| http://www.w3.org/ns/prov#value | - The troughs 28 in which the cover flanges are received are partially filled with a granular material, such as sand, or with fibrous ceramic wool, which forms a retarding barrier to the escape of the inert gas with which the space 16 above the molten zinc is filled and maintained slightly above atmospheric pressure to prevent, or at least limit, the entry of air into that space.
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