Methods for filing tubes having inner and outer tubes separated by a predetermined gap are provided including delivering the tube to a tube filling station, filling the predetermined gap at the tube filling station by centering the outer tube with respect to an elongated nozzle including a plurality of filling pipes corresponding to the predetermined gap and a mandrel for insertion into the inner tube by means of a centering sleeve disposed externally around the elongated nozzle to provide the outer tube with a nominal cross sectional shape and centering the inner tube with respect to the elongated nozzle by means of the mandrel disposed within the inner tube to provide the inner tube with its nominal cross sectional shape, positioning the elongated nozzle proximate to a common tube shoulder at the first end of the tube connecting the inner tube to the outer tube, filling the predetermined gap with the plurality of filling tubes while guiding the elongated nozzle out of the second end of the tube while retaining the centering sleeve around the elongated nozzle and filling the inner tube. Apparatus for carrying out this method is also disclosed.