Application of displacement closed loop control system based on HMI and PLC in automatic anti-corrosion coating production line for large steel pipes

FAN Lie-peng1， SHI Hai-qin2， LEI Jun2
（1. Ningbo Xiangshan Corrosion Control Engineering Co.， Ltd.， Ningbo 315010， China；
 2. Zhejiang Longkey Corrosion Control Technology Co.， Ltd.， Ningbo 315010， China）

Abstract： Aiming at the problems of uneven film thickness of large steel pipe anti-corrosion coating and large loss of paint due to the speed change inequality of large steel pipe on the automatic coating line，the human machine interface（HMI） and programmable logic controller（PLC） control system and speed measurement equipment of laser displacement sensor were applied in large steel pipe automatic anti-corrosion coating line for closed-loop control of steel pipe moving speed to keep uniform speed of steel pipe running. The film thickness changes of large steel pipe anti-corrosion coating before and after closed-loop control were tested in the case of the same spray parameters through practical application analysis and contrastive measurement of the speed history curve of open-loop and closed-loop. The results indicate that the displacement closed-loop control system based on HMI and PLC can effectively improve the problems of uneven film thickness and large loss of paint due to the speed change inequality in the process of large steel pipe running. The film thickness change rang is reduced from ± 30% down to about ±10%，which means that the displacement closed loop control system based on HMI and PLC in automatic anti-corrosion coating production line for large steel pipes is feasible.
Key words： human machine interface（HMI）；programmable logic controller（PLC）；closed loop control；anti-corrosion coating