Typical Nutsche Filter Media Have Problems

Nutsche filters are indispensable in pharmaceutical and fine chemical research and development and production operations. The Nutsche’s ability to wash, slurry and dry the filter cake and operate at high pressure or vacuum, provides a versatile service. Most Nutsches also have an agitator or “paddle” for enhanced mixing and to frequently facilitate cake removal. These features, abilities and enhancements often require a rugged filer medium to withstand the harsh dynamic environment.

Some Nutsches use a single layer of fine wire mesh as the filtration medium. The un-sintered mesh is stretched across a frame and locked into place. Stretching of course places both the warp and weft wires in the mesh in tension and the result is a definite change in mean pore size. To reduce valuable product loss, “heels” are kept to a minimum. Often, the agitator (or plow) lower stop limit is set to as low as 6 mm. Many un-sintered single layer meshes have been destroyed by the high shearing & tangential forces caused by the rotating filter cake during mixing as the paddle descended to its lower stop limit.

Sintered metal powder media, while mechanically superior to single layer wire mesh, are unable to be efficiently backwashed due to their tortuous path isotropy and are poor choices for the Nutsche. Thus, the ideal filtration medium should feature:

• A wide range of operating-temperatures & pressures
• Permanent, uniform pore size
• Corrosion Resistance
• Wear Resistance & Mechanical Strength
• Cleanable by Backwashing
• Surface, not Depth, Filtration

Dynapore® Is The Answer

The diffusion-bonded multiple layer construction of Dynapore® offers every advantage. From strength and durability to the cleanability of an engineered surface filtration medium, Dynapore® is the number one choice of most OEM’s. Dynapore® Nutsche filter media are available in type 316L stainless steel and Hastelloy® C-22 in standard 5-layer TWM™ construction and Hi-Flo BWM™ construction. Custom constructions are available on request.

MKI offers complete fabrication services to replace or recondition your existing Nutsche filter plate assemblies. Simply call us to discuss your needs.