在整个PLC控制系统中，容易发生故障的地点在现场，现场容易在以下几个方面出故障。

1、一类故障点也是故障多的地点)在继电器、接触器

如某生产线PLC控制系统的日常维护中，电气备件消耗量大的为各类继电器或空气开关。除了产品本身质量原因之外，主要是由于现场环境比较恶劣。例如，暴露于生产环境中的接触器触点易打火或氧化，逐渐发热变形，直至不能使用。该生产线所有现场的控制箱都是选用密闭性较好的盘柜，其内部元器件较其他采用敞开式盘柜内元器件的使用寿命明显要长。所以避免此类故障应尽量选用高性能继电器，并改善元器件使用环境，就可以减少更换的频率，降低对系统运行的影响。

2、二类故障多发点在阀门或闸板这一类的设备上

因为这类设备的执行机构相对位移较大；或者传动结构复杂，机械、电气、液压等各环节稍有不到位就会产生误差或故障。在长期的运行状态下，如果缺乏运行维护，易造成阀体部件的卡，堵，漏等现象。因此在系统运行时要加强对此类设备的巡检，发现问题及时处理。我厂对此类设备建立了严格的点检制度，定期检查阀门是否变形，执行机构是否灵活可用，控制器是否有效等，很好地保证了整个控制系统的有效性。In the whole PLC control system, the site is the most prone to failure, and the site is the most prone to failure in the following aspects.



1. The first type of fault point is also the most fault point) in relays and contactors



For example, in the daily maintenance of the PLC control system of a production line, the largest consumption of electrical spare parts is various relays or air switches. In addition to the quality of the product itself, the main reason is that the site environment is relatively bad. For example, the contacts of contactors exposed to the production environment are easy to ignite or oxidize, and gradually heat and deform until they cannot be used. All on-site control boxes of the production line are made of panels and cabinets with good tightness, and the service life of its internal components is significantly longer than that of other open panels and cabinets. Therefore, to avoid such failures, high-performance relays should be selected as far as possible, and the use environment of components should be improved to reduce the frequency of replacement and reduce the impact on system operation.



2. The second type of fault frequently occurs on equipment such as valves or rams



Because the relative displacement of the actuator of such equipment is relatively large; Or the transmission structure is complex, and if the mechanical, electrical, hydraulic and other links are not in place, errors or faults will occur. Under long-term operation, if there is no operation and maintenance, it is easy to cause jamming, blocking and leakage of valve body parts. Therefore, when the system is running, it is necessary to strengthen the patrol inspection of such equipment and timely handle the problems found. Our factory has established a strict point inspection system for such equipment, regularly checking whether the valve is deformed, whether the actuator is flexible and available, and whether the controller is effective, which well ensures the effectiveness of the entire control system.