On conventional paper and board machines, the energy required to dry the sheet to the desired moisture target at the reel is supplied by a series of rotating steam-heated dryer cylinders or cans that are grouped together into drive sections. Each drive section is equipped with one or two dryer felts to hold the sheet tightly against the heated dryer cans. This improves heat transfer to maximize drying, and also helps control cross-machine direction shrinkage and other sheet distortions. On many machines, dryer felts also drive some of the cans. This course covers the design and construction of dryer felts.
•List the functions of a dryer felt
•Identify appropriate machine locations for single-tier and double-tier felt sections
•List the typical properties desired of a dryer felt
•Differentiate between woven, spiral, and needled dryer fabrics
•Describe the impact of dryer felt permeability and surface roughness on the product and on the drying process
•List common materials of construction for modern dryer fabrics
•Describe the different yarn types used in dryer felts
•Explain why dryer felts are heat set by the manufacturer
•Identify and describe dryer felt edge treatments
•Identify safety hazards and safety guidelines related to dryer felts
