Re-Welding of Shaft Journals of Large Electric Motors
Meeting the Increasing Demand for Advanced High Torque Electric Motors
The demand for advanced electric motors that can produce higher torque is ever increasing, as new and more efficient machines are designed for large industrial applications. To ensure long-term reliability for these devices, special attention must be given to the re-welding of the motor’s shaft journals. This process involves re-welding the journals with a combination of different welding methods, including shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW).
First, the surface of the shaft journals must be inspected and prepared prior to welding. This process includes grinding off any surface oxide layers, and ensuring that the journal’s underside is completely free of dirt, oil, and grease. Depending on the type of material, the welding surface must also be inspected for any irregularities.
Once the surface is ready, the welded joint must be preheated to the proper temperature. Preheating is done using a torch or a resistance welder, which is used to heat the metal to the proper temperature. This step helps reduce the risk of cracking, which is especially important when welding thick metals and large shaft journals.
After the joint is properly preheated, two Weld passes are performed. The first pass is typically the root pass, which is a bead of weld metal filled into the groove between the journals. The second pass is usually a cover pass, which is a bead of weld metal that is deposited over the root pass to provide further support and strength. During these passes, proper shielding gas must be used and the arc temperature must be carefully monitored to ensure weld quality and consistency.
Once the first two weld passes are complete, the joints must be ground down to the desired shape and size. This involves carefully grinding down the journal grooves so that they are flush and meet manufacture specifications.
Finally, the welded joint is tested and inspected to ensure that the weld quality is up to standard and meets any additional requirements. Oftentimes, non-destructive testing methods are employed, such as radiographic (x-ray) or ultrasonic testing. These tests highlight any hidden flaws or imperfections that were missed by a visual inspection. If any issues arise during these tests, the welded joint must be re-welded and corrected.
Re-welding of the large electric motor shaft journals is a critical process that helps to ensure the safety and efficiency of a motor system. Through careful grinding, welding, testing, and inspection procedures, these shaft journals can be re-welded to create a strong, reliable, and long-lasting joint.
