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Roll compaction - process basis of dry granulation

May 11th 2015 at 6:13 AM

Different dry granulation methods-

Dry granulation can be done using two different methods, slugging and roll compaction. The process of obtaining the compacts is done by slugging and roller compaction.

Roll compaction-

A Roll compactor machine is used for dry granulation method. The two counter rotating rollers press, the fine powders to form into solid compacts or sheets which are called flakes or chips.

What happens inside?

With the use of a comminuting mill or oscillatory Granulator machine the flakes or chips are reduced to the desired grain size. The size of the grain depends on the size of the sieve and hence the sieve must be selected carefully. The screening machine can be used to achieve further dust free grains. The fines which are separated can be recomputed with roll compactor machine.

The process of compaction involves feeding of crystalline powder into the charging hopper of the roll compactor. The vertical feed screw which is hydraulically controlled feed the powder into the compacting zone where the rollers are present through the pre compacting chamber. The speed of the feed screw is adjusted through AC variable frequency drive in such a way that the feed screw pressures the powder right between the gaps of rollers.

The crystalline powder turns out to form chips or flakes from the rollers.

Once proper synchronization of roller speed and feed screw speed is got it can be used to achieve more output for the same machine.

What it is made of?

It is made up of s.s. 316 and the contact parts can be dismantled easily except the rollers. The compact rolls are made of tools steel with electro less nickel plating or hard chrome plating on it.

The design of the model can be made plain, water jacketed and even flameproof.

The Screw is driven through an AC variable frequency drive.

The Safety slipping clutch is used between gear box and feed screw. Twin shaft gear box with drive unit are coupled for steady torque loadings on the rolls. Pre compression chamber is made in such a way that product rolls without any slippage and leakage.

The feed screw has a hydraulic mechanism which can be operated by hand.

Slugging-

The process is coined as slugging when a tablet press is used for the compaction process. This method is not widely used. In fact, slugging is hardly used anywhere as a dry granulation method now. The reason behind this is: the small size particles' cannot flow well into the die of a tablet press. This results in the difference in weights of different tablets.

There are large variations in the amount of force acting on the individual slugs, i.e., tablets which lead to variation in the mechanical strength of slug.


Hence the properties of the granulates of this process cannot be well controlled. Therefore finds limitation of use as the process of dry granulation.

Mills used-

There are different types of mills used in the process of dry granulation. Some of them are comminuting mill, multi mill, fluid bed dryer and tray dryer.

Author Bio:

Katharine Hurley works with Cemach Limited, The India based manufacturer and exporter of pharmaceutical machineries company offers Roll Compactor, Roller compactor, Tablet Press Machine, Tablet Tooling, Rapid Mixer Granulator, Pharmaceutical Machineries etc. For More Details visit the website.

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