Pulp & Paper Basis Weight Control Solutions

Basis Weight

Basis weight control is critical to the operation of pulp and paper machines.

The basis weight control valve must be able to respond to small input changes of <1%. In the vast majority of applications, this requirement is met with either a pulsed input gear motor or a stepper motor actuator. The problem is maintenance of these specialized actuators; high-cost, dedicated spares are required. Typically there is a lack of in-house expertise to service these actuators, resulting in production downtime and the need to troubleshoot basis weight valve issues.

Choose a trusted solution.

The Emerson Fisher™ Vee-Ball™, Fisher™ 2052 Diaphragm Rotary Actuator, and Fisher™ FIELDVUE™ DVC6200 Digital Valve Controller have the performance capability required for basis weight control with proven results. The solution utilizes standard Fisher products used on many applications in a pulp mill, resulting in reduced maintenance costs and an eliminated need for dedicated spare parts. Production downtime is reduced as in-house knowledge/expertise to troubleshoot and repair is readily available.

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Pulp Machine Control

Effective operation of the pulp machine can be extremely difficult.

The basis weight and moisture content are very sensitive to small changes in the feed system and are tightly coupled. Production rate changes must be based on very accurately timed changes in thick stock flow, speed, and dryer pressure to avoid upsets. Upset conditions can easily cause a sheet break resulting in lost production.

Implement our proven machine control strategy.

Our machine control strategy stabilizes the sheet machine direction basis weight and air dry content by employing a model-based, multivariable control strategy. The model is based on machine speed, thick stock flow, headbox pressure or level, and dryer pressure and can easily be extended to include disturbances such as broke addition.

Features:

Maximizing production is inherently included, so that the system will automatically default to air dry control over basis weight control if the process is dryer limited
Fully automated production ramping is included
Disturbance rejection is a key part of the system
Intelligent use of scanner data is built into the system
Flexible use of instrumentation is part of the design
Model deadtime varies based on the production rate, so that as the machine slows down, the feedback slows
Model predictive and expert system logic for decision-making provides flexibility and the ability to respond effectively to the widest possible variety of real-time conditions