As the key equipment in the continuous polyvinegar production line, the stable and long-term operation of the melt pump is of great significance to the continuous stability of the whole production line and the improvement of production efficiency and economic efficiency. Melt pumps are mainly used for melt transportation, pressurization and metering in synthetic resin polymerization units. It has the characteristics of compact structure, reliable operation and low energy consumption.

　　Since the installation and operation of three melt pumps of PET and PBT devices, the pressure sensor of pump head has not been displayed accurately, and the adjustment of pressure only depends on the experience of maintenance personnel. The journal and packing of the melt pump in our unit are dynamic seals, which are easy to leak. They play a key role in packing seal pump and pressure regulating valve. Generally, if the pressure is higher or lower than the range of parameters, the normal operation of the melt pump will be affected. If the first line of the pressure regulating valve comes out, the silicone oil of the lubricating sealing filler or the outside air will enter the solution of the melt pump, and there is air hammer sound in the gear pump.

　　The hazards caused by air entering into the process system are as follows: first, the swing of the strip will even break the wire, which will affect the appearance quality of the slice; second, if the strip breaks, the stacking of the diversion tank of the granulator will occur if the operator does not clean it up in time; third, the filler lubricant (silicone oil) will all enter the slurry. If the pressure regulating valve is basically closed (when the pump pressure is higher than 0.5 mpa, the second line is even), the solution in the pump body will leak through the labyrinth ring and packing layer, that is to say, the melt will leak out. Slurry will flow to the outside world through labyrinth rings, fillers and sealing interval loops. The greatest harm is to block the lubricant (silicone oil) guide groove and guide hole on the sealing interval ring. Slurry will solidify on the sealing interval ring, and the outside lubricant (silicone oil) will not reach the surface between the filler and the bush. Long time without lubricant (silicone oil) lubrication. Long time dry friction between sleeve and sealing filler will lose the inherent characteristics of filler, will lose the role of friction seal with sleeve. The closer sliding bearing is to mixed friction, even dry friction, the more serious damage to the shaft and bearing surface.