Distribution Transformer Manufacturing Tour Part 2     While the cores, coils and the core/coil assemblies are being processed, the tanks are being manufactured. The tanks are rolled from low-carbon steel utilizing a state of the art CNC pyramid roller. Side seam welding is performed automatically by a submerged arc welder. The bottom is recessed and the edge rounded to aid in paint retention and allow easier handling. Each tank is carefully tested to ensure leak free construction.   Upon completion of the tank fabrication, each tank component is cleaned utilizing an automatic steel shot blast equipment and then processed through a multi-stage wash/phosphate coating system. The steel shot blast process cleans the metal and provides an excellent adhesion pattern for the powder paint while the wash/phosphate system provides a thin phosphate coating on the tank surface to enhance rust prevention. The final coat of electrostatically applied powder forms a hard durable finish that withstands the elements. Covers are insulated to reduce outages caused by wildlife.   In the new pole assembly area, the core/coil assembly is mated to a tank which has been preped with ground lugs, and decals. The interior assembly is then completed and all thru tank wall components are affixed and connected. Each transformer is then individually vacuumed (to complete the drying process) and filled with de-gassed high dielectric strength oil. The transformer remains under vacuum while the unit is filled with oil so as to ensure that all of the air and moisture are removed.   Upon complete interior assembly, the cover-retaining band provides even gasket compression plus conforms to ANSI requirements for a venting cover design. High voltage bushings are made of a strong wet process porcelain. The low voltage bushings utilize a polymer housing. Terminals are plated for compatibility with copper and aluminum leads.     Continue with tour