Backplated paddle impellers
These are shown diagrammatically in Figure 1.68.
Figure 1.67 Open paddle fan — typical characteristic curves
Where the solids are fibrous in character, e. g. wool, paper, or wood shavings, there is tendency for them to wrap round the shaft of an open paddle and clog the unit. The backplate obviates this possibility. All characteristics are generally as the open paddle, except that the backplate paddle need to run about 3% faster taking approximately 6% more power for duties in its optimum range.
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