Screening machines for the production of a variety of sand granulations

The applications for sand are almost unlimited: whether in the production of ceramics, in glass fibers, in the chemical industry, as abrasives and separating materials, as foundry sand or in the construction industry. Each of these applications has a specific composition of various chemical and/or natural components that must be precisely maintained. The high accuracy of RHEWUM screening machines can handle any application.

The world's sands are becoming scarce. This is a major challenge for the construction industry in particular. Most buildings are made of concrete, which itself consists of 60 percent sand. As sand is a natural product, the properties of sand sometimes vary greatly and thus the demands on the screening machine are very high. Sand for the production of concrete is subject to relevant standards. They usually have a grain size between 0 and 2 mm, while gravel or chippings range from 2 to 8 mm.

Perfect classification of sand

The RHEflex^® linear vibrating screen is a robust screening machine for medium and coarser separations at approx. 2 to 10 mm. It is tolerant to material fluctuations and requires minimal maintenance. The screen mesh can be changed in just a few minutes. The two sturdy unbalance motors are located outside the machine and are therefore easily accessible for adjustments or repairs.

Perfect for sand classification in the fine to medium grain range as well as for naturally moist sands, however, is the directly excited vibratory sieve RHEmoto^®, driven by numerous small unbalanced motors. This machine offers the advantage of extremely high accelerations of the screen mesh. These are achieved by small masses that have to be accelerated. Instead of setting the entire machine body in motion, as is the case with linear vibrating screens, the machine housing remains static in this type of construction. This offers advantages in the separation of demanding materials in terms of particle size as well as keeping the screen cloths free. Automatic, adjustable cleaning cycles of the screen cloths additionally reduce clogging and avoid costly production downtimes.

With the same advantages but even higher, exorbitant accelerations at the screen mesh, the vibrating screen RHEsono^® creates even more precise and finer separations down to 100 µm by using drives from electromagnets instead of unbalanced motors.

As an optimal solution, a combination of the two techniques can be combined in only one machine: the RHEfino. The coarser separation takes place in the feeder using vibrating bar grates. The medium-sized separations are realized by directly excited screen decks with unbalanced motors, a simple and cost-effective alternative to electromagnetic drives. Critical cuts of less than 2 mm are made using the electromagnet drive. A design with up to 5 screening machine decks can be realized without any problems.

Semi-stationary sand preparation with screening machines

The utilization of sand as a resource is usually operated in stationary systems. The sand is washed for this purpose and classified into appropriate grain classes. If the resource sand is not available, gravels can alternatively be crushed and subsequently classified. This can be done in a semi-stationary processing as well. The so called manufactured sand (M-Sand) has many advantages which makes it the best sand suitable for construction. RHEWUM is able to design semi-stationary sand preparation plants with first-class screening machines such as the RHEflex^® linear vibrating screen as well as the RHEfino vibrating screen and produce sands directly on site in the quarry without having to transport them over long distances before processing.

Semi-stationary means that the required sand is produced in a light steel construction. This is only possible by the advantageous arrangement of the required machines. While the presumably heavy crusher is positioned close to the bottom, directly excited static screening machines are used for the subsequent fine screening. This significantly relieves the steel structure and the plant can be easily relocated at a later date.