Causes of pump jamming of polyester melt metering pump

　　When the driving torque of the melt metering pump increases gradually due to external factors, exceeding the rated shear moment of the safety pin of the protection metering pump, the safety pin breaks, the production stops, and the pump is stuck. It can be seen that the cause of pump sticking in melt metering pump is that the driving torque gradually increases, that is to say, the resistance between parts with relative motion in melt metering pump is increasing. The gap between pump shaft 7 and the inner holes of pump plate 1, pump plate 6 and pump plate 3 is controlled within a reasonable range, and the high-pressure melt film is filled in the gap, so that the concentricity of pump shaft and cover plate is always in an ideal state, and the increase of driving torque of melt metering pump caused by the concentricity deviation between pump shaft and pump plate can be ignored.

　　The reason for the increase of friction force is the poor lubrication effect at the relative moving parts. The most direct way to judge whether the lubrication effect is good or not is to observe the state of lubricating melt discharged from the pump head of the metering pump. The state of lubricating melt discharged from pump head is divided into liquid melt, solid melt and non melt. It has been proved by practice that the metering pump with continuous discharge of liquid and solid melts from the pump head will never be stuck;