Editing Paper machine (section)

=== Dryer section ===

[[File:Papermaking machine at a paper mill near Pensacola.jpg|thumb|right|300px| Dryer section of an older Fourdrinier-style paper-making machine. These narrow, small diameter dryers are not enclosed by a hood, dating the photo to before the 1970s.]]
The dryer section of the paper machine, as its name suggests, dries the paper by way of a series of internally [[steam]]-heated cylinders that evaporate the moisture. Steam pressures may range up to 160 psig. Steam enters the end of the dryer head (cylinder cap) through a steam joint and condensate exits through a siphon that goes from the internal shell to a centre pipe.  From the centre pipe the condensate exits through a joint on the dryer head.  Wide machines require multiple siphons.  In faster machines, centrifugal force holds the condensate layer still against the shell and turbulence generating bars are typically used to agitate the condensate layer and improve heat transfer.<ref name="Technical Association for the Pulp and Paper Industry" />

The sheet is usually held against the dryers by long felt loops on the top and bottom of each dryer section.  The felts greatly improve heat transfer.  Dryer felts are made of coarse thread and have a very open weave that is almost see through,  It is common to have the first bottom dryer section unfelted to dump broke on the basement floor during sheet breaks or when threading the sheet.

Paper dryers are typically arranged in groups called ''sections''  so that they can be run at a progressively slightly slower speed to compensate for sheet shrinkage as the paper dries. Some grades of paper may also stretch as they run through the machine, requiring increasing speed between sections.  The gaps between sections are called ''draws''.

The drying sections are usually enclosed to conserve heat.  Heated air is usually supplied to the pockets where the sheet breaks contact with the driers.  This increases the rate of drying. The pocket ventilating tubes have slots along their entire length that face into the pocket.  The dryer hoods are usually exhausted with a series of roof mounted hood exhausts fans down the dryer section.