dwg AVX-0807 · rev. A · Filtration Failure Database
The belt keeps failing at the seam
The symptom
The belt splits at the seam after several weeks. After a new seam is fitted, the damage returns in the same place while the belt fabric remains intact.
Root causes
- 01 A clipper seam carries tension through a row of hooks. At high belt tension this connection may be insufficient for the load.
- 02 Poor tracking can push the belt against a guide. The edge then takes a shear load and the seam may open from that side.
- 03 Chemical attack may concentrate at the seam. Polymer, cleaning chemicals and hydrolysis can affect the seam wire or loop. The ratio of exposed surface to material contributes to this vulnerability.
- 04 A worn wedge zone or hardened roll can impose an impact load on the seam at every revolution.
- 05 A replacement belt with the same seam specification may fail again if the cause of the previous failure has not been assessed.
Suitable filter media
- Examine the failure pattern before replacement. Even failure across the width may indicate tension. Failure from one edge may relate to tracking. Thinning or brittle seam material may indicate chemical attack.
- Choose the seam for the load case. A spiral seam distributes tension across the width and may be an alternative where a clipper seam repeatedly fails. A clipper seam may suit belts that need frequent removal.
- Correct a machine-related cause during the same shutdown. Without correcting a tracking fault, the new seam may also be damaged quickly.
- Assess the seam material when chemical attack is involved. The belt fabric and seam element can use different polymers.
- Specify belt and seam together using sludge and machine data. Check whether the previous seam construction remains suitable.
Effect on downtime
A seam failure in service can cause an unplanned press shutdown. A planned belt change allows the seam specification to be revised and any machine-related cause to be corrected at the same time.
Prevention
- Record the location and progression of the seam failure. Photographs of the damage help with the next specification.
- Check tracking and wedge-zone rolls at every belt change.
- Keep a spare belt with the corrected seam specification so an unplanned change does not reintroduce the same fault.
- Record belt life by seam type and compare results under comparable operating conditions.