The transformer tank shall be of the upper flange type with reinforced cover, and the transformer tank shall have rectangular shape. The completely assembled tank including radiators, conservators, and associated oil piping shall be fully vacuum proof. The construction shall be of mild steel and shall be of sufficient strength and rigidity to withstand moving, shipping and handling without any de-formation. All seams and joints other than those of such tank covers Which may be jointed to the upper Flange of the tank by welding, shall be welded both inside and outside of the tank to secure strong. Leak proof joints