Why Do Melt Metering Pumps Tend to Seize Up?
The root causes of melt metering pump seizure can be accurately traced back to three key factors: equipment, material, and operation. From the perspective of the equipment itself, prolonged continuous operation leads to accelerated wear on core wear-prone components such as gears and bushings, causing misalignment of clearance gaps and a significant decline in operational precision. Aging or damaged bearings directly cause rotational resistance, significantly increasing the likelihood of seizing. Additionally, if the internal structural clearances are poorly designed following thermal expansion of the pump body, metal components may interfere with one another, directly causing the metering pump to seize and shut down.
Material impurities and abnormal operating conditions are frequent causes of melt metering pump jamming. Hard contaminants such as metal particles and carbonized lumps mixed into the melt can easily jam the gear meshing areas; in particular, metal components like bolts and scrapers that detach from upstream equipment—such as the final shrink tank—not only cause jamming but may also directly damage gears, leading to more severe equipment failure. Additionally, localized solidification due to improper material temperature control, or decomposition and coking of material that has remained in the pump chamber for too long, leading to flow channel blockages, can also hinder the normal operation of transmission components, ultimately resulting in seizure failures.
Improper operation is also a major human factor contributing to the seizing of melt metering pumps. Failure to adequately preheat the system according to standards before startup can result in excessively high melt viscosity, causing a sudden increase in operating resistance and making the pump highly susceptible to instantaneous seizure. During production, insufficient feed at the inlet can cause the pump to run dry, leading to friction-induced heating that triggers thermal deformation and jamming of components. Failure to promptly remove residual material from the pump after shutdown allows the cooled and solidified melt to adhere to internal components, resulting in severe jamming failures upon restart.
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