Overview
The pulp pulp degree tester is a key equipment in the field of paper making and pulp testing, which is used to quantitatively evaluate the water filtration performance of pulp, which is the core index to characterize the degree of pulping and the quality of the pulp. The working principle is based on standard conditions, which measures the filtration time or amount of water filtration of a specific volume of slurry suspension through a standard sieve plate, and thus calculates the degree of beating in °SR (Schober degrees). This operation is directly related to the subsequent copying performance of the slurry and the physical properties of the paper, so standardized and accurate operation is crucial.
Instrument structure
The standard grouting degree tester is mainly composed of separation chamber, water filter chamber, screen plate, sealing cone, overflow cylinder and graduated cylinder and other components. The following preparations should be made before operation: ensure that all parts of the instrument are clean and dry, and there are no fibers or impurities residue; Check whether the screen is intact and free of blockage; Confirm that the sealing cone and the water filter chamber are well sealed; Calibrate the temperature and volume measurement unit using a standard thermometer and graduated cylinder; The slurry sample to be tested is prepared and its concentration is diluted and adjusted to a standard temperature, typically 23±1°C.
Operating procedures
The operating procedures can be divided into four main stages: slurry sample preparation, instrument debugging, test execution and result calculation.
Slurry sample preparation
A representative slurry sample was taken and fully relieved to a fiber-free beam in standard relief equipment. Dilute the slurry with distilled or deionized water to the target concentration, typically 0.2% to 0.3% (absolutely dry slurry). The diluted slurry suspension is placed in a constant temperature water bath and stirred continuously to make its temperature uniform and stable at the standard specified temperature. The consistency of temperature has a significant impact on the water filtration rate and must be strictly controlled.
Instrument debugging
Position the instrument horizontally. Raise the sealing cone and wet the screen plate and the wall of the water filter chamber with a small amount of distilled water. Close the drain valve and fill the filter chamber with distilled water at the appropriate standard temperature to check the tightness. Perform a blank water test, which measures the time it takes for 1000 mL of distilled water to pass through the sieve plate at 20±1°C, which should be within the standard range (typically 4.5±0.5 seconds) to verify instrument status.
Test steps
1. Raise the sealing cone and make sure the drain valve is closed.
2. After stirring the prepared standard slurry suspension, quickly take 1000±5mL and pour it into the overflow cylinder.
3. Immediately release the sealing cone so that it falls to close the lower mouth of the water filter chamber and start the stopwatch at the same time. The slurry begins to filter the water through the sieve plate.
4. Observe the leurate flowing into the graduated cylinder. When the elutate reaches 800mL, stop the stopwatch and record the filtration time T (seconds). Some methods also measure the amount of water that continues to flow out after 800mL is filtered out, which is used to calculate the beating degree and water retention value.
The result is calculated
The calculation of the degree of beating (°SR) is based on a standard formula. The most commonly used Schober-Rigler formula is:
SR = (T - t₀) * k
Among them, SR is the degree of beating (°SR), T is the measured water filtration time (seconds), t₀ is the blank water filtration time (seconds), and k is the instrumental constant, which is usually calibrated by standard slurry samples. Each test should be performed at least three parallel assays, taking the arithmetic mean as the final result. The permissible error between parallel measurements must comply with the relevant standards (e.g. ISO 5267-1 or GB/T 3332). If it is an out-of-error, find the cause and retest.
Notes:
During the operation, it should be noted that the slurry sample must be fully relieved and the concentration must be accurate; Temperature control must be precise; The operation action should be fast and coherent to reduce human error; The screen plate needs to be cleaned regularly to prevent eyelets from clogging; The sealing elements should be checked and replaced regularly to ensure tightness. Routine maintenance includes: thorough cleaning of all parts that come into contact with the slurry after each use; avoid hard objects scratching the screen plate; When not used for a long time, the parts should be dried and stored and anti-rust oil should be applied to the metal parts; Regular overall calibration according to national standards or instrument manuals.
FAQs
| phenomenon | Possible causes |
| The results are poorly repeated | Uneven slurry samples, temperature fluctuations, incoherent operation, and poor sealing |
| The measured value is systematically high | The sieve plate is partially blocked, the slurry temperature is low, and the blank time t₀ is large |
| The measured values are systematically low | There is leakage due to poor sealing, high slurry temperature, and small blank time t₀ |
| No water or slow current | The drain valve is not open, the screen plate is seriously blocked, and the slurry concentration is too high |
References
ISO 5267-1: Pulps — Determination of drainability — Part 1: Schopper-Riegler method.
GB/T 3332 Pulp - Determination of pulp degree (Schauber-Rigler method).
TAPPI T 227 om-19: Freeness of pulp (Schopper-Riegler method).
Pulp and Paper Analysis and Testing (3rd Edition), China Light Industry Press.