Paper Machine Drying Rate

This TIP outlines procedures for calculating paper machine drying rates for coated and uncoated papers and provides drying rate curves. The objective of the TIP is to define rate of water removal on a common basis for mills to use to compare a particular machine to past performance and to other machines. The definition of drying rate and its calculation are simple to permit widespread use. These procedures cannot be used for machines with auxiliary drying equipment such as infrared dryers and impingement dryers unless these auxiliary dryers are shut off.

Data points on the curves represent observed performance of existing machines. Lines represent calculated average and two-sigma variation of plotted data.

The calculation does not identify or account for factors that affect drying rate. There are many variables that can affect calculated drying rate. These factors include:

• Sheet furnish
• Dryer configuration
• Type of pressing
• Siphon design
• Dryer felting
• Amount of pressing
• Use of dryer bars
• Dryer surface scale
• Breaker stack
• Pocket ventilation
• Hood humidity
• Dryer fabric application
• Reel moisture content