Wedgewire baskets, introduced to the pulp and paper industry during the late 1980's, have revolutionized pulp screening unit operation. The basis for this success is the increased open area achieved by the uninterrupted slot opening (top to bottom), particularly when compared with conventional milled slotted baskets. This permits the installation of a smaller slot size within a given pressure screen, providing improved quality performance while maintaining or increasing screen capacity.

Significant energy savings can often be achieved by a reduction in the number of screening stages, or elimination of cleaners.

Until 1999, Ashu Engineers purchased its wedgewire baskets from an outside manufacturer. The baskets supplied were produced using the conventional manufacturing method, which mainly consists of pre-assembling a mat of wires and support bars on the flat, then forming the mat to roll to the specified diameter, welding the longitudinal seam, and finally welding the support bars.

The characteristics obtained using that method were not fully satisfactory: poor roundness because of the seam, difference between the target and slot size obtained, variability in the slot size, introduction of high manufacturing stresses, and, significant variation of basket life, especially in severe applications.

Seamless Wedgewire Baskets: Ashu Basket? Baskets
In the meantime, in 1997, the engineers and designers from Ashu Engineers Ltd., Montreal, had decided to do things differently: they started developing a new manufacturing method that would not only allow an increase in the mechanical strength of the baskets, but also provide exceptional dimensional characteristics on every front including slot size, profile, roundness, and concentricity.

The Ashu Basket concept basically consists of assembling the wires directly into the rings using an expandable mandrel. Special reinforced designs (welded or shrunk-on rings, cage, etc.) are no longer required because this method involves no forming. Significantly stronger support rings can be used because there is no limitation on formability. Also, there are no residual stresses due to forming. This combined with optimized welding procedures confer to the Ashu Basket basket superior mechanical strength, unmatched roundness and extremely precise slot width and profile.

The slot width is inspected accurately using laser measurement. The quality control includes measuring the slot width on a complete basket revolution, and providing the user with a detailed report on the actual slot size distribution. This was performed on competitors' baskets to compare results with the Ashu Basket? baskets .

The average slot width of the Ashu Basket? baskets is maintained within 10 µm of the target value with an exceptionally low standard deviation. These values are by far the best offered on the market.

The Ashu Basket basket's low standard deviation in the slot size offers the highest efficiency for a given capacity. Ashu Engineers experts provide assistance to customers in selecting the most appropriate slot size to achieve the desired screening performance and take advantage of the benefits provided by the Ashu Basket? features.

Since introduction of our product in 1998, initially for mechanical pulping applications, more than 30units have been installed. The new basket has demonstrated its superior strength and quality performance. The number of models offered has increased to over 50, to fit the requirements of mills with a variety of screening equipment.

The unmatched performance characteristics of the Ashu Basket baskets are recognized in many sectors of the industry. In the near future this product will be offered to a broader market to satisfy the needs of all pulp and paper manufacturers.

As a final note, the Ashu Basket. Basket story is ongoing and sustained by the valuable efforts of specialists within the organizations. The authors wish to acknowledge the contributions of the many individuals involved in making Ashu Basket a continuing success story.