The Oil forced Air forced heat exchangers manufactured by Convett are designed for the cooling of the power transformers. The cooling area of the exchangers is an array of finned tubes and it is made by aluminum tubes. The tubes are connected at both ends with the tube sheets. In order to avoid any micro leakage and above all to protect the tube sheets from the corrosion we apply a special resin on the top of the external part of it. The cooling element exchange area is 100% tested at 5.5 bar, it is also equipped with oil headers for oil collecting and guiding to the transformers oil circuit. This oil headers has standard air vent and oil drain plugs as standard but any other specific requirement can be satisfied. The oil headers are mounted to the cooling element with bolts, the oil tightness is guaranteed by a sealing gasket. This mechanical design allows an easier maintenance or cleaning of the cooling element if necessary. The entire cooling element goes through a cleaning process of 8 hours with a specific transformer oil forced system equipped with 20 microns filters. The cooling element is over dimensioned by a minimum of 10% in order to allow the plugging of 1-2 tubes if requested for maintenance.