GB/T 2679.4-1994 Determination of roughness of paper and paperboard (Bendtsen roughness method)
Some standard content:
National Standard of the People's Republic of China
Determination of the roughness of paper and board
(Bendtsen roughness method)
Paper and board-Determination of the roughness(Bendtsen method)
GB/T 2679. 4-- 94
Replaces GB2679.4-81
Part 2:
This standard refers to and adopts the international standard ISO8791.2 "Determination of the roughness/smoothness of paper and board (air leakage method) Bendtsen method".
Subject content and scope of application
This standard specifies the method for determining the roughness of paper and board using a Bendtsen instrument with constant pressure air flow. This standard is applicable to paper and board with a Bendtsen roughness value of approximately 50~1200mL/min, and is not applicable to soft paper, high air permeability paper or uneven paper.
2 Reference standards
GB450 Sampling of paper and paperboard samples
GB10739 Standard atmosphere for handling and testing of pulp, paper and paperboard samples3 Terminology
Bendtsen roughness: The air flow rate between the ring surface of the measuring head and the paper or paperboard under specified conditions and operating pressure, expressed in mL/min.
4 Principle
The sample is in contact with the metal ring surface under a certain pressure, and air with a certain pressure is passed into the ring to measure the air flow rate passing between the sample surface and the metal ring surface. The higher the measured value, the rougher the paper and paperboard. 5 Instruments
5.1 The Bendtsen instrument consists of a compressor, a pressure buffer container, a rotor flowmeter with a pressure regulating valve and a measuring head, as shown in the figure below. The Bendtsen instrument should meet the following requirements, and its maintenance details are shown in Appendix A (Supplement). Approved by the State Administration of Technical Supervision on September 24, 1994 264
Implementation on March 1, 1995
GB/T 2679.4—94
Benter Instrument
A—compressor; B—pressure buffer vessel; C—pressure stabilizing valve; D—central unit; E—measuring head 5.1.1 Measuring head
Mass 267±2g, width of metal measuring ring 0.150±0.002mm, inner diameter 31.5±0.2mm. The measuring head and flow meter are connected by a rubber tube or plastic tube with an inner diameter of 5-6mm and a length not exceeding 600mm. 5.1.2 Flowmeter
10～150mL/min, 50~～500mL/min and some instruments 300~3000mL/min, are required to read accurately to 2mL/min, 5 mL/min and 20 mL/min respectively.wwW.bzxz.Net
5.1.3 Pressure Regulating Valve
The pressure of the gas flow controlled by the pressure regulating valve at the inlet of the flowmeter is 0.74±0.01kPa, 1.47±0.02kPa and 2.20±0.03kPa respectively, of which 1.47kPa is the standard operating pressure. 5.1.4 When using the gas flow pressure of 1.47±0.02kPa and the measuring head of mass 267±2g, the contact pressure of the metal ring on the sample is 98kPa. If a 600g pressure bowl is attached to the measuring head, the contact pressure on the sample is 490kPa. 5.1.5 The flat glass plate
should be sufficiently flat, and the rotor of the flowmeter should not have visible changes within the working area. 5.2 The compressor
should ensure that the air flow pressure before entering the pressure regulator is 127kPa. 5.3 Pressure buffer bottle
about 10L glass bottle.
6 Calibration of the instrument
6.1 The level of the instrument
should be placed in a place without vibration and calibrated to be level. 6.2 Sealing of the instrument
First, place a smooth and soft rubber cloth on the flat glass plate and place the measuring head on it, start the instrument to pass the air flow, and then place the 1.47kPa pressure regulating valve on the shaft to rotate it. The instrument range is connected to the 10~150mL/min flowmeter, and observe whether the rotor of the flowmeter is zero. If it does not rise, it can be dialed to the 50~~500mL/min and 30~~3000mL/min flowmeters. If the indication is zero, it means that the sealing is good. If the rotor rises, it means that there is leakage between the flowmeter and the measuring head. The joints and connecting pipes should be checked. 6.3 Check whether the pressure ring of the measuring head is flat
If the instrument has good sealing, the measuring head can be placed on a clean glass plate, the instrument can be started, the pressure regulating valve can be placed on the shaft, and it can be rotated. The instrument is connected to the low-range flowmeter. At this time, the rotor of the flowmeter should not rise, which is the zero point, indicating that the pressure ring is flat. If it is not at the zero point, the pressure ring can be cleaned with an appropriate solvent (such as carbon tetrachloride) and the pressure ring can be checked with an optical microscope for defects. If a large change is found, a new measuring head should be replaced or manually ground. When grinding, be careful to ensure that the area of the pressure ring is not affected, and then check according to the above method. 6.4 Calibration of the flowmeter
GB/T 2679.4--94
Calibrate with a soap bubble meter or directly with a calibrated capillary (see Appendix B (Supplement)). 7 Preparation and treatment of samples
Cut at least 10 100mm×100mm test pieces from each test surface, mark the front and back sides, and the samples should be flat. The test surface should not have folds, wrinkles, holes, watermarks or other defects, and the test range should not be touched. The samples are treated according to the provisions of GB450 and GB10739, and measured under the temperature and humidity conditions.
8 Test steps
8.1 Start the instrument first, then place the 1.47kPa pressure regulating valve on the shaft, and check the sealing of the instrument and the flatness of the measuring head. 8.2 Place the test piece on the flat glass with the test surface facing up. Turn the ventilation valve, select a flowmeter with a suitable range, and gently place the measuring head on the test piece, keeping the ring surface parallel to the sample surface. Do not apply other pressure to the measuring head, otherwise the measured value will be low. After 5s, read the indication value of the flowmeter rotor, which is the roughness of the test (mL/min). During the measurement, the indicated value should be within the range of 10% to 90% of the flow meter scale value. It is recommended not to use an air flow greater than 1200mL/min. 8.3 After reading the indicated value, measure another test piece. Each test piece can only be measured once (front or back). It is best to use two flow meters for the same sample.
8.4 After the test, take out the pressure regulating valve first, and then turn off the instrument to avoid wear of the pressure regulating valve. 8.5 Determination of compressibility and elasticity
After testing the roughness, add pressure to the measuring head to make the contact pressure 490kPa, read the indicated value of the flow meter, and the percentage of the ratio of this reading to the roughness is expressed as the compressibility of the sample. After removing the pressure, read the indicated value of the flow meter again, and the percentage of the ratio of this reading to the roughness is expressed as the elasticity of the sample. 9 Test report
The test report shall include the following contents:
This standard number;
Test temperature and relative humidity;
Number of tested pieces;
The arithmetic mean of the test results, accurate to three significant figures; If required, the arithmetic mean of the test results of the front and back sides can be reported separately; If the standard pressure is not used, it should be stated in the report; The standard deviation or coefficient of variation of the test results; Abnormalities during the test or operations that are different from this standard. A1 Pressure regulating valve
GB/T 2679.4—94
Appendix A
Maintenance and maintenance of Bentson instrument
(Supplement)
The integrity of the pressure regulating valve should be maintained, and its edges should be avoided from being damaged when the pressure regulating valve is placed. The axial hole of the pressure regulating valve covering the support valve should be kept clean, without oil and dust, and lubricating oil should not be added. First, let the air flow through, then put the pressure regulating valve on the shaft. Before stopping the air flow, take out the pressure regulating valve. A2 Rotor Flowmeter
For newly installed or reinstalled flowmeters after cleaning, carefully check whether the rotor rotates freely. A non-rotating rotor will affect the reading, especially at low flow rates. Check whether there are foreign objects brought into the flowmeter (such as particles from instrument gaskets and connecting pipes), otherwise it will affect the reading. Inspection method: Start the compressor, and after the air flow starts to flow, put 1.The 47kPa pressure regulating valve is gently placed on the shaft so that its rotation direction is consistent with the airflow direction of the axial hole, and the pressure regulating valve can rotate continuously and smoothly. Change the outlet valve of the flowmeter to change the outlet flow, and check whether the rotors of each flowmeter rotate smoothly and whether there are foreign objects entering the flowmeter with the airflow. If the rotor is found to be embedded in the bottom or top spring, when the airflow passes through the pipe and gently taps the instrument, the rotor still cannot rotate freely, you can use a special wrench to disassemble the round nuts at the bottom and top of the flowmeter, remove the metal block at the top, gently take out the glass tube of the flowmeter, remove foreign objects, and use the method of adjusting the shape of the spring to prevent the rotor from being embedded again. The bottom spring should be limited to the concentric hole horizontal to the flowmeter, and the top spring should be limited to the concentric hole vertical to the flowmeter. If the flowmeter tube or rotor is dirty, it will cause the reading to be high. It can be cleaned with carbon tetrachloride and then dried with airflow. If it is washed with liquid detergent (10% aqueous solution), it should be cleaned with distilled water and then dried with airflow. If the flowmeter tube is broken, it should be replaced.
All connecting pipes (rubber or plastic) should be checked regularly for wear and tear, and all pipes should be replaced once a year. A3 Pressure difference check
Use the connector to connect the (water column) pressure gauge and the corresponding capillary to the flow meter outlet. When the air flow rate is as follows, the pressure error should be within 5% of the ideal reading of the pressure gauge.
10~150mL/min rotor flowmeter:
Air flow rate (mL/min)
Ideal reading of pressure gauge (mm)
50~500mL/min rotor flowmeter:
Air flow rate (mL/min)
Ideal reading of pressure gauge (mm)
300~3000mL/min rotor flowmeter:
For air flow rates below 1200mL/min, the ideal reading of the pressure gauge is 150±10mm. To ensure that the test pressure does not drop too significantly, the inner diameter of the tube connecting the measuring head is 5 to 6 mm and the length is not more than 600 mm. 267
B1 Calibration of flowmeter with capillary
GB/T 2679.4-94
Appendix B
Calibration of capillary and flowmeter
(Supplement)
The rotor of the flowmeter is very sensitive to wear. If the scale reading differs from the specified value of the connected capillary by more than 5%, the following steps should be adopted:
B1.1 Calibrate two adjacent flowmeters with capillary. B1.2 If both readings are high, check the cleanliness of the flowmeter and rotor and clean them if necessary. B1.3 If both readings are low, check the blockage of the system, such as folded pipes. B1.4 If the two readings are inconsistent, or B1.2 and B1.3 cannot determine the fault, calibrate the flowmeter with a soap bubble meter or other device at a pressure of 1.47 kPa.
B1.5 If the flowmeter or capillary is judged to be broken from the results of B1.4, it should be replaced. B2 Calibration of rotor flowmeter with soap bubble meter
B2.1 Instruments and materials
B2.1.1 Soap bubble meter
The soap bubble meter (Figure B1) consists of the following parts: a glass bottle with a volume of 1L;
-volume meter (carefully calibrated between two scales), with 100mL, 250mL and 1500mL scales, different scale ranges can be obtained by reliably replacing the volume meter;
-needle valve (control valve).
B2.1.2 Stopwatch.
B2.1.3 Soap solution: 3% to 5% liquid detergent water solution. B2.2 Calibration steps
Remove the measuring head from the hose at the outlet of the flowmeter and connect the hose to the bubble meter A. First, vent the air flow, then place the 1.47kPa pressure regulating valve on the shaft and rotate it. Open the vent valve, and the air flow is directed from the flowmeter to the bubble meter for calibration. Carefully adjust the pipe clamp and the needle valve to make the flow rate of the flowmeter constant. Quickly squeeze the rubber ball at the bottom of the volume meter to allow the soap bubble to enter the volume meter. Measure the time it takes for the soap bubble to pass between the two scales of the calibrated volume, expressed in seconds. The range of the selected volume meter should allow the measurement time to exceed 30s. Repeat the measurement of 6 different air flows and record the atmospheric pressure at that time.
GB/T2679.4—94
Figure B1 Soap meter
A-connection point; B—1L glass bottle; C—needle valve; D—volumeter; E—rubber ball Note: The system can produce calibration errors under high air flow pressure drop. To eliminate this error, the length and diameter of the pipe must be the same as that tested. B2.3 Calculation
Check whether the reading error of the flowmeter is within 5%. If not, a correction diagram can be drawn. Correct the air flow rate according to formula (B1) for each measurement time and measurement volume.
p× V× 60 - 0.584 p× V
102.8 X t
Where: 9-
(B1)
Air flow rate, expressed in mL/min, calibrated to 102.8 kPaL] [the sum of normal atmospheric pressure (101.3 kPa) and operating pressure at 23°C (1.47 kPa)];
Volumeter volume, mL;
Time for soap bubbles to pass between two scales of the volumemeter, s; p-
The sum of actual atmospheric pressure and (water column) pressure gauge, expressed in kPa. B3 Capillary Calibration
Connect the capillary between the outlet of the Bentsen flowmeter and point A of the soap bubble meter, and remove the control valve and the tube on the top of the volume meter. Determine the time for the soap bubble to pass through according to B2.2, and calculate the air flow according to B2.3. 269
Additional Notes:
This standard was proposed by the China Light Industry General Association.
GB/T 2679.4—94
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by the Guangdong Paper Research Institute. The main drafters of this standard are Sun Shaofang and Chen Xi. This standard was first issued in August 1981.The 47kPa pressure regulating valve is placed on the shaft and rotated. The vent valve is opened, and the air flow is directed from the flow meter to the soap bubble meter for calibration. Carefully adjust the pipe clamp and the needle valve to make the flow rate of the flow meter constant. Quickly squeeze the rubber ball at the bottom of the volume meter to allow the soap bubble to enter the volume meter. Measure the time for the soap bubble to pass between the two scales of the calibrated volume, expressed in seconds. The range of the selected volume meter should allow the measurement time to exceed 30s. Repeat the measurement of 6 different air flows and record the atmospheric pressure at that time.
GB/T2679.4—94
Figure B1 Soap bubble meter
A-connection point; B—1L glass bottle; C—needle valve; D—volumeter; E—rubber ball Note: The system can produce calibration errors under high air flow pressure drop. In order to eliminate this error, the length and diameter of the pipe must be the same as the test. B2.3 Calculation
Check whether the reading error of the flow meter is within 5%. If not, a correction chart can be drawn. Correct the air flow rate according to formula (B1) from each measurement time and measurement volume.
p× V× 60 - 0. 584 p× V
102. 8 X t
Where: 9-
(B1)
Air flow rate, expressed in mL/min, calibrated to 102.8 kPaL [the sum of normal atmospheric pressure (101.3 kPa) and operating pressure at 23°C (1.47 kPa)];
Volumeter volume, mL;
Time for a soap bubble to pass between two scales of the volumemeter, s; p-
The sum of the actual atmospheric pressure and the (water column) pressure gauge, expressed in kPa. B3 Capillary calibration
Connect a capillary between the outlet of the Bentson flowmeter and point A of the soap bubble meter, removing the control valve and the tube on the top of the volumemeter. Determine the time for soap bubbles to pass through according to B2.2, and calculate the air flow according to B2.3. 269
Additional Notes:
This standard is proposed by China Light Industry General Association.
GB/T 2679.4—94
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by Guangdong Paper Research Institute. The main drafters of this standard are Sun Shaofang and Chen Xi. This standard was first issued in August 1981.The 47kPa pressure regulating valve is placed on the shaft and rotated. The vent valve is opened, and the air flow is directed from the flow meter to the soap bubble meter for calibration. Carefully adjust the pipe clamp and the needle valve to make the flow rate of the flow meter constant. Quickly squeeze the rubber ball at the bottom of the volume meter to allow the soap bubble to enter the volume meter. Measure the time for the soap bubble to pass between the two scales of the calibrated volume, expressed in seconds. The range of the selected volume meter should allow the measurement time to exceed 30s. Repeat the measurement of 6 different air flows and record the atmospheric pressure at that time.
GB/T2679.4—94
Figure B1 Soap bubble meter
A-connection point; B—1L glass bottle; C—needle valve; D—volumeter; E—rubber ball Note: The system can produce calibration errors under high air flow pressure drop. In order to eliminate this error, the length and diameter of the pipe must be the same as the test. B2.3 Calculation
Check whether the reading error of the flow meter is within 5%. If not, a correction chart can be drawn. Correct the air flow rate according to formula (B1) from each measurement time and measurement volume.
p× V× 60 - 0. 584 p× V
102. 8 X t
Where: 9-
(B1)
Air flow rate, expressed in mL/min, calibrated to 102.8 kPaL [the sum of normal atmospheric pressure (101.3 kPa) and operating pressure at 23°C (1.47 kPa)];
Volumeter volume, mL;
Time for a soap bubble to pass between two scales of the volumemeter, s; p-
The sum of the actual atmospheric pressure and the (water column) pressure gauge, expressed in kPa. B3 Capillary calibration
Connect a capillary between the outlet of the Bentson flowmeter and point A of the soap bubble meter, removing the control valve and the tube on the top of the volumemeter. Determine the time for soap bubbles to pass through according to B2.2, and calculate the air flow according to B2.3. 269
Additional Notes:
This standard is proposed by China Light Industry General Association.
GB/T 2679.4—94
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by Guangdong Paper Research Institute. The main drafters of this standard are Sun Shaofang and Chen Xi. This standard was first issued in August 1981.
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