TAPPI TIP 0404-07: 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

• Siphon design

• Use of dryer bars

• Pocket ventilation

• Dryer fabric application

• Dryer configuration

•Dryer felting

•Dryer surface scale

• Hood humidity

• Reel moisture content

• Type of pressing

• Amount of pressing

• Breaker stack

Dryers

Drying

Computation

Water removal

Corrugating medium

Linerboard

Wood free papers

Free sheet

Printing papers

Writing papers

Fine papers

Bleached board

Newsprint

Kraft papers

Bags

Mechanical papers

After dryers

Pulps