Pharmaceutical industry
A sieve or screener is an essential part of every Pharmaceutical and fine chemical production process, particularly as product quality and integrity are so important. The use of a Vibrowest sieve gets rid of oversized contamination to ensure that ingredients and finished products are quality assured during production and before use or dispatch.
At Vibrowest we are continually developing our range of sieving equipment in order to satisfy the new requirements of the pharmaceutical industry. These demands include improving productivity, product quality and safety.
A sieve consists of a housing containing a removable wire mesh of a defined aperture size. This assembly is vibrated by an electric motor so that small particles can pass through the mesh apertures and any particles or contamination that are too big remain on the top. All Vibrowest units used in the pharmaceutical industry are produced with high-quality good manufacturing practice (GMP) design by ensuring accurate separation. Stainless steel mesh is also specified to give excellent product quality.
All Vibrowest pharmaceutical sieves and separators are manufactured using the highest possible quality 304 or 316L grade stainless steel, ensuring metal impurities are reduced to a minimum. The design eliminates gaps, crevices and hidden areas. In addition, our polishing techniques allow us to offer the highest standard mirror polished finish to a documented Ra 0,03 micron. This, combined with easily dismantled parts, ensures all equipment can be easily and thoroughly cleaned. The sieve mesh itself is removable so that its aperture size can be changed according to the powder being processed. Our units use mesh that is securely bonded with adhesive to a frame, which gives a much higher tension in the mesh than older styles, which secured the frame with a clip or screws. Having a consistent and high tension level gives better throughputs and reduces blinding or blocking of the sieve apertures. We use FDA-approved adhesive to bond the sieve mesh to the frame. |  |
Figure 1. Some pharmaceutical powders may be sticky or have irregular shaped particles, which can cause mesh-blinding problems. | Ultrasonic Deblinding System Most powders can be screened quickly and accurately by a standard sieve, however, some pharmaceutical powders may be sticky or have irregular-shaped particles, which can cause mesh-blinding problems (Figure 1). The method of ultrasonically exciting the stainless steel mesh wires of a powder screening machine by high-frequency, low-amplitude vibration to prevent apertures blocking has been used for over 25 years. The ultrasonic frequency is applied to the sieve mesh via an acoustically developed transducer (Figure 3). This breaks down the surface tension, effectively making the stainless steel wires friction free and preventing particles, both slightly greater and smaller than the mesh, from blinding or blocking it. |
| Screen blinding or blocking is a common problem in the sieving of difficult powders on screens with mesh aperture of mm 0,500 and below. It occurs when either one or a combination of particles sits on or in an aperture of the mesh and stay there, or particles adhere to the mesh wires preventing other particles from passing through these openings. This is particularly common with sticky powders or materials that contain a large number of particles of a size similar to that of the apertures of the mesh. |  |
When blocking occurs, the useful screening area is reduced and, therefore, capacity drops.
There are several knock-on benefits of eliminating blinding via an ultrasonic deblinding device:
- sieving capacities improve, which increases productivity;
- manual cleaning is less frequent, because the mesh is kept free from blockage for longer, which reduces the chance of damaging the mesh;
- powders can be sieved using meshes with smaller apertures, which enables even finer-quality products to be produced than previously possible or even to screen powders that could not be sieved.
