Applications where sintered screen packs perform more reliably than regular mesh
A particularly useful and commonly demanded filter plate is formed by sandwiching the fine mesh between two layers of medium mesh screens which are then laminated to produce a strong base of multiple layers of square meshes or the earlier 12 X 64 structural support mesh. The initial layer of medium square mesh offers protection to the filter mesh, which in turn offers a suitable pore size. Another layer of square mesh offers internal flow distribution volume and acts as a buffer zone between the filter layer and heavy support layers. Similar to other laminates, this material is used flat or rolled and welded to produce tubular elements. Applications of sintered mesh screens are- polymer filtration, nutsche filter press, pharmaceutical process, gas sparging, beverage filtration and fluidized beds.
The medium to coarse square mesh screens have good mechanical strength, are bonded to coarser meshes for additional mechanical strength where needed. These laminates are ductile and formable and can be considerably deformed into different deep drawn mold shapes. Applications – high pressure and high volume pre-filtration, pulp forming molds for egg boxes, apple trays and molded paper plates and vacuum dryers.
The frame-bounded screenpacks with several layers of square weaves are widely used in polymer production and various other applications in which a fluid flows through the pack. Usually these may be designed with graded density for example a progression of coarser to fine screen sizes inside the pack. When these multiple-layer packs are sintered, the resulting laminate attains a totally different and superior character. The major characteristics of these screens include:
a.      High mechanical strength- Sintered pack attains higher strength and rigidity as compare to regular mesh. It means the pack can withstand higher pressures and throughputs without deflecting. Prevention of migration means more uniform flow across the pack surface without peaking in the center.
b.     Structural integrity- The sintered mesh is fully free from medium movement. There are no loose parts of wire which can other damage the downstream. Sintering prevents separation between the pack layers and lateral flow channels. Residence time of the filtrate decreases and throughput increases. While filtering viscous fluids for example molten polymers, shear is imparted more evenly to the filtrate as the pack remains rigid.
c.      Maintain filtration rating- Wires in regular mesh screens shift and separate when solids operate under high pressure. It results in deformation of mesh. Unlikely, in sintered mesh screens, the wires in each mesh layer are securely bonded together and hence they do not shift even under high pressure. So, the micron rating and bubble point of the mesh remains stable throughout the time and filtration integrity of the pack is not affected.
d.     Cleanability – Sintered mesh screens can withstand several cleaning processes in which other screens usually fail to operate for example high pressure washing, steam cleaning, oven burn-off, furnace firing, caustic bath, passivation baths, solvent cleaning, ultrasonic cleaning and other processes used by expert filter cleaning industries.
Hence the use of sintered mesh screens in heavy filtration applications is found to be more suitable than regular mesh.
