Bag filter housings are often first choice for manufacturers of component cleaning systems when it comes to process design and subsequent system planning. This is not only for economic reasons and due to the high competitive pressure but also in order to achieve the best possible ratio of costs to throughput capacity. However, it is often only apparent during the final acceptance of the system on the customer’s premises whether a system designed in this way will fulfil the operator’s cleanliness requirements. An analysis of residual dirt is the most popular method for this purpose. The number of dirt particles per unit area remaining on the component as well as the maximum size and range of these particles are determined using a standardised procedure.
In the example described here, the residual contamination analysis was negative. Simple filtration using standard bag filters in bag filter housings failed to fulfil the customer’s ongoing production requirements. In the second case study, the existing process filtration with standard bag filters of different finenesses no longer complied with the limit values after the quality assurance requirements for production cleanliness increased. In addition, the service life of the filter bags was unsatisfactory.
Adding further filtration steps to the systems in order to obtain the desired quality was not an option due to the extra space this would entail. To convert the existing system to multistage filtration with additional filter housings, the complete piping system would have had to be converted too, to allow the pump output to be adapted. Removing the bag filter housing and switching over to filter candles despite the high system conversion costs initially seemed to be the most viable solution.
Filter media for better quality
Since both these scenarios are very common, the experts at Wolftechnik – who are in close contact with system manufacturers and end customers and are familiar with their needs – have developed a special range of filter products, including folded filter bags and Lupus II filter elements. The folded bags satisfied both the residual dirt analysis requirements regarding the new component cleaning system and the increased quality specifications for the existing system without having to modify either the system itself or the bag filter housings.
The use of dual-layer WFB-2IP bag filters with internal folding thus simultaneously improves the retention rate in addition to extending the service life. The Lupus II filter elements enable a further quality upgrade. Compared to conventional filter bags, they offer considerably cleaner filtrates and a longer life.
Lupus II filter elements demonstrate the advantages of the depth filter media and folding elements which must be installed in the filter housing for design reasons. They are shipped with a special adapter stick and are optionally designed as folding or multi-layer folding elements. The filter elements can thus be placed into the bag filter housing of any conventional size 1 or 2 type without having to remove the filter basket. The adapter piece securely seals the filter elements in the pressure restrainer baskets without any additional conversion components.
Wolftechnik manufactures all filter types – bags, folding elements, depth filters and Lupus II filter elements – in relevant qualities and from a variety of materials (polypropylene, polyester, nylon, glass fibre). A broad spectrum of applications results, in terms of both the temperature and the composition (watery or containing solvents) of the media to be filtered.
One housing for bags and candles
When even higher quality requirements apply in specific applications or more complex components need to be cleaned, there is no alternative to using Lupus II filter elements in the existing filter housings. In normal operation, however, standard candle filters are far more economical to maintain than special Lupus II products, because they have a larger filter surface overall and a longer service life. System designers and operators should therefore bear this in mind when planning a new system or carrying out extensive modernisation work.
If it is possible that the system will need to fulfil stricter quality requirements at some time in the future, even though it does not need to be operated with filter candles initially, Wolftechnik’s experts recommend allowing for WTBKF bag candle filter housings from the outset. All the filter media described here can be installed in these combined housings. Upgrading from economical bag filters to standard cartridge filters is thus not a problem.
The additional costs compared to retrofitting to a standard candle filter housing are quickly recovered following an upgrade.
Compact and user-friendly
Aside from filtration efficiency, straightforward servicing, too, is an important aspect of any filtration system, for example when changing the filter media. After all, complicated maintenance is not just a question of extra work; it also ties up valuable production capacity and results in more downtime. A cast steel base developed by Wolftechnik ensures that all tank types are built with a compact, space saving design and enables significantly better serviceability.
The housing with the new base is much lower than a set-up with a tripod or three welded feet. The lid aperture is no longer at eye level but rather at chest level or even lower, so that access to the housing for filter changes or maintenance is much easier. Servicing times are shorter and work is generally cleaner and more user-friendly.
Another great advantage of this base comes into play if the discharge has to be guided to the horizontal position again. The 90° arc which is customary on the tripod in the direction of the floor at the lower outlet is now redundant. The floor of the base is arched inwards and the outlet flush with the floor ensures clean residual emptying.
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Author: Peter Krause
Managing Director,
Wolftechnik
