2786 Chapter 23 



States and one in Canada use the process in which stock is pumped through 

 swinging spouts into a 4- by 8-foot deckle-box positioned on top of an endless 

 screen which also passes between platens of a cold press for dewatering the 

 resultant mat. After the mat is formed on the screen and water drained with 

 vacuum assist, the deckle-box is lifted and the endless screen moves the mat 

 between platens of the dewatering press where mat consistency is increased to 33 

 to 37 percent. On discharge from the dewatering press, mats are delivered by 

 tipple to a multi-opening rack to await charging into a hot press to yield SIS 

 panels. 



Cylinder forming machines. — Cylinder machines are continuous formers, 

 similar in design to the vacuum pulp washer described by figure 23-22 (top). 

 They are simple, relatively inexpensive, rugged, and work well with both 

 hardwoods and softwoods. Single-cylinder machines (fig. 23-31 top) are built 

 in diameters from 8 to 14 feet and are 9 to 15 feet long. The screen-covered 

 cylinder revolves partially submerged in a constant-level vat of continuously 

 agitated stock, where an internal vacuum sucks water through the screen and 

 deposits fibers on it. Forming is complete where the cylinder emerges from the 

 stock vat, and the mat is compressed by press rolls covered with wire or felt to 

 force more water through the mat into the interior of the cylinder. No water is 

 removed from the top (outside) of the mat. A vacuum of 15 to 24 inches of 

 mercury is maintained on the interior portions of the cylinder up to the location 

 where the mat is lifted off the screen by a doctor bar and delivered to a wet press 

 by roller conveyor. A 14-foot-diameter single-cylinder machine can form mats 

 for V^2-insulation board at 50 to 60 feet per minute while rotating 1 . 1 to 1 .4 rpm. 

 Mats for 1-inch insulation board are formed more slowly — about 20 to 24 feet 

 per minute while rotating at 0.45 to 0.55 rpm. Capacity for production of !/2-inch 

 insulation board varies from 70 to 250 tons per day depending on cylinder 

 diameter and length (table 23-5). 



