Handcleaned Bar Screens

Many bar screens have no mechanical cleaning devices and are cleaned periodically by hand rakes (see Figure 7.14.2). Manually cleaned screens, except those used for emergency, should be placed on a slope of 30° to 45° with the horizontal. This positioning increases screening surface by 40 to 100%, facilitates cleaning, and prevents excessive head loss by clogging. The clear opening between bars should be 1 to 13/4 in, and operators should remove screening as often as necessary (from two to five times a day) to secure free flow in the sewer.

When excessive head loss is expected, an overflow bypass channel equipped with a trash rack (vertical bars set 3 to 4in apart) can be used.

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