Yankee dryers are very large drying rolls predominantly used in the production of tissue-type paper products.
Considered as parts of paper-making machines, they are critical to an industry which produces about 300 million metric tons of paper each year.
A typical Yankee dryer is a cast-iron cylinder of about 6 m (19.5 ft) outside diameter, 7.75 m (25.5 ft) width, and weighing about 180 t (200 short ton). It is typically heated by 1.1 Mpa (160 psi) steam and operated at 1900 m/min (6200 ft/min) while one or more pressing rolls apply pressure to the paper sheet and dryer felt on the Yankee face. Fuel-fired air impingement drying is typically provided over the Yankee to increase the drying rate and thus the production rate.
A Yankee dryer is an assembly of several large gray cast-iron parts (shell, heads, multi-piece center shaft, and journals). The shell is commonly made to ASME Code Section VIII, Division 2, using SA-278, Class 30, 40, 50, or 60 gray cast-iron material and internally may be of smooth-bore or ribbed construction. Heads, center shafts, and journals are sometimes ductile cast iron or may be fabricated from steel.
