Can transformers be welded with oil for repair?

The repair of oil leakage in transformer welding lines is a crucial task for operating personnel. If welding repairs are conducted during a power outage with oil drainage, the transformer body remains inside the oil tank. As the insulation on the transformer body is already impregnated with oil, there will still be residual oil and gas in the tank. During arc welding repairs, the oil and gas are prone to combustion due to the heat generated by the electric arc. If the decision is made to completely dismantle the transformer for oil drainage and welding repairs, it entails a significant amount of dismantling work. Additionally, the transformer body, if exposed to the air for an extended period, needs to undergo re-drying, and the oil adhering to the inside of the tank must be cleaned through vapor flushing before welding repairs can take place. This results in substantial workload and prolonged power outage.

So, can repairs be carried out with oil present? The combustion of oil requires certain conditions, namely a specific temperature and an adequate supply of oxygen. When conducting repairs with oil present, although a substantial amount of heat is transferred to the oil through the tank walls, the oil undergoes convective heat dissipation, causing the high-temperature oil to rapidly lose heat. During the moment of welding, the temperature immediately adjacent to the welding area inside the tank is only around 55°C, and the duration of welding with oil is brief, preventing the oil from igniting. Furthermore, there is no air inside the oil tank, and the oil itself lacks oxygen. Therefore, with proper control, welding repairs with oil present will not lead to combustion.

However, during the repair process, the oil that has already leaked and is currently leaking may not easily combust, but it is highly prone to combustion and decomposition, generating a powerful airflow that makes it difficult for droplets to reach the leakage point. Excessive oil flow may even extinguish the electric arc directly, rendering the repair impossible – a significant challenge in welding repairs. Additionally, the combustion of oil fumes mixed with oil contaminates the leakage point. Even if droplets manage to reach the leakage point by breaking through the airflow, they may struggle to fuse effectively with the metal at the leakage point, impacting the density of the weld and resulting in multiple leakages. Lastly, the intense convective heat transfer within the oil tank prevents the temperature of the tank walls from rising, causing the leaked oil to decompose rapidly and the droplets to cool quickly, reducing their fusion capability.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

Know more about power transformer and reactor:www.lstransformer.com