At the end of this module, you will be able to:
- Describe the two types of broke generated on paper and board machines
- List safety hazards and safety guidelines related to broke systems
- Explain why it is important to recover broke for reuse
- Describe the sources of broke to typical under machine repulpers
- Identify the components of a typical under machine repulper
- Explain the importance of consistency and level control in repulper vats
- Explain the importance of broke and dilution white water inventory management
The following key questions are answered in this module:
Why is it important to maintain broke storage chest levels in the 25 to 35% range during normal operations?
This helps ensure sufficient storage capacity during process upsets, such as sheet breaks, threading, and start ups.
Why is broke often thickened so that it can be stored at a higher consistency?
The removal of water on broke thickening equipment increases the storage capacity of the broke chests.
Why is it important to control the level in repulper vats during slushing?
This allows the rotor to effectively circulate and slush the broke, using the least amount of energy and minimizing repulping time.
Why are dry end repulpers typically of heavier construction than other under-machine repulpers?
Dry end repulpers are normally of heavier construction because they must often handle slabs from reels and cull rolls.
Why is it important for the seal pit liquid level to be kept above the dropleg openings from a drum or disc thickener?
To make sure that the dropleg opening is not exposed to air, which would cause the thickener to lose vacuum.
Below is a transcript of the video sample provided for this module:
The broke must be designed to handle full machine production during sheet breaks and threading of the machine. The required storage capacity varies, depending on the amount of broke each machine is capable of generating. Broke chests serve to level out consistency variations and to provide storage. During extended sheet breaks or start-ups, the broke chests will slowly fill up. Once the machine has returned to normal operation, broke chest levels will slowly drop as broke is metered back into the stock system. Broke chests are typically operated in the 25 to 35% level range during normal operations. This helps ensure sufficient storage capacity during process upsets. Broke chest levels must be monitored closely during process upsets to prevent stock from overflowing to the sewer.
Use the additional resources and links below to learn more about this topic: