SIFTERS

PLANSIFTERS

Pillars of a screening :

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Abrasion / friction •
Surface ( % opening / Voltage of the screens ) . •
RPM and eccentricity
The plansifters consist of sieves arranged in a box , are driven by a shaft with a starter motor in eccentric movements , circular .

Is the separation of products from various gauges , animated by stacking sieves a circular motion making the smallest fraction passing through the openings , and the largest fraction rejected . It is therefore of a size classification .

The plansifter receives products from the cylinders , these products are usually transported by pneumatic system , are separated in cyclones ( the product suffers a drop in speed and decant ) , and unloaded by a rotary valve . In plansifter are sorted by difference in particle size and routed according to the diagram grinding .
Types Plansifter

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The drawers are stacked screens in easel planschister but are inserted into side rails , allowing the removal of any single sieve , anywhere without having to remove the sieves that are above it .

However, it has two major drawbacks to the use of this type of plansifter : first loses about 12 % of the area of ​​screening , and can have major problems of product leaks through drawers . •
The overlapping layers sieves and their trays are stacked one over the other . Each stack is secured with a metal frame , and each sieving comprises several cells.

The size of the screens varies according to the type and model of the plansifter , but is usually approximately 150 x 50 cm and depth of 7 to 8 cm .

Although this type of plansifter is very efficient , it has low capacity screening relative to the size of the screen , and to inspect or change a screen requires a lot of space , time and manpower. •
Square sieves sieves are square and of equal size , which makes it to be so interchangeable , are stacked on one another and can be pressed to ensure the tension and prevent leakage of product
The square sifters have high capacity screening because intermediate frames can be used to adjust the height so as to adjust the volume of the cell .
Sieve Types



Long Screeners - (120 cm comp. ) .

Semi - long sieves - ( 80 cm comp. )

Square sieves - ( 50 cm comp. )
Factors influencing the flow in plansifter
All refers to the product:

• Density According to the progress in crushing the specific weight decreases . This feature determines the use of spacers and paragraph . entries in Plansifter . •
Particle size

A product is sieved well as the relationship between the amount of product that enters the plansifter and quantity of extracted product through the screen tends to 1. Closer to 1 for the highest ratio is the flow . •
Particle shape

The product has a rounded shape screening easier . •
moisture

The higher the humidity the more difficult is the grading . Excessively wet wheat considerably reduces the capacity of the mill. •
temperature

The higher temperature is more difficult to sieve
Relative Humidity

The relative humidity in the mill should be low , hence the need for a good vacuum . The higher the relative humidity is more difficult sifting .
Working surface of the sieves .

The actual sifting sieve surface is approximately 85%. The higher this is the largest surface of the sifting plansifter .
feed

The supply must be well distributed to avoid disproportions in screening .

No greater . Entries higher absorption capacity of the product by the plansifter housing.
headroom

The goal is to ensure the free flow time of rejection .

Disruptions - 8 cm Max Headroom on the screen .

Reductions beginning - 4 cm

Final reductions - 3 cm
Chimneys of product output

Should be sufficient for the whole product flow space to avoid congestion in the output.
Speed ​​or time rating

As one increases the rotation of plansifters , decreases the speed of advance of the product because it increases the thickness and length of the above product sieves , increasing the extraction of the product sieves .

Since it can not hold a product on a screen so that it is enough for the desired separation time, it increases the path , that is the number of sieves in order to increase the travel time . Among various ways to vary the speed of classification highlights the change in mesh size , thus slowing or speeding the grading .
Cleaning Screens

There are many cleaning screens systems , each adapting to a kind of sieve. •

• brush

Tapotins ( Cleaners ) - They are fast in operation, simpler and more field action brushes . On the other hand do not clean the bottom of the sieve can be: •

Cotton - always choose a firm plot, not shred , sometimes get impregnated products that increases their resistance . •

Plastic or Rubber - should observe the quality of the material and cleaner format , can wear out too fast or do not clean well screens or even pierce them .