—————Key path of choosing the appropriate E.M.I Vibrator :—————-
—–BULK MATERIAL IN MOTION:—–
Vibration technology is used in most diverse application technological areas. In the “circuit of bulk materials” vibrators are used most beneficially for screening, filling, transporting, emptying and conveying.
They are used for both the improvement of processes as well as for the solution of problems, if the “circuit” should come to a halt.
Within the circuit there are tasks and problems, which can be solved with the help of vibration technology
1. Screening of bulk materials
Screens separate bulk materials according to size or retain contaminants. Directed oscillation movements help to move the product over the screen and keep the screen meshes free at the same time.
2. Filling of bulk materials into containers or Big Bags
As much product as possible should be filled by weight into a container. Pouring cones during filling and air voids inside the product are most annoying. The assistance of vibration should help to fill containers optimally.
3 a. Transport of bulk materials in containers or Big Bags.
No transport process can be accomplished without vibration. This is why products in drumsare compacted during transport with a truck. Due to the content being
3 a. Transport of bulk materials in containers or Big Bags.
No transport process can be accomplished without vibration. This is why products in drumsare compacted during transport with a truck. Due to the content being compacted it cannot be easily poured out of the container or Big Bags.
3 b. Emptying such containers.
Due to the compaction the product rests against the slanted wall surfaces. This causes the formation of bridges. The outflow is restricted. Vibration should now destruct these bridges and at the same time clear the walls from product deposits.
4. Conveying of bulk materials
When emptying the containers or for further processing bulk materials must be conveyed. During such processes distances of various lengths must be covered with various conveying speeds. Vibration movements should help to push the material in “throwing direction”.
For each of the above mentioned tasks there is the correct vibrator available. For better understanding these can be divided according to their vibration characteristics:
The drive of discharge, conveying and screening troughs requires directed oscillations, the effective direction of which is determined by the inclination of the vibrator with respect to the bottom of the through. Inclinations of 30 to 45° are quite common in this respect. The material to be conveyed is pushed under this angle and moves on in form of a throwing parable. For screening the attack angle is steeper, so that the product falls almost vertically on the screening floor.
The conveying speed is influenced by the throwing angle. However, it also depends on the amplitude and the frequency. If higher conveying performances are required one chooses higher amplitudes with lower frequencies. This allows for the avoidance of resonance oscillations and oscillation nodes, particularly on light weight constructions. Light conveyor troughs therefore enable higher amplitudes and thereby higher conveying performance.
Movement of the trough is achieved by the oscillation of the trough against the moving mass of the vibrator.
The movements are there by divided in relation to their masses.
—————Center of gravity trough and position of vibrator—————-
When mounting the trough on pressure springs the direction of force of the vibrator mounted in throwing direction must pass through the centre of gravity of the trough. Only in this case all points of the trough are uniformly lifted in throwing direction. The installation on leaf springs does not cause any problems at all.
Due to the shape of these elements, which permit only one direction of movement, the trough is uniformly lifted in throwing direction at any bearing point. The throwing angle is thereby determined by the leaf springs. The position of the vibrator is only of secondary importance
When choosing silos for the storage of bulk materials very often only data such as storage capacity, storage contents and material properties are taken into account during the planning process.
There is mostly a lack of knowledge about the flowing behavior. This frequently causes interruptions in the material flow. If the discharge opening is clogged workers use sledge hammers to free it again. Such ”cosmetic measures” can be found in many production plants.
The type of material flow can be divided into two different main groups:
1. Mass flow.
2. Core flow.
The occurring type of flow depends on the friction/adhesion of the bulk material on the wall of the silo and on the shape of the discharge funnel.
The flow is called mass flow, if the complete stored bulk material starts to move when emptying the silo. In a core flow silo, however, the bulk material flows through a flow tube, whereby product permanently slips from the surface into this tube. A dead zone without movement of material forms around the flow tube. This dead zone will never be cleared if it is not completely emptied before filling. The storage time will be extended over an undefined period of time, which will impair the quality of the end products, especially in case of perishable goods.
In many cases these quality reductions are never viewed in relation with the core flow silo.
Vibrators mounted to the outside wall will solve the problem. Moving the slanted wall by vibration will reduce the friction between the material components and overcome the adhesive forces between silo wall and bulk material. The material bridge will collapse and the bulk material will flow out.
Outside vibrators with a frequency of 3000 oscillations per minute deliver good results if they excite only the wall and do not shake the whole container
—————–INSTALLING RIGHT VIBRATOR AT RIGHT PLACE:——————-
Elastic products, which become liquid under the influence of vibrations at higher acceleration (Tixothopy –milk products to synthetic moldings sand): Compressed air operated turbine vibrators.
These vibrators produce rotatory vibrations. By using two equal vibrators rotating oppositely, directional vibrations are produced.