The main spare parts of the dryer section are dry fabrics and felt ropes. Damage and premature removal of dry fabrics are mostly caused by external and operational factors. Common faults include holes, edge cracking, local creasing, fabric wandering, and squeeze breakage. Except for unexpected and unavoidable failures, most of these problems can be prevented by careful and standardized operation.
Holes are mainly caused by local external force exceeding the bearing limit of the dry fabric.Hard foreign objects entering the running fabric (such as screws left unchecked before startup); excessive paper wrapping at local positions during paper breakage without timely detection or shutdown; excessive paper jamming on guide rollers between dryer cylinders and in pocket ventilation devices will all jack and damage the dry fabric, forming holes.
Edge cracking of dry fabrics mostly occurs on the operator side.
Continuous friction between the deflector baffle and the fabric edge causes cracking at the fabric joint seam.
During paper threading, excessive paper strips wrapped into the guide roller on the operator side lead to overstress on the fabric edge and cause cracks.
The fabric edge is already worn; long-time air blowing directly onto the edge with an air pipe will also accelerate edge cracking.
Local creasing is generally caused by excessive paper wrapping inside dryer cylinders during paper breakage. It also occurs when the dry fabric joint is severely misaligned, or when the fabric wanders due to malfunction of the fabric corrector (though found in time, local creases have already formed).
Fabric wandering is usually caused by sudden failure of the corrector baffle or falling off of the air pipe.In addition, during paper breakage and splicing, waste paper strips may hang on the corrector baffle (mainly the lower dry fabric), jamming the corrector and resulting in wandering. During paper threading, especially for long threading time, the dryer operator shall timely clean wrapped paper on the machine frame, corrector and guide rollers.
Squeeze breakage and subsequent removal of dry fabrics are mainly due to severe paper wrapping in dryer cylinders after paper breakage.Once paper breakage occurs, operators shall rush to the site immediately, inspect every dryer cylinder for paper wrapping, and stop the machine for disposal in a timely manner.If paper wrapping happens during paper threading and web spreading after breakage, the operator shall promptly cut off the paper web and stop the corresponding group of dryer cylinders.Besides, excessive paper accumulation in the clamping area between the paper stabilizing box and dry fabric during threading may also squeeze and break the fabric.
After long-term operation, friction between the dry fabric edge and corrector baffle will inevitably cause edge wear. During machine shutdown, edge hot sealing must be performed. This can extend the service life of the dry fabric and reduce paper breakage caused by loose wire shedding and edge deviation.
If the fabric edge is uneven, trim it first with a utility knife. When hot sealing, hold the heater steadily with even force; do not heat one position too long to avoid burning the fabric edge.
