PVC pipe extrusion melt pump core technology analysis
The PVC pipe extrusion process is demanding on melt pumps, which are characterized by structural design, performance adaptation and material selection, etc. I will summarize the core characteristics of PVC pipe extrusion melt pumps from these dimensions. I will start from these dimensions to summarize the core characteristics of PVC pipe extrusion melt pumps:
1. Structural design adapted to the characteristics of PVC processing
PVC pipe extrusion melt pump adopts special structural design. In order to cope with the poor fluidity of PVC melt, easy to decompose, the internal flow channel of the pump body adopts a large diameter, short flow channel to reduce the residence time of the melt in the pump, to avoid corrosion of the equipment due to the decomposition of hydrogen chloride gas generated by high temperature. At the same time, the gear adopts involute or asymmetric tooth shape to reduce the melt shear rate and prevent the PVC melt temperature from rising suddenly due to excessive shear, so as to ensure the stable quality of the pipe.
2. Outstanding corrosion and abrasion resistance
PVC will release trace hydrogen chloride gas during processing, which is corrosive. Therefore, key parts of the melt pump, such as gears and pump body, are made of duplex stainless steel or surface-hardened alloy steel, with Viton or PTFE seals to effectively resist corrosion. In addition, considering the abrasive nature of fillers such as calcium carbonate that may be contained in the PVC raw material, the melt pump enhances the wear-resistant performance and prolongs the service life of the equipment by improving the surface hardness of the gears (up to HRC60 or above) and optimizing the roughness of the tooth surface (Ra ≤ 0.8μm).
3. Advantages of precise metering and pressure stabilization
PVC pipe has strict requirements on wall thickness uniformity, and the melt pump needs to have accurate metering and pressure stabilization. It adopts high-precision gear processing and assembly technology, gear meshing clearance control in 0.03 - 0.05mm, volumetric efficiency of more than 95%, can control the export pressure fluctuations within ± 0.5MPa, to ensure that the pipe wall thickness tolerance within ± 0.1mm, to meet the requirements of national standards. At the same time, through the frequency conversion motor drive, the flow rate can be adjusted in real time according to the extrusion speed to ensure the continuity and stability of the production process.
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