caused by multiple insertion and removal of the coaxial cable plug, increasing the possibility of its failure. In addition, a management system for coaxial cable inspection and replacement should be established, and replacement or handling should be carried out before the contact resistance increases to the point where communication is affected.
3. Local bus fault
Local bus or field bus – a data communication network typically composed of twisted pair cables. Due to the fact that the equipment connected to it is a primary component or control device directly connected to the production process, the working environment is harsh, faults occur, and it is easy to be affected by the misoperation of maintenance personnel and affect the production process. In addition, the bus itself can also cause communication failures for various reasons. The effective measure to prevent such faults is to first properly handle the connection points between the local bus and the local equipment. When disassembling equipment, it should not affect the normal operation of the bus. The bus branch should be installed in a place that is not easy to touch. At the same time, the bus adopts dual redundancy to improve communication reliability.
Foxboro provides factory automation systems, flow meters, single loop controllers, and various product support services. The company also provides level, pressure, and temperature instruments, as well as nuclear magnetic resonance (NMR) based process analyzers, for use in refineries, petrochemicals, food processing, and pulp and paper operations.
Foxboro Corporation was established in Foxboro, Massachusetts in 1908 and was acquired by Siebe PLC in Windsor, UK in 1990. In 1999, Siebe merged with BTR to establish Invensys plc. Foxboro is a brand under Invensys Systems, Inc. Foxboro/Inventys was acquired by Schneider Electric in 2014.
Foxboro is an extensive instrument supplier with a long-term reputation. In addition to its instrument product series, the company is also known for its I/A series, which was launched in 1987 as a Distributed Control System (DCS).
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