Specific measures to solve side wall wear of melt pump
The volume loss of the melt pump is inevitable in the process of transportation, which mainly includes: (1) leakage of the axial clearance (that is, the end clearance of the gear). (2) Leakage of radial clearance. (3) Leakage of gear meshing point. (4) Elastic loss in liquid compression.
The axial clearance of the melt pump refers to the clearance between the end face of the gear and the side plate or the end face of the bearing. The melt leaking through this clearance flows into the bearing chamber and returns to the entrance side. Because there are many ways of axial clearance and the length of sealing liquid is short, the leakage of the axial clearance accounts for 70-80% of the total leakage, so reducing the leakage of the axial clearance plays a decisive role in reducing the volume loss and improving the volume efficiency. In high and medium pressure melt pumps, it is common to adopt hydraulic automatic compensation structure with axial clearance.
The axial clearance hydraulic automatic compensation of melt pump mostly uses floating side plate (or floating axle sleeve) and a few uses flexible side plate. Under the action of hydraulic pressure, the side plate is close to the end face of the gear, which reduces the axial clearance. When the end face is worn, it can be automatically compensated to keep the axial clearance basically constant. However, in high-pressure melt pump, it is not feasible to adjust the clearance by using floating sleeve, side plate, radial sealing block and other structures, because this will cause material to decompose due to the long residence time in the pump.