June 5, 2012

BHS delivers its 1000th rotary pressure filter

The team for final assembly of filters with the Sales Director for the Filtration Technology division, Jürgen Maurer, in front of the packaged plant. One of the world's largest rotary pressure filters of type RPF X 20

The team for final assembly of filters, and Jürgen Maurer (2nd from right), Sales Director for the Filtration Technology division, in front of the plant packaged ready for transportation. One of the world's largest rotary pressure filters, type RPF X 20, featuring a filter area of 9.0 m².

In May, BHS-Sonthofen delivered its 1000th rotary pressure filter since the establishment of the Filtration Technology division; the filter plant was supplied to an Asian manufacturer of cellulose derivatives. Thanks to decades of continual development, these filters are today rated for operating pressures of up to 7 bar (g) and temperatures of up to 160 °C.

Prior to this, BHS-Sonthofen had already set a new record at the end of 2011 with the delivery of five RPF X 20 rotary pressure filters to a customer in China: in terms of throughput, they are the world's largest rotary pressure filters, capable of filtering a suspension volume of 225 m³ per hour. With the new plants, which have a filter area of 9 m², BHS is the only manufacturer to offer rotary pressure filters with an atmospheric output of this magnitude.

BHS-Sonthofen has been manufacturing this unique filter system since 1954. This patented filter was developed in Munich in the early 1950s by chief engineer Erich Fest sen. and brought to Sonthofen by the inventor’s son, Dr. Erich Fest, where it formed the basis for the new Filtration Division. At that time, the filter was rated for a maximum operating pressure of 3 bar (g) and temperatures of up to 120 °C.

The unique feature of the filters is that filtration and further treatment of the filter cake take place under pressure, whereas the cake is discharged into the atmosphere from the non-pressurized discharge zone. This enables continuous operation without the use of supplementary equipment. This development led to a technological leap in the filtration technology of the day.

Over the years, BHS has continued to develop the rotary pressure filter, including a complete revision at the end of the 1990s. Detailed design calculations, modern design procedures for mechanical systems (FEA) and process engineering (CFD), new manufacturing technologies and innovative materials – especially in the area of sealing – have made it possible to extend the use of these filters to operating pressures of up to 7 bar (g) and temperatures of up to 160 °C. The series is patented under the name of "Rotary filter plant".

The filter plants are mechanically engineered for demanding applications: the systems supplied to the Asian customer mentioned above have a drum diameter of 1.8 m and an active length of 2 m and must therefore withstand high loads. BHS-Sonthofen uses state-of-the-art calculation and production methods. The result is high-tech mechanical engineering: each of the 35 t filter systems incorporates approximately 20 t of stainless steel.

Furthermore, new technologies for the drive system and drum bearings enable low-maintenance operation of these plants.

The current generation of filters is marketed worldwide by BHS-Sonthofen under the product name “Rotary pressure filter” with the type designation RPF, and is available in sizes ranging from P01 (filter area: 0.18 m2) to X 20 (filter area: 8.8 m2). The machines today enjoy worldwide recognition as state-of-the-art products. With these filters, BHS has opened up new, future-oriented fields of application, for example in the production of cellulose derivatives and plastic intermediates, as well as for demanding processes in the beverage industry and for the filtering of starch.

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