The invention is a sealing mechanism for a steam chest (14) used in the manufacture of textile materials. This invention is a device for heating continuous textile material comprising: a steam chest (14) having a steam inlet, a material inlet (18), and a material outlet (18). A first seal means (16) is located adjacent to the material inlet (18). A second seal means (16) is located adjacent to the material outlet (19). One of the seal means (16) comprising a plurality of expansion chambers (32) located along a curvilinear path.