Discrepancies in High Yield Pulp Mass Balance Calculations across Multi Ply Board Mills
High yield pulp mass balances fail when mills exclude white water solubles and moisture variation, exposing buyers to chain of custody audit liabilities.
Shear Force Transmitter
Mechanical Slurry Resistance
Continuous monitoring of wood pulp density in stock preparation pipelines requires sensors that interact with the flowing material. An instrument known as a shear force transmitter measures the mechanical resistance of the pulp slurry as it flows past a blade. This drag is proportional to the concentration of fibres in the liquid.
Sensor Design Principle
Active elements of these transmitters extend directly into the stock flow to experience the continuous shear stress of the fibre network. As the pulp consistency rises, the increased fiber-to-fiber interaction generates greater resistance against the sensing blade. The internal transducer of the shear force transmitter converts this torque or strain into a standard milliamp output.
This measurement principle operates best within a consistency range of two to eight percent, where the fibre network is sufficiently developed to exert measurable shear. Below two percent, the fibre network behaves more like a liquid and cannot be measured by this technology.
Operational Flow Boundary
Flow velocity changes within the pulp pipe can introduce measuring errors if the speed falls below or rises above the sensor’s calibrated range. To prevent these errors, a shear force transmitter is often installed in a straight pipe section far from pumps or elbows that generate turbulence. Mechanical wear of the sensing blade from abrasive fillers can also cause the readings to drift over time.
Regular verification against manual oven-dried samples ensures that the mechanical measurement remains aligned with the actual stock consistency.