The impeller is the main working component of the marine centrifugal pump. It plays a large role in the safe and economic operation of the marine seawater pump. The impeller repair usually has the following contents.
1. Impeller seal ring wear
During disassembly and overhaul, it is often found that there are different degrees of wear outside the impeller ring. If the degree of wear is within the allowable range, the inner hole of the impeller can be swollen on the lathe with a special tire, and the worn part can be turned and configured. Corresponding seal ring and vane bushing to maintain the original clearance. After the impeller ring is trimmed by the lathe, in order to prevent the heart from being displaced during the machining process, the concentricity of the impeller ring should be checked. An optical axis with a shoulder can be inserted into the inner hole of the impeller, the optical axis is fixed on the vise, and an angle is raised, so that the end face of the hub on the suction side of the impeller always contacts the shoulder of the tire to slowly rotate the impeller. The runout value indicated by the dial of the impeller ring shall not exceed the standard of Table 3. If the runout value is greater than this standard, mark the large amount of bounce to facilitate turning repair. After the repair, it should be checked again until the round jump amount meets the requirements. For some centrifugal pumps with a sealing ring on the circumference of the balance chamber, the back of the impeller also has an outer circle of the impeller that is subjected to the friction of the seal ring or a friction ring mounted on the outer circle. The radial circle on the circumference should also be checked during inspection. The amount of runout, the method and standard are the same as the above-mentioned ring.
2. Impeller erosive damage
The blades of the first stage impeller of the marine pump are easily damaged by cavitation. If there is a slight cavitation hole on the blade, repair welding can be performed. Epoxy adhesives are used to repair the impellers that are cavitation. The most effective repair processes include:
1 Derusting the rotted hole of the impeller and its surrounding surface, and grinding it with a fine abrasive cloth;
2 The order of preparing the epoxy binder is: heating the epoxy resin to 30~40 °C, making it easy to mix, and then adding the plasticizer dibutyl phthalate, filler iron powder and chromic oxide And they are evenly shaken, and the curing agent B hydroxyethylenediamine is placed when it is repaired;
3 Apply the prepared epoxy adhesive to the surface around the rotten hole quickly and evenly. Immediately apply the glass cloth evenly and evenly to the applied epoxy adhesive to cover the hole and then at room temperature. It can be used after curing for 24 hours.
3. Loose fit between the impeller and the shaft
Due to long-term use, multiple assembly and disassembly, the gap between the inner bore and the journal of the impeller is too large, which will affect the concentricity of the impeller, increase the radial runout of the impeller, and cause the rotor to vibrate after assembly. . If the gap is found to be large, it can be trimmed with a lathe after spot welding in the inner hole of the impeller, or it can be chrome-plated and then ground. If the impeller fails to meet the quality requirements after the above-mentioned maintenance method is adopted, the impeller needs to be replaced. For the new impeller, first check whether the geometrical dimensions match the original design, then clean the flow path of the impeller, and require the surface to be smooth, and each new impeller needs to be statically balanced before being used.
