A sealing device generally includes a rotatable support cylinder having an outer, circumferential surface and a heating element disposed about such surface and secured thereto such that the heating element rotates therewith. The heating element is coiled about the outer surface of the cylinder in the form of an overlapping helical pattern. Juxtaposed film plies may be sealed together by bringing the sealing device into rotational contact with the juxtaposed film plies and heating the heating element to a temperature sufficient to cause the film plies to seal together.