An independent repair, maintenance, and installation provider used the UL101 during a recent installation of transformers in a substation. Three transformers were being installed. One of the transformers was not able to maintain pressure during the pressure decay test (prior to filling the transformer with oil). Soap & bubbles solution was used to inspect all flanges, gaskets, valves, and weld seams as part of the standard operating procedures. However, no leaks were discovered over a period of four days. The crew had another ultrasound product, which was also incapable of finding the leaks.
The staff was trained on using the UL101, which had been used by other locations to find leaks in transformers. The UL101 discovered several leaks in the transformer with maximum pressure at 7 psia. Further troubleshooting of the transformer by the crew showed there were also internal leaks through valves. The leaks were repaired. The repairs were confirmed by using the UL101 and by repeating the pressure decay test. The transformer is now in operation.