Introduction
In laboratory testing in the pulp and paper industry, pulp degree is a key indicator of fiber processing and directly affects the physical properties of paper. The Schober Pulping Meter and the Canadian Ionometer are two widely used measuring instruments that follow different standard systems. This article will systematically compare and analyze the two from the aspects of principles, standards, measurement methods and application scenarios, aiming to provide a clear technical reference for industry technicians.
Measurement principle
The Schober pulping meter is based on the water filtration speed of a certain volume of thin pulp suspension through a standard screen under certain conditions. The longer the water filtration time, the higher the degree of fiber hydration or fine fibrosis, and the larger the beating degree value (°SR). The instrument mainly complies with international standards such as ISO 5267-1 and corresponding national standards.
The Canadian Ionometer works by measuring the volume of filtrate flowing out of the side flow pipe under specified conditions. The larger the volume of filtrate liquid flowing out, the better the filtration performance of the slurry, and the higher the freeness value (CSF or ml), which means that the degree of pulping is relatively low. Its operation is mainly based on standards such as ISO 5267-2.
Comparison of measurement methods
The core structure of both instruments includes a conical funnel, a screen assembly, and a measurement system, but the specific design parameters and measurement endpoint determinations are very different.
The Schober method measures the time (in seconds) it takes to filter a volume of filtrate (typically 100 ml) and converts it to a °SR value by a formula or comparison table. Its calculation can be expressed as follows: the slurping degree value is positively correlated with the filtrate time.
The Canadian freeness law directly measures the volume of filtrate collected from the side flow pipe in milliliters, which is the freeness value. The process does not involve time conversion and is a direct measure of volume.
Scope of application:
Schober pulping meters are usually more suitable for slurries with a high degree of pulping and slower water filtration, such as the slurry of many cultural papers. The scale range is usually 0°SR to 100°SR, and the numerical resolution is high.
Canadian Ionometers are more commonly used for slurries that filter water quickly and have a lower degree of pulping, such as newsprint or certain high-yield pulps. The measurement range is usually between 0 ml and 900 ml. There is a negative correlation between the measured values of the two instruments, which can be approximately converted by empirical formulas or conversion tables, but the conversion relationship varies from pulp to pulp and is not absolutely linear.
Key differences
| Contrast dimensions | Schober beating meter |
| Measurement object | filtrate time |
| The results show | Shaw degree (°SR) |
| Applicable slurry tendency | Slurry with high pulping degree and slow water filtration |
| Standard examples | ISO 5267-1 |
| Contrast dimensions | Canadian Liberation Meter |
| Measurement object | filtrate volume |
| The results show | Canadian Degree of Freedom (CSF, ml) |
| Applicable slurry tendency | Slurry with low beating degree and fast water filtration |
| Standard examples | ISO 5267-2 |
Conclusion
The Schober Pulp Meter and the Canadian Freedom Meter are two classic methods for evaluating the filtration performance of pulp water, based on different physical measurement principles, suitable for different slurry ranges, and corresponding to different standard systems. In actual production and development, the choice of instrument depends on the specific pulp type, process stage and standards to be followed. Understanding the difference and connection between the two is of great significance for accurately characterizing the characteristics of slurry and controlling the production process. The data obtained by the two methods can be referred to and converted under certain conditions, but their limitations and specificity should be paid attention to.
References
ISO 5267-1: Pulps — Determination of drainability — Part 1: Schopper-Riegler method.
ISO 5267-2: Pulps — Determination of drainability — Part 2: Canadian Standard freeness method.
Pulp and paper analysis and testing (chapters of related professional books).