Abstract: The current waste thinner recovery system in the intermediate and top paint spraying room adopts the recovery method of pumping the waste liquid in the paint spraying room recovery tank into the waste liquid tank in the paint mixing room through the action of the pneumatic diaphragm pump after the waste liquid flows by gravity to the recovery tank in the paint spraying room. Due to the influence of many factors,such as the characteristics of the cleaned thinner,the direction of the pipeline and the long-term use,the waste liquid recovery pipeline is often seriously blocked,causing the recovery device not being able to operate normally. To solve the problem of drying due to the increased viscosity of waste liquid in the recovery pipeline,the recovery mode and circulation mode of waste liquid pipeline shall be switched frequently to ensure the normal operation of the recovery system to a greater extent and improve the recovery rate of waste liquid as a whole.

Key words: waste liquid viscosity, recovery pipeline, circulation system, mode switching