Press Section Design

Question 1

What is a laminated press felt?

Answer 1

2 Base weaves joint together by needling

Question 2

What is a nonwoven press felt

Answer 2

The base weaves are not woven. This is really not a common felt as felt life is short. But with a light compressible structure it has good start up

Question 3

What is a hybrid press felt?

Answer 3

It is a combination between woven and non woven felts. It is now the industry standard. So you combine the good start up of nonwovens with the good life of a woven

Question 4

How do you manufacture a press felt?

Answer 4

Warping, spooling, weaving, inspection, heat setting, needling, finishing

Question 5

What does an open felt structure give you vs a denser structure

Answer 5

Open = Low nip dewatering, hydrolyic pressure is lower so it is harder for dewatering
Denser = high nip dewatering as high hydrolyic pressure (contact points)

Question 6

What ‘causes’ dewatering in the press

Answer 6

HYdraulic pressure is needed to create drainage - for this the felt needs to be saturated.
This changes a lot with felt design
Will cause crushing if too wet or rewetting if too coarse

Question 7

What is preferred, high nip dewatering or high uhle dewatering

Answer 7

Nip as it is easier. At uhle box dwell time is very limited so this limits dewatering

Question 8

What can be done to help the start up of a press felt?

Answer 8

Chemicals can be added to increase hydrophilic properties, making it denser (increase hydraulic pressure) and better for start up
Felt edge profiling - edges are made lighter and more open to avoid common edge problems
Special coatings can be added to the surface