Plate construction structural design

Design considerations include the proximity to other metallic structures and existing CP systems, the type of grounding, the estimated remaining service life of the tank, the type and temperature of the stored product, the amount of product stored, the cycling rates, the method of tank bottom plate construction, the type of tank foundation, the type of secondary containment, if any, and the backfill soil characteristics. 

The filter structure consists of a stack of plates attached to a hollow shaft which are mounted inside a pressure vessel with each plate covered with a suitable filter medium. The slurry is fed under pressure into the vessel and the cake, which is retained by the filter medium, forms on the top of each plate whilst the filtrate passes through the hollow shaft further to the process. Filter sizes may vary but generally the maximum is 60 m area and designed for a 6 bar operating pressure. Each circular plate in the stack is constructed with radial ribs that are welded to the bottom and support a horizontal coarse mesh screen which is covered with a finer woven metal screen or filter cloth to retain the cake. The bottom of the plate slopes towards the hollow central shaft which lets the filtrate flow freely through circumferential holes and further down the shaft to the filtrate outlet. The clearance between the plates is maintained by special spacers with "o" rings to positively seal between the slurry that surrounds the plates and the shaft that collects the filtrate. The height of the spacers determine the clearance for cake build-up and may be replaced to meet various process conditions. 

The plate structure must be designed to support the hydraulic loads on the plate during operation, and the loads imposed during construction and maintenance. Typical design values used for these loads are ... 

Planar geometry Although there are variations in detail, the design of the planar or flat plate cell, and how cells are interconnected are essentially as illustrated in Fig. 4.27. The construction may involve a self-supporting, coated electrolyte or, if the operating temperature permits, the anode-electrolyte-cathode structure may be supported on a stainless steel bipolar plate. 

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