The main goal of a paper or board machine stock system is to consistently supply the desired mixture of fibers, fillers, chemicals, and water to the paper or board making process. As part of this goal, it is important to control two stock variables - pH and consistency. If either of these variables is outside its desired range, the sheet produced will not meet product specifications. Having good control of stock pH and consistency helps to produce the same quality sheet, day in and day out.
Learning Objectives
At the end of this module, you will be able to:
- Identify safety hazards and safety guidelines related to stock systems on paper and board machines, including pH control systems
- Define "consistency," "pH," "acid," "base" and "buffer"
- Identify the benefits of good consistency control
- Identify and describe the types of consistency transmitters
- Describe common consistency control strategies, including feedback, feedforward and cascade
- Describe the pH scale
- Describe pH measurement and control
- Describe the impact of pH on wet end chemistry