We determine the optimum filter grades, operational parameters, sizes, and designs in close cooperation with our customers.

 

Design/Calculation

Filter elements and filter systems, including housings and system components, are designed to meet the current standards in the individual global regions. These are: the Pressure Equipment Directive 2014/68/EU in the European countries, the Pressure Vessel Design Guide of the American Society of Mechanical Engineers (ASME), and the relevant documents of the AD Codes of Practice
Our calculations are based on the operational parameters provided by our customer, such as the chemical composition and the temperature of the medium to be filtered, the demands on the filter unit, the flow capacity, and the acceptable pressure loss of the filter system. In addition, the space that is available for the filer system is taken into account.

 

Selection of filter media

Filter media are the heart of each filter system, as they determine filtration performance and particle retention. With their specific flow resistances they significantly contribute to the pressure loss and consequently to the energy consumption for filtration and backwashing.
Thus the criteria for selecting the media for a specific process must be: as fine a filter as needed and as much filtrate flux as possible. The selection must be done with the greatest possible care, because it is decisive for process security and operational costs over a long life-time. Besides the main characteristics of particle retention and pressure loss, other properties like mechanical stability under the pressure levels that occur during operation and regeneration must also be considered. Furthermore the processing capabilities, e.g. pleatability, have to be taken into account.
When selecting filter media, we can refer to a large data basis within our company. Otherwise we buy and make up specific filter media according to customer specifications. These are mostly metal media due to their cleanability and durability.
We use metallic nonwovens with filter grades from 2 µm to 80 µm and wire meshes from 5 µm. The nonwovens consist of three-dimensional structures built from laid and sintered fibres. They exhibit high porosity and dust holding capacity, and they can be pleated.
Wire meshes are available with different weaves (square mesh, long mesh, Dutch weave, etc). They are characterized by clearly defined pore sizes, determined by the wire diameters and the weave. They are used as single layers or combined with nonwovens. In some applications the combination of nonwovens from synthetic fibres or glass fibres and metallic wire meshes is also possible.
Due to the customized specification of laminates, the optimum filter fineness and filter performance are achieved for the respective application. This is achieved by connecting two to five layers by a special sinter process, which is carried out by expert manufacturers at our request.
Edge filters are produced as an alternative to nonwovens and meshes for filter grades of 50 µm and higher. The filtration effect is achieved by axially oriented profile bars, around which wires are wound as spirals and welded. The distance between the windings determines the filter fineness.  Edge filters are very robust and easy to clean.

 

Arrangement of filter layers

Optimum filter performance and mechanical stabilities can be achieved through the clever combination of different filter media, which are graded in their fineness. The common design of multilayer filter media comprises one or more filter layers with graded fineness and a support on the filtrate side of the filter. An additional drainage layer is required between the filter medium and support if liquid droplets are to be separated from a gas or air flow.
Multi-layer media can be assembled from different metallic wire meshes as laminates, from wire meshes in combination with metallic nonwovens, and by embedding polymer nonwovens.
Pleating filter media is the treatment of choice for creating a larger filtration area within the same space and thus building up systems that are as compact as possible. Our modern pleating machine enables us to pleat multi-layer media of up to 1.5m wide The challenge in selecting and combining different layers is not only to ensure the required filtration efficiency and stability under operating conditions, but to maintain integrity and stability during the pleating process. This is essential to achieve the required performance and working life of the resulting filter element.