Meta filters are the filters which are used to separate very fine size particles from the liquid or solid suspensions.
It consists of the series of the metal rings which are made of the stain less steel and the drainage grooves.
- Meta filter functions as the strainer (surface filtration) for the separation of the particles.
- In this method metal rings contain semicircular projections which are arranged as a nest to form channels on the edge.
- This channels offers resistance to the flow of solids.
- The clear liquid is collected in to a receiver from the top.
- The construction of meta filters consists of a series of metal rings.
- These are threaded so that a channel is formed on the edges.
- It contains a metal grooved drainage column on which a series of metal rings are packed.
- These rings are usually made of stainless steel and have dimension of about 15 millimeters internal diameter and 22 millimeter external diameter.
- Each metal ring has a number of semi circular projections 0.8 mm in thickness on one side of the surface.
- The projections are arranged the same way up.
- These rings are tightened on the drainage column with a nut.
- Therefore meta filters is also known as edge filters.
Surface view of a ring
Assembly of rings on column
- In the working of the meta filters involves filters are placed in a vessel and may be operated by pumping the slurry under pressure or occasionally by the applications of reduced pressure to the outlet side.
- The slurry passes through the channels formed on the edge between the rings.
- The clear liquid rises up and collected from the outlet into the receiver.
- Meta filter functions as a strainer. For the separation of the fine particles, a bed of suitable materials such as kieseluhr is first built up.
- The pack of the rings serves essentially as a base on which the true filter medium is supported.
- Meta filters are used for the clarification of syrups
- Filtration of the injection solutions
- Clarification of the insulin liquors
- Filtration of the viscous liquids can be achieved by applying pressure.
- Meta filters are used under the high pressure without any danger of bursting the filter medium.
- Running costs are low, as separated filter medium is not used.
- The volume of the residual hold up in the filter is less.
- It can be constructed from the materials that can provide excellent resistance to corrosion and avoid contamination of sensitive products.
- It is very extremely versatile filter.
- It can be used for the filtration of very fine particles using the filter aids.
- Large particles can be separated by building up of a bed of same particles.
- Removal of the cake is carried out very easily by simply back flushing with the water.
- Change over from the batch to another or one product to another is easy.
- Sterile products can be handled.
- C.v.s subrahmanyam et al., pharmaceutical engineering principles and practices-filtration, 2001, page no:268-270.