Cartridge filters constructed cartridges

FIGURE 5.19 The H-filter cartridge was constructed on a polyester chip for blood cell removal. The inset illustrates the diffusive mass transfer. First, to prime the device (1) the pneumetic valve V2 was closed and blood sample placed in PI was pumped (via SI) to fill SL up to V2, and the receiver solution placed in P2 was pumped (via S2) to fill RL up to HI. (2) Then V2 is opened (VI is closed), the blood sample was pumped to reach HI (the start of the H-filter, see inset), and receiver solution was pumped from HI to H2, and the waste loop (WL) was back-filled (via S3) to H2. Second, to start the process of solution flow and diffusive mass transfer, solution pushing (via SI and S2) and pulling (via S3) was carried out. The products went to PR and blood cells (which diffused to a less extent) went straight to WL [596]. Reprinted with permission from Elsevier Science. 

Disposable cartridge filters should be made of synthetic, non-degradable materials such as nylon or polypropylene. Their construction can be spun-bonded or melt-blown, string-wound, and pleated. These are described below. 

Pleated These cartridge filters are typically used in higher-purity applications, such as pharmaceutical and microelectronics. The filters can have a multi-layered construction or be single layer. Typical materials of construction include polypropylene, polyethersulfone, and borosilicate glass fiber. 

Fig. 3 Construction of pleated membranes for cartridge filters. (Courtesy of the Pall Company, Glen Cove, New York.)...

Flexibility. Cartridge filters are flexible cartridges of different ratings and materials of construction can be interchanged, permitting... 

Cartridge filters are used widely throu out process industries in the clarification of liquids. The media used include yams, papers, felts, binder-fi ee and resin-bonded fibres, synthetic fibres, woven wire, sintered metal powders and fibres, ceramics, etc. The inclusion of membraneous materials. Chapter 10, in cartridge constructions has extended the range of application of these ubiquitous dements so that partides firom approximate 500 pm down to 0.1 pm are separated. 

The second stage of separation offers several alternatives thick media pressure filter, pleated paper roll filter or cartridge, strainer, or hydrocyclone. Only the last, the hydrocyclone, does not reqnire preventative maintenance or utilize consumables, and so seems the best choice, especially from the point of view of flexibility. The hydrocyclone is also extremely durable, due to the abrasive resistant nature of the normal material of construction, namely polyurethane, together with its high impact resistance, frequently necessary in a workshop environment. 

Various materials are used for disposable oil filter elements paper, felt, bulk fibre, wound yam and spun bonds. The impregnated paper element, of pleated form, is still one of the most popular types, as this can provide a cut-off of the required order and also has the necessary strength to withstand the differential pressures that may be involved. This element is arranged annularly in a circular can with perforated inner and outer tubes to produce the cartridge. Similar construction applies in the case of a replaceable unit where the cartridge is permanently fixed inside the outer casing. 

Membrane cartridge filters are extremely flexible and high in tensile strength. The cartridge construction is based on a multi-layer combination of filter media in pleated format. Those polymers that have been used extensively as filtration media in coarser grades are now widely used as membrane filters. A typical format has a cartridge fabricated from a pleated filter pack, which contains a very fine polyolefin fibre prefilter layer, two nylon membranes of the same pore (0.2 pm) size, and a downstream polypropylene support. The layers of nylon microporous membrane and polypropylene prefilter are pleated together and snpported by an inner snpport core. The end-caps and core are melt sealed in polypropylene. 

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