Specific measures for melt pump leakage
Zhengzhou Batte is a large melt pump manufacturer in China, with decades of R&D and production experience, providing supporting equipment for thousands of domestic extruder manufacturers. The volume loss (melt leakage) is unavoidable in the process of melt pump transportation, which mainly includes: (1) leakage of axial clearance (that is, end clearance of gear); leakage of radial clearance; leakage of gear meshing point; and (4) elastic loss in liquid compression.
The axial clearance of the melt pump refers to the clearance between the gear end face and the side plate or the bearing end face. The melt leaking through this clearance flows into the bearing cavity and then returns to the inlet side. Because there are many ways of axial clearance and the length of sealing liquid is short, the leakage of axial clearance accounts for 75-80% of the total leakage. Therefore, reducing the leakage of axial clearance plays a decisive role in reducing the volume loss and improving the volume efficiency. In the medium and high pressure melt gear pump, the use of axial clearance hydraulic automatic compensation structure is more common.
Melt pump axial clearance hydraulic automatic compensation, most of the floating side plate (or floating shaft sleeve), a small number of flexible side plate. Under the action of hydraulic pressure, the side plate is close to the end face of the gear, so that the axial clearance decreases. When the end face is worn, it can be compensated automatically to keep the axial clearance basically constant. However, in high-pressure melt gear pump, the use of floating sleeve, side plate, radial seal block and other structures to adjust the gap is not feasible, because this will cause material in the pump due to excessive residence time and decomposition.