Rotary drum pre-coat filters are widely used in the Pulp and Paper industry to de-water lime mud before calcining in the Lime Kiln. Holes often form in the filter media over time and can cause equipment damage, process upsets and dead-load accumulation.
Holes in filter media can be caused by several different mechanisms. A common but not well-known one is worn and damaged division strips, sometimes known as caulking grooves or T-strips. Formed from a single piece of steel, these division strips retain filter media support grids and the fabric and require specific dimensions to properly secure the cloth to the drum. Further, division strip channels are isolated from the vacuum applied to the drum surface. Over time holes may develop in the division strips due to erosion, wear or damage, allowing vacuum communication between the channel and drum surface. This increases velocity through the stretched filter media openings, allowing holes to form. Equipment damage begins to occur due the abrasive nature of lime mud. Which can lead to costly repairs, process upsets and extended downtime.