FABRIC
FILTER       NEWSLETTER   

May 1999
No. 283

Hans Dietrich Consult on Mark ets, Media and Membranes

Since the patent for GoreTex® has elapsed W.L. Gore is no longer the sole provider of expanded PTFE membrane to the filtration industry. Hans Dietrich of Hans Dietrich Consult lists five competitors currently engaged in this market niche: BHA Tetratec, and Menardi in the U.S.A.; Nitto Denko in Japan and Shanghai Da Gong New Materials in Peoples Republic of China. The price of the membrane media is now determined by the competition among these suppliers. W.L. Gore holds to its policy of selling high-quality ready made filter elements, while others in the group may sell the membrane or laminated media separately.

"The hit of the season, says Dietrich, "is a heavy woven glass fiber cloth of about 20-24 oz/yd2 being sold in a width of 60 inches with an air permeability of 50-60 CFM, 0.5 in. W.G. (which is more than on a standard membrane filter media)." Dietrich, a strong proponent of the advantages of three-dimensional filter media, sees advantages in the fluffiness and flexibility of the texturized fibers in the glass cloth base. With an air permeability in the given range, Dietrich can tolerate the membrane acting as a filter while being supported by the filtration effect of the high porosity glass fabric. Dietrich cautions, however that the cages for such media should have a maximum distance of one inch between vertical wires and wires should be non-corrosive and at least 1/8 inch in diameter. These cage specifications would provide sufficient support for the laminated glass fabric and prevent unnecessary flexing and bending of the filter bag during filtration and cleaning cycles.  Precautions should also be taken to avoid premature delamination and misuse in applications with abrasive dusts such as that in cement mills.

Dietrich says that filter media prices in Europe are also under heavy pressure due to overcapacity and inexpensive imports from the Far East. In order to clarify the qualities of filtration media now on the market Hans Dietrich Consult has developed a standardization program. Filter media may be ranked as follows:

      Consultex — Best qualit

      Profitex — High quality, low price

      Robotex — Rock bottom prices, but acceptable quality
      because of quality controls in raw materials and manufacturing
      processes

     Unotex — Inspected and approved imports

      Hybrotex — Hybrid blends of fibers in the felt as well as in the scrim.

Back to Fabric Filter Newsletter No. 283 Table of Contents