Centrifugal pumps will gradually wear and corrode their impellers due to the erosion of sediment, water flow, and corrosion of the medium. The surface of the blade often forms grooves or streaks, or is damaged by cavitation, resulting in honeycomb like holes or even perforations on the blade. If the blades are cast with pores, sand holes, or slag inclusions, the surface is prone to pores and even cracks after operation.
There are various methods for repairing water pump impellers, and there are many methods for repairing impeller cavitation, such as using ARC polymer composite material coating, powder coating (welding), epoxy resin coating, rubber, nylon composite material repair, etc., as well as using stainless steel inlay, welding, etc. The use of epoxy resin polymer material coating has the advantages of simple construction method, low cost, and good effect.
By optimizing the ratio and adjusting the performance indicators of the material in a targeted manner, it demonstrates high-strength adhesion and toughness in absorbing impact energy, and has high strength and hardness in resisting cavitation and abrasion damage.
Common repair methods:
1. Copper wire repair method
For needle shaped cavitation, as long as the holes are not connected into pieces, a copper wire can be used to punch the needle holes and file them with a file. Before processing, use a polishing machine to remove rust and dirt from the surface of the blade. Then, use an oxyacetylene flame to blow away debris from the pores. Fill the pores with copper wire of appropriate thickness, and strike them with a pointed hammer to squeeze and compact the copper wire into the hole. Finally, file it flat with a file.
2. Gas welding repair method
Heat the impeller on a charcoal fire to 400-500 ℃, hang tin at the welding repair site, and then melt the brass wire into the groove or hole that needs to be repaired with an oxyacetylene flame. After welding, remove the charcoal fire and cover it with asbestos board for insulation, allowing the blades to cool slowly to avoid cracking. After welding repair, use a file to process and trim according to the original contour line.
3. Rapid Steel Repair Method
Rapid steel is a type of adhesive repair agent that is in the form of a paste before curing. After curing, it has high strength, hardness, no shrinkage, and no corrosion. It is suitable for filling and repairing pores, cracks, sand holes, and other areas in metal materials such as steel and iron, and has a strong bonding effect. Before repairing, clean up any floating rust, dirt, etc. around the area to be repaired and roughen it. Take out the colloid in the quick formed steel plastic pipe, quickly and fully knead the two materials with different colors of the inner core and outer skin of the colloid into one color (about 1~2min) by hand, and it is better to reach a warm and soft color (official account: pump steward). Before the rapid solidification of the steel gel, it should be firmly adhered to the repair site and compacted multiple times (by hand or tool) during the solidification process to enhance the adhesion between the gel and the blade. After the rapid hardening of the steel, file it flat with a file.
4. Epoxy resin repair method
Mix an appropriate amount of epoxy resin, ethylenediamine, dibutyl phthalate, and acetone in a glass container according to the mixing ratio and order, and mix well. When stirring, pay attention to the viscosity of the adhesive and add an appropriate amount of acetone. The prepared epoxy resin should be used up within 20-30 minutes. Dip a wool brush into epoxy resin and apply it to the sand holes and air holes on the surface of the blade. When applying, gently squeeze out the bubbles in the middle of the sand holes and air holes with a pointed cone, and try to apply evenly and firmly. At the same time, gently scrape and compact with a scraper. After 1-2 hours of curing of the epoxy resin, brush it 2-3 times. When painting for the last time, make sure to make the surface of the blade smooth and even. After painting, place the impeller in an environment with 20-30 ℃ and low relative humidity, and slowly cure for 48 hours. After the epoxy resin is completely cured, use a file or polishing machine to trim the contour line of the impeller and the protrusions on the surface layer.
5. Welding repair method
Before welding, use a grinding machine to polish the eroded area and clean the surface of rust and debris until a shiny metal body is exposed, in order to make the welding layer and blade more firmly bonded. After cleaning, preheat the impeller by placing it in charcoal fire. Use welding rods or stainless steel welding rods with the same material as the blades, without peeling or damage, keep them dry, remove moisture, and prevent porosity during welding. When welding, back and forth welding should be used, or layered cross pressure welding can be used. The amount of welding each time should be small to prevent the blades from being heated and concentrated, resulting in stress deformation. After welding, use a polishing machine to trim the blades. The repaired impeller must undergo a static balance test. To prevent centrifugal force from causing vibration of the water pump due to the imbalance of additional weight when the impeller rotates at high speed.
