Analysis of screw wear of screw pump

2022-10-10 20:58:35

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Screw pump The main reasons for the wear of the screw rod are as follows:

1. Each kind of plastic has an ideal processing temperature range for plasticization. The barrel processing temperature should be controlled to make it close to this temperature range. When granular plastics enter the charging barrel from the hopper, they will first reach the charging section, where dry friction will inevitably occur. When these plastics are not heated enough and melting is uneven, it is easy to cause increased wear on the inner wall of the charging barrel and the screw surface. Similarly, in the compression section and homogenization section, if the melting state of the plastic is disordered and uneven, the wear will also be accelerated.

2. The speed shall be properly adjusted. Some plastics are added with strengthening agents, such as glass fiber, minerals or other fillers. The friction force of these substances on metal materials is often much greater than that of molten plastics. When injecting these plastics, if the rotating speed is high, the shear force on the plastics will be increased, and the reinforcement will correspondingly produce more torn fibers. The torn fibers contain sharp ends, which will greatly increase the wear force. When inorganic minerals slide on the metal surface at high speed, their scraping effect is not small. Therefore, the speed should not be too high.

3. When the screw rotates in the barrel, the friction between the material and the two will gradually wear the working surface of the screw and the barrel: the diameter of the screw will gradually shrink, and the diameter of the inner hole of the barrel will gradually increase. In this way, the fit diameter gap between the screw and the barrel increases slightly with the gradual wear of the two. However, because the resistance of the head and the splitter plate in front of the barrel has not changed, this increases the leakage flow of the extruded material when it moves forward, that is, the flow of the material from the diameter gap to the feeding direction increases. As a result, the production of plastic machinery decreased. This phenomenon increases the residence time of materials in the barrel, causing material decomposition. If it is polyethylene, the hydrogen chloride gas generated from decomposition strengthens the corrosion of screw and barrel.

4. If there are fillers such as calcium carbonate and glass fiber in the materials, the wear of screw and barrel can be accelerated.

5. As the materials are not plasticized evenly or metal foreign matters are mixed into the materials, the torque force of the screw suddenly increases. This torque exceeds the strength limit of the screw, causing the screw to break. This is an unconventional accident damage.