The cylindrical filter surface of a drum filter is increased in effective area by providing radial inward and outward undulations in the general cylindrical shape instead of the cylindrical surface of the prior art.
In order to create a rotating drum filter with a filter medium that is extremely fine-meshed and nonetheless has a long service life, whereby the filter medium need not be completely replaced given localized damage thereto, it is inventively proposed that the filter medium be formed of a composite element body with at least two metallic layers, namely with an extremely finely porous, outer metal layer or, respectively, stainless steel fabric that is firmly applied onto at least one metallic supporting grid layer or, respectively, onto a stainless steel fabric layer that is coarse-meshed compared thereto.
A vacuum drum washer is designed to enable the use of an end-draining drum for drum lengths exceeding 20 feet. The drum washer includes a cylindrical drum having a mesh screen defining an exterior wall. A plurality of outer filtrate channels are disposed radially inward from the mesh screen. A plurality of inner filtrate channels are disposed radially inward from the outer filtrate channels and extend along generally less than an entire length of the drum. A transfer channel connects the outer filtrate channels and the inner filtrate channels. A plurality of radial drainage chutes are disposed adjacent a head end of the outer and inner filtrate channels, which direct the filtrate to a drain valve.
A vacuum drum washer is designed to enable the use of an end-draining drum for drum lengths exceeding 20 feet. The drum washer includes a cylindrical drum having a mesh screen defining an exterior wall. A plurality of outer filtrate channels are disposed radially inward from the mesh screen. A plurality of inner filtrate channels are disposed radially inward from the outer filtrate channels and extend along generally less than an entire length of the drum. A transfer channel connects the outer filtrate channels and the inner filtrate channels. A plurality of radial drainage chutes are disposed adjacent a head end of the outer and inner filtrate channels, which direct the filtrate to a drain valve.
An extended-area filter for filtering plastic stock at high pressures has a breaker plate with an undulating surface confronting the oncoming stock which substantially doubles the available filter area. Screen packs having fixed therein the same surface configuration are supported uniformly on the undulating surface against collapse under the operating pressure.
