Process inefficiencies and unexpected downtime are common enemies of paper, board and tissue producers. Troubleshooting such issues and mitigating their impact on production can be a challenge for many operations, maintenance and engineering personnel in the mill. With thousands of installations supporting paper machines all over the world, under-the-machine pulpers are often overlooked in the stock preparation area due to their long equipment life.
As the OEM experts for legacy Valmet, Metso, Beloit, and Tampella pulpers, here are five important signs that the under-the-machine pulper might be negatively impacting production:
There are a variety of reasons why a pulper may struggle to handle the machine production. Common reasons include poor circulation, hydraulic restrictions and poor retention time. Circulation issues can often be corrected with a pulper rotor upgrade. Hydraulic limitations can often be improved by increasing the open area of the extraction grate. A good first step is to contact an expert to discuss the issues. Valmet can offer audit and inspection services to provide recommendations and plan the right path forward.
It is not uncommon for mills to use under-the-machine pulpers to process other forms of broke such as slabs, split rolls or winder trim. Broke slabs can be especially difficult to process, thereby increasing the potential for wear on the pulper rotor. Depending on a mill's plans for broke processing, Valmet can work with operators and planners to upgrade its rotor based upon their specific pulper operations and controls. In some cases, it is the motor power that limits broke processing.
Excess wear often results in decreased pulper efficiency. Wear is most identified in pulper rotors and extraction grates and can have a negative impact on sheet submergence and proper defibering. As your OEM partner for pulper services, Valmet can inspect your pulper to assess key wear factors such as clearance measurements and reductions in vane height. Also, the operation of shower pipes, vat shape, and lack of stock showers impact the sheet submerge, which are inspection points as well.
As targets change, the production rate on a paper machine may also change. When the production rate increases, retention time decreases. When this occurs, Valmet recommends evaluating discharge pump capacity and the flow of dilution water.
In response to market demand, mills often find it necessary to change the grade of paper they are producing. A change in paper grade often requires an increase in specific energy, which results in a need for additional power. To optimize operations with additional power / energy, it may be necessary to increase pulper speed or upgrade to a more aggressive impeller. Valmet has the expertise and solutions to help you understand the specific process conditions required, the impacts on energy consumption, and how decisions may impact the mill's sustainability goals.
For more assistance optimizing your stock prep operations, contact your Valmet representative.