Drainage Measurement
Hydraulic resistance quantifies the speed at which water separates from a fibre suspension during the sheet forming process. The iso 5267 schopper riegler protocol defines a standardized methodology for determining the degree of refining applied to chemical pulp by measuring this drainage behavior. Mechanical devices perform this test by allowing one liter of diluted pulp to pass through a standardized wire mesh into two distinct outlet chambers.
The overflow from the side orifice provides the numerical value expressed in degrees where higher figures denote a slower drainage rate associated with more highly fibrillated material.
Refining Influence
Internal fibrillation and the generation of fines alter the permeability of the fibre mat as it builds upon the mesh. Increased mechanical energy input during processing results in higher densities and improved bonding potential but slows the movement of water through the developing web. Variations in the stock consistency or the temperature of the fluid require precise adjustments to the calculation to maintain repeatability across different production batches.
Mills monitor these shifts to adjust the power load on disc refiners or to optimize the mix of recycled and virgin fibres for specific paper grades. Consistency in the drainage output remains a priority for maintaining the stability of the wet end during high speed manufacturing.
Operational Boundary
Performance parameters for drying sections and press configurations depend upon the water removal capacity that is established by the initial drainage resistance. Sheets produced from stock with excessive drainage values demand greater energy for moisture removal and potentially restrict the speed of the paper machine. Conversely, stock with insufficient resistance fails to retain filler particles or creates excessive pinholes in the final product.
Every structural property of the board or paper relies upon the physical interaction between the dispersed fibres and the carrier fluid established at the forming stage.
