Fine and very fine screening

Throw screening from the beginning of the 20th century to the present demonstrated by the example of directly excited throw screening machines

Summary: As the screening practice reached the range of fine and very fine classification in the 20th century, also comprising difficult-to-screen materials, such as in ore or salt processing and recycling as well, increased screening forces and screen deck accelerations were required. Thus, the aeration of the material to be screened should be increased and obstructing or clogging of the screen deck be reduced on the one hand, and larger specific throughputs be achieved on the other hand [6]. The technical inventions described in the following for the direct excitation of the screen deck by means of bumper, impactor bar, flip-flop or even ultrasound excitation met the new process requirements to a great extent [9, 11, 12].

1. Throw screening machines directly excited by means of bumpers or impactor bars

The development of bumper-type screens [1], which had begun in America at the beginning of the 20th century, was continued with some efficient new developments mainly in Germany from the middle of the 20th century. These screens were used for mean and fine sizing, in some cases even for very fine sizing. The knowledge acquired in the basic research of special processes proved to be an advantage for this development [2, 3, 13, 14].


The heavily inclined bumper-type screens (the inclination of the screening surface...

Related articles:

Issue 12/2013

The right mesh for screening processes

To ensure safe and efficient screening processes, material, aperture shape, weave, and screening machine must be optimally adapted to the products to be screened. The Haver & Boecker product range...

Issue 12/2009

Further developed

Throw screening from the beginning of the 20th century AD to the present demonstrated by the example of indirectly excited throw screening machines

1 The influence of engineering sciences on the screening practice in the 20th century taking into account demographic facts The scientific-technical revolution, beginning in the 19th and continued in...

Issue 05/2015

Which screen for which application?

Key strengths of JOEST, a medium-sized company and international leader in vibration technology, are its great flexibility, many years of experience in vibration technology as well as its creativity...

Issue 07-08/2017

Screening efficiency - Optimisation of screening performance through process-oriented ­design of screen media

Screening technology is a central part of the raw material preparation and takes on various functions in both mines and quarries from scalping, through protective screening to classification of...

Issue 03/2010


Fine screening machines from Derrick for wet and dry screening in the sand and gravel industry

1 General development Screening of granular materials is as old as mankind. Already early Egyptian drawings show the screening of grain and salt in the dim and distant past. The development of the...