| 摘要 |
An insulated tank construction for a water heater, including a cylindrical tank, a cylindrical shell placed around and spaced radially apart from the tank to form an annular space, and a ring-shaped form dam disposed circumferentially at a selected position in the annular space along the height of the tank. The foam dam is comprised of a resilient compressible material, preferably porous, open-cell polyurethane foam, and has an inner diameter less than the tank outer diameter and an outer diameter greater than the shell inner diameter. Thus, the foam dam is compressed into sealing engagement with both the tank wall and the shell wall. The shell inner wall, foam dam and tank outer wall form an annular chamber within the annular space. Expandable polymer foam material is injected into the annular chamber and expanded to form a jacket of insulating foam around the tank. Initially, gasses generated by expansion of the foam escape the annular chamber through the porous body of the foam dam. However, the fluid polymer foam will not flow through the porous body and the foam dam retains the foaming polymer within the annular chamber. For gas fired water heaters, which have a hot heating chamber at the bottom, the foam dam will prevent flammable polymer foam from contacting the heating chamber.
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