Last week I railed about open-to-the atmosphere forming sections. This week, I shall rant about press sections.
Let's start with save-all pans. These things encompass about as much technology as a bed pan.
First, they depend on gravity. Clue-if you are depending on gravity you do not have a controlled process, unless you are operating a hydroelectric plant, which is still subject to rainfall. Seen a recent photograph of Lake Mead? If the press section were enclosed and pressurized, one could make water go where one wants it to go.
Uhle boxes are the other example of leaving conditions to luck in the press section. The ability of a uhle box to pull water out of the fabric is dependent to some degree on the quality of air sucked through the uhle box. If hot, dry air were available on the intake side of a uhle box, imagine how efficient they could be. Imagine how little wear they could impart to the fabric. Perhaps they could even be "zoned' to take more water out in certain zones than in others, hence imparting a new element of control to the paper making process.
The uhle box is an underappreciated potential control tool in the papermaking process.
In my lifetime we have gone from painted press sections to stainless-clad press sections to all stainless press sections. These evolutions were driven by material costs, not scientific process design. Let's build a press section scientifically and see what it looks like.
Start with a clean piece of paper, or these days, a blank computer screen and design a press section that does not incorporate centuries of bad habits.
