Horizontal plate filters are commonly used for various industrial application for filtering different types of liquids, such as coolants for machines. A typical filter for this use is disclosed in U.S. Pat. No. 4,065,390.
Filters of the horizontal plate type have been considered for use in filtering liquids which comprise foods, pharmaceutical preparations and other substances containing bacteria; however, conventional horizontal plate filters are designed and constructed in a manner such that it is extremely difficult or practically impossible to adequately clean the parts of the filter plates of the filter to meet sanitation requirements and to prevent contamination of filtrate passing through the plates. Specifically, filter plates of this type of filter generally have fixed manifolds interiorly of the plates. These manifolds have inner surfaces which cannot be properly reached by a cleaning solution, such as a high pressure jet of hot water or steam. Moreover, such manifolds do not have the quality of finish that is required for food or pharmaceutical grade service. Also, crevices are formed interiorly of the manifolds when the manifolds are welded to the adjacent walls, and these crevices collect filtered matter and are virtually impossible to clean properly, thus promoting bacterial and fungal growth in the manifolds. The crevices will also concentrate mildly corrosive substances and promote the phenomenon commonly called crevice corrison which leads to rapid weld failure and the inclusion of corrosion products in the filtrate.
Because of the foregoing drawbacks of conventional filters of the horizontal plate type, a need has arisen for an improved filter plate for such a filter so that the filter can be used for food and pharmaceutical grade service.