Reference Manual

17−5
Figure 17-7. Stratified Headbox
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
Figure 17-8. Cylinder Former
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
D Water can be drained in a much shorter
distance.
D The technology is much faster than a
fourdrinier machine.
These twin-wire formers can be broken up into two
types.
Figure 17-9. Gap-Wire Former
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
D Gap Formers — These devices inject the
headbox jet between two converging wires (figure
17-9). Many gap formers have a large forming roll
where the majority of the sheet drainage occurs.
There are also several high vacuum boxes and a
suction couch roll where the two wires eventually
separate and the sheet is taken into the press
section.
Gap formers hold the speed records for single-ply
grades of paper such as newsprint or copy
papers. This technology is also becoming
competitive in the multi-ply paperboard market.