Depth filters, pleated elements and other types

What type of filter do I use? What is the most economical solution and does it meet the required quality standards in the long term? To ensure that the type is the right one, Wolftechnik offers a wide range of filter elements for the best quality and economy, such as MS stainless steel mesh cartridges, WFMLP multilayer pleated elements, WFMG depth filter cartridges, WFPBT polyester pleated elements and many more filter types.

A large number of filter elements can be used to separate contaminants from liquids, which differ in terms of filter material, retention rate and dirt holding capacity. Depending on the filter matrix, depth filters, pleated elements, screens or fabrics should be mentioned here. Depth filter cartridges are generally more suitable for clarification than surface filters (pleated elements, screens, fabric) which are more suitable for classification. Screens and fabrics safely retain coarser impurities.
In particular, these surface filters serve as protection for downstream system components such as pumps, measuring probes or nozzles.
The impurities retained on the surface can be removed again. Screens and fabrics only have a low dirt-holding capacity, but can be cleaned or backwashed and thus reused.

Deep structure and pleated structure

For smaller or more complex particles, depth filters and pleated elements with nominal and absolute separation
rates are used. These differ in the material they are made of and in the manufacturing process.
Products made of polypropylene, e.g. the WFMG-MasterGroove depth filter cartridges, are as depth filter elements more likely be used for separating general contamination and gel-like impurities, than pleated elements made of polypropylene such as the WFPPA pleated elements. Due to their large filter surface and the pleated filter material, these in turn are preferably used as surface filters for separating solid particles at low differential pressures. A depth filter is designed to capture dirt not only on the surface, but also in its inner, porous structure. The outer filter layers are coarser, to separate the coarser particles, and the inner filter layers are finer for the finer particles. Depth filters are particularly suitable where there is a wide range of impurities in terms of particle size and the particles can be coll-ected in the different layers according to their size. Depth filter cartridges with nominal collection rates are used as pre-filters or for the removal of general impurities and turbidity. Depth filter cartridges with absolute filtration rates are used for more demanding filtration processes and as safety filters.
Unlike depth filters, pleated elements are pure surface filters. Due to the pore fineness of the filter material, the particles are to be retained on their surface, not in the filter material itself.
The most important feature of a pleated element is the filter surface. This corres-ponds to approximately 10 times the final filter layer of a depth filter. Accordingly, the advantage of a pleated element lies in the better throughput capacity with simultaneous low pressure losses.

Variable like nature

As in nature, there are combinations here that are better suited to certain separation tasks than the individual variants. For example, polypropylene filter elements such as the WFMLP multi-layer pleated elements as combi-filters utilise the depth filtering effect due to the multi-layer structure and the advantages of the pleated elements through the pleating of the filter fabric. Combi filters have a good dirt-holding capacity and a high throughput rate with a very good absolute retention rate.

As variable as the possibilities are for the filter types, they are just as variable for the Wolftechnik filter housings. WTBKF bag-cartridge- filter housings, for example, can be equipped with filter bags and, in the case of increased quality requirements, with standard filter cartridges. The combination housings are made of stainless steel and are produced in two sizes. The WTBKF85 can be equipped either with a size 2 filter bag or with 5 x 30“ filter cartridges code 5. The WTBKF40 can be equipped with a filter bag size 1 or 5 x 20“ filter cartridges code 5.

Stainless steel sieves or LUPUS®-II filter elements can also be used in the innovative filter housing. As with most Wolftechnik filter housings, the cast stainless steel base ensures a compact and space-saving design and increased ease of servicing. In addition, Wolftechnik housings are equipped with the well-proven hinged cover made of cast stainless steel. Another important feature of the housings is that the position, type and size of the inlet and outlet ports are variable and are not manufactured until the order is placed, according to the customer‘s wishes and the requirements at the place of use.

One housing for many filter types

The WS-Sanitary housings from Wolftechnik, which are particularly well suited for applications in the food sector, are also variable. Depending on the product requirements, various depth filters, pleated elements and membrane filter cartridges can be inserted into the cartridge filter housings, which are specially designed for use in sterile and high-purity production lines for filtering out turbidity and for sterilisation.

The housings are made of stainless steel AISI 316L (1.4404) and are highly polished inside and out. The surface roughness (Ra) is < 0.6 μm inside and 0.8 μm outside. The housing closure of the small 01WS sanitary housings is designed with a v-clamp, while the larger 03WS, 05WS and 07WS sanitary housings are equipped with clip bolts and ring nuts. Filter cartridges with bayonet adapters are provided for use.

The bayonet adapter plate can be removed from the 03WS, 05WS and 07WS sanitary housings for better cleaning. The standard series ranges from a filter housing for a single filter cartridge in lengths of 10“, 20“ and 30“ and ends with filter housings for 7 filter cartridges in lengths from 10“ to 30“. Other sizes can be manufactured on request, as well as special connections. The standard connections for inlet and outlet are TriClamp connectors.

For final filtration (clarification), depth filter cartridges type WFMB (filter ratings: 0.5 – 100 μm nominal), type CP (filter ratings: 1 – 350 μm, nominal) or type BM (filter ratings: 1 – 15 μm, absolute) are used. Membrane filter cartridges type WFPES with hydrophilic polyethersulphone membrane and filter finenesses of 0.04 μm to 1.2 μm are used disinfection filters.

Because membrane filter cartridges are of very high quality, pleated cartridge filters type WFPPF (filter finenesses: 0.2 – 20nμm, absolute) or WFMLP (filter finenesses: 0.3 μm – 150 μm) are used as prefilters.