Mini-Encyclopedia of Papermaking Wet-End Chemistry
Part Three: Equipment & Unit Operations

Foils

The function of hydrofoils ("foils" for short) is to aid in removal of water from a wet web in the early stages of dewatering. On a Fourdrinier paper machine the foils are placed under the forming fabric. Their shape is designed to create suction as the foil and wet web pass over the surface. Hydrofoils also create a brief pressure pulse as the fabric passes over the leading edge. The alternating pressure and vacuum of a series of hydrofoils tends to move fibers around in the wet web, slightly improving the drainage and uniformity of the resulting paper. Also, the pulsation tends to change the drainage mechanism from pure filtration to a combination of filtration and thickening. The washing action of hydrofoils tends to remove fiber fines and fillers from the wire side(s) of a paper sheet. Another function of the hydrofoil is to doctor water from the under-side of the forming fabric.

Request from the webmaster: Our goals include brevity and accuracy. Hopefully we have succeeded with the first goal without sacrificing the second. Please let us know right away if you find an error or omission. Also, please indicate points that need a clearer description.


RETURN TO INDEX PAGE OF ENCYCLOPEDIA

Home page Research opportunities Business opportunities Background information Links to wet-end chemistry E-Mail
This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, m_hubbe@ncsu.edu .