JB/T 7630.1-1998 Ultrafine glass fiber separator for lead-acid batteries
Some standard content:
JB/T 7630.11998
This standard is a revision of JB/T7630-94 "Ultrafine glass fiber separator for lead-acid batteries". In the revision, reference was made to Japan's JIS C2202-1995 "Glass wool for lead-acid batteries", JIS C2313-1990 "Separator for lead-acid batteries" and BCI "RBSM standard test method", but the technical contents are not equivalent. The format and rules of this standard are all based on GB/T1.1-1993 "Guidelines for standardization work" to ensure the uniformity of standard writing and to be suitable for international exchanges.
This standard is the first standard in the series of lead-acid battery separator standards. The original standard quoted other standards that were not detailed in this standard. This standard gives detailed descriptions. In addition, compared with JB/T7630-94, this standard has the following changes: Added preface; Chapters and sections are rearranged according to the changes in content; 1 (modified scope);
-3 (added definition);
-4 (modified classification, naming and marking); -5.2.2 (modified tt||5.3 (modify the tensile strength, resistance, pore size, and porosity of sheet-type separators, the 24h capillary acid absorption height of felt-type separators, and the limit values of iron content);
-6.1 (add sampling);
-6.2 (add sample state adjustment and standard environment); -6.4 (modify the test method for sheet-type separator thickness); -6.5 (modify the sample size for sheet-type separator tensile strength and the calculation formula for the average thickness of ribbed separators); -6.6 (Modify the resistance test steps and the calculation formula of resistance, and add the method of resistance test by resistance method); 6.8 (Modify the porosity test steps, cancel the porosity test with liquid specific gravity balance); 6.9 (Modify the preparation and test steps of the sample for wettability determination); -6.10 (Modify the quantitative test steps and calculation formula); -6.12.4.1 (Modify the test steps of acid immersion weight loss of sheet-type separator); -6.17 (Add the determination of foaming property);
-7.1 (Modify the test points Category);
7.3 (add batching rules and sampling plans);--6.5.1, 6.6.1, 6.7.1, 6.8.1, 6.9.1, 6.10.1, 6.11.1, 6.12.1, 6.17.1 (add determination principle)3-6.3.2, 6.5.5, 6.6.5, 6.7.5, 6.8.5, 6.9.5, 6.10.5, 6.11.4, 6.12.5, 6.17.5 add result determination). From the date of entry into force, this standard will replace JB/T7630--94. This standard is proposed and managed by the National Lead-acid Battery Standardization Technical Committee. This standard was drafted by the Shenyang Battery Research Institute, and Fuzhou Battery General Factory and Hebei Handan Hengyong Protective Clean Products Co., Ltd. participated in the drafting.
The main drafters of this standard are Sun Xueli, Xie Shuang, Sheng Lin, Li Fuzhao and Su Mansheng. This standard was first issued in December 1994 and revised for the first time in 1997. 250
1 Scope
Machinery Industry Standard of the People's Republic of China
Microglass fiber separator for lead acid storage batteries
JB/T 7630. 1-1998
Replaces JB/T7630-—94
This standard specifies the definition, classification, naming and marking, required measurement methods, inspection rules, marking, packaging, transportation and storage of microglass fiber separators for lead acid storage batteries (hereinafter referred to as separators). This standard applies to separators for lead acid batteries. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T 625—1989
GB/T 626-
GB/T 631—1989
GB/T 643--1988
GB/T 661—1992
GB/T 670-1986
GB/T 676--1990
GB/T 693-—-1985
GB/T 1250-1989
GB 1253---1989
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Chemical reagents
Potassium permanganate
Ammonium ferrous sulfate (II) hexahydrate (ammonium ferrous sulfate)Silver nitrate
Acetic acid (glacial acetic acid)
Sodium acetate
Methods of expressing and determining limits
Working reference reagent (volume) Sodium chloride
Working reference reagent (volume) Sodium oxalate
GB 1254--1990
GB/T1293—1989
Chemical reagents 1,10-phenanthroline
Standard environment for conditioning and testing of plastic specimens GB/T 2918--1982
GB/T 6685—1986
Chemical reagents Hydroxylamine chloride (Hydroxylamine hydrochloride) GB/T 8170—1987
Rules for rounding off values
GB/T 14436—1993
3 Industrial product guarantee documents
JB/T2599—1993 Method for compiling lead-acid battery product models 3 Definitions
This standard adopts the following definitions.
3.1 Maximum pore size
The diameter of the largest pore in the separator.
3.2 Porosity
Approved by the Ministry of Machinery Industry on May 28, 1998
Implemented on November 1, 1998
The percentage of the volume of the partition pores to the volume of the entire partition. 3.3 Resistance
The ability of the partition to hinder the electrical migration of ions in sulfuric acid solution, expressed in ohms per square decimeter per partition. 3.4 Wettability
The ability of the partition to be wetted by sulfuric acid solution, expressed in time. 3.5 Quantification
The mass of the partition per unit area and unit thickness. 3.6 Acid immersion weight loss
The change in mass of the partition after being immersed in a sulfuric acid solution of a certain temperature and density for a certain period of time. 3.7 Capillary acid absorption height
The height to which the acid solution climbs freely when the partition absorbs acid. 3.8 Foaming property
The ability of the separator to produce bubbles (foam) on the surface of sulfuric acid solution under constant current charging. 4 Classification, naming and marking of separators
4.1 Classification
Separators are divided into sheet-type separators (including flat plate, ribbed strip, grooved, composite), felt-type separators and bag-type separators according to their types. 4.2 Naming and marking
Separators are named and marked in capital letters of Chinese pinyin, and are composed as follows: (□XX□)
-total thickness of separator, mm
Width of separator, mm
Height of separator, mm||tt ||The first Chinese letter of the Chinese character for partition is G; the first Chinese letter of the Chinese character for glass fiber and the Chinese character for fiber of the partition main body is BX: the first Chinese letter of the Chinese character for partition type is P for sheet type, Z for felt type, and D for bag type;
For lead-acid battery product models, see IB/T2599, such as: the naming and marking of the starting type sheet glass fiber partition with a height of 146mm, a width of 148mm, and a total thickness of 1.5mm is: Q-PBXG (146 mmX148mmX1.5 mm). 5 Requirements
5.1 Appearance
The surface of the partition is flat, the color is uniform, and there are no defects such as cracks, perforations, missing corners, and delamination. 5.2 Specifications and dimensions
5.2.1 The specifications and dimensions shall comply with the product drawing requirements of the manufacturer or the product drawing requirements agreed upon by the user and the manufacturer. 5.2.2 The dimensional deviation shall comply with the provisions of Table 1 when there are no special requirements in the product drawing. 5.3 Physical and chemical properties
Physical and chemical properties are shown in Table 2.
Note: d is the total thickness.
Tensile strength
Basic dimensions
Resistance, 2·dm2
Maximum pore size, μm
Porosity, %
Wettability, s
Quantitative,g/m2·mm
Capillary acid absorption height,
mm/5 min
mm/24h
Reducing potassium permanganate substances, mL/g
Pickling weight loss, %
Iron content, %
Chlorine content %
Water content, %
Foaming property
JB/T 7630.1-1998
Table 1 Dimension deviation
Table 2 Physical and chemical properties
Sheet type, bag type partition, MPa
Ordinary type 1)
≤0.00103)
Diagonal
Limit value
Felt type partition
Total thickness, mm
>0.30~～0.50
>0.50~~0.70
>0. 70~1. 00
>1, 00~1, 50
>1. 50~2. 50
Composite type?
≤0.0015
Total thickness, mm
>1. 00~2. 00
≥140
≥620
Base thickness
+8: 82
Limit value
≤0.00050
≤0.00060
Bubbles (foam) cannot completely cover the surface of sulfuric acid solution1) Ordinary separator refers to the separator without coarse glass fiber attached to the outer layer. 2) Composite separator refers to the separator with coarse glass fiber attached to the outer layer. 3) The total thickness of the separator corresponding to this resistance limit value is not more than 2.0mm. 5.4 Storage period
The storage period of the separator is one year.
6 Determination method
6.1 Sampling
6.1.1 Sampling conditions
JB/T 7630.1—1998
The products must be placed in the production site, use site or warehouse at room temperature. 6.1.2 Sampling method
Sampling shall be carried out by random sampling. Sheet-type and bag-type partitions or felt-type partitions cut into sheets shall be taken from at least three packages; roll partitions shall be cut from each of the three rolls in at least three packages along the length direction. The sample units are shown in Table 5.6.1.3 Sample preservation method
The randomly selected samples must be placed in the standard environment specified in GB/T2918 and covered to prevent dust accumulation, mechanical damage, etc. 6.2 Sample state adjustment and standard environmentwwW.bzxz.Net
The sample must be adjusted in the standard environment for no less than 24 hours. The test environment shall be carried out in accordance with the GB/T2918 regulations unless otherwise specified. 6.3 Appearance inspection
6.3.1 Inspection method
Visually inspect the surface color of the partition in a brightly lit room to check whether there is any missing corner. In a dark room, prepare a light-transmitting box with a 100W incandescent bulb or a 40W fluorescent tube. The light-transmitting side is equipped with a glass plate (100mm away from the light source in the box). Place the partition flat on the glass plate and observe with your eyes whether there are defects such as cracks and perforations on the partition. 6.3.2 Result determination
If the number of samples with the above defects accounts for 0.2% or less of the total number, the item is qualified. If it exceeds 0.2%, the item is unqualified and the batch of products is unqualified.
6.4 Determination of overall dimensions
6.4.1 Determination of height, width and diagonal
Put the sample flat on a horizontal surface and measure the height, width and diagonal of the sample with a universal measuring tool with a graduation value of 0.5mm. 6.4.2 Determination of thickness
6.4.2.1 Instrument
The thickness gauge should meet the following conditions:
Division value of dial indicator 0.01mm
--diameter of measuring head 28mm;
-contact pressure 10 kPa±1kPa.
6.4.2.2 Preparation of test specimens
a) For felt-type partitions and flat-plate partitions, cut five test specimens of about 100mm×100mm. If the sample is smaller than this size but not less than 35mm×35mm, five square test specimens can be cut according to the actual size; b) For other partitions, when measuring the base thickness, cut five test specimens of about 100mm in length and as wide as possible. If the sample size is less than 100mm, the actual length is the length of the test specimen.
When measuring the total thickness, the sample is used as the test specimen. If the sample is a rolled partition, cut five test specimens of about 100mm×100mm. 6.4.2.3 Test steps
Adjust the zero point of the dial indicator of the thickness gauge, lift the measuring head and place the sample on the measuring surface. For felt-type partitions, press the measuring head on the sample at a speed lower than 3mm/s, and for other partitions, press the measuring head on the sample at a speed of about 6mm/s. The sample should not be impacted. Read the indicated value after the dial indicator pointer stabilizes. 6.4.2.4 Calculation of results
Each sample is tested at three points evenly distributed, and the arithmetic mean is taken. Then the arithmetic mean is taken for five samples. For felt-type partition samples smaller than 100mm×100mm, one point is tested for each sample, and the arithmetic mean is taken. Round off to three significant figures. 6.5 Determination of tensile strength
6.5.1 Principle
JB/T 7630. 1--1998
Tensile strength can be obtained by testing the sample at a constant speed on a special testing machine. Sheet-type and bag-type partitions are expressed in terms of the maximum force per unit cross-sectional area of the sample, and felt-type partitions are expressed in terms of the maximum force per unit width of the sample. 6.5.2 Device
Tensile machine.
6.5.3 Preparation of samples
Five samples of sheet and bag type partitions are cut along the partition forming direction. The sample length is 70mm and the width is 10mm. The front ribs of the ribbed partition are in the middle of the sample. The convex and concave grooves of the grooved partition are taken in half. Marks of 30mm clamping distance are made on the sample. Five samples of felt type partitions are cut along the partition forming direction. The sample length is 100mm and the width is 15mm. Marks of 50mm clamping distance are made on the sample.
6.5.4 Test steps
Clamp the sample on the upper and lower clamps of the tensile machine. During the test, the sample should be clamped tightly and cannot slide or damage the sample. The center line of the clamp should be coaxial with the center line of the sample. The sheet type and bag type partition samples are stretched at a speed of 200mm/min±20mm/min, and the felt type partition samples are stretched at a speed of 25mm/min±5mm/min. Record the load when the sample is destroyed. When the forming direction of the specimen cannot be distinguished, five specimens should be taken in the length and width directions respectively, and the group with the higher measured data shall be the specimen breaking load. If the specimen is broken at the clamping position, the test is invalid, and additional specimens shall be added for retesting. 6.5.5 Calculation and determination of results
The tensile strength of sheet and bag-type partition specimens shall be calculated according to formula (1): P
b·d average
Where: 8f
Tensile strength, MPa;
PSpecimen breaking load, N;
b-specimen width, mm;
Average specimen thickness, mm.
The average thickness of the ribbed partition specimen is calculated according to formula (2): ds = dbase+n+)bu(+)dsugar(+)nc-)bm(-)denzyme(II)6
Wherein: daverage specimen thickness, mm;
-sample base thickness, mm;
drib(+) —
sample front rib thickness, mm;
drib() —
sample negative rib thickness, mm; b<+)
brib() —
sample front rib width, mm;
sample negative rib width, mm;
b —sample width, mm;
sample front rib number;
sample negative rib number.
The tensile strength of the felt partition sample is calculated according to formula (3): =
Where:?—tensile strength, kN/m;
P-—destructive load of the sample, N;
b—sample width, mm.
The result is expressed as the arithmetic mean of the measured values of five samples, rounded to three significant figures, (1))
(2)
(3)
The measured value of the sample shall not deviate from the arithmetic mean by more than 15%, otherwise it shall be discarded, but the total number of discarded samples shall not exceed 40%, otherwise additional samples shall be re-measured. If the test results of two or more samples are unqualified, double sampling shall be required for measurement. If the results are still unqualified, the batch of products shall be unqualified.
6.6 Determination of resistance
6.6.1 Principle
In sulfuric acid solution, since the partition hinders the migration of ions, under constant current conditions, the potential and resistance will change before and after the partition is inserted, and the partition resistance can be calculated from this.
6.6.2 Instruments, devices and reagents
Test tank (see Figure 1);
Figure 1 Schematic diagram of test tank
Acid immersion tank: internal dimensions, 100mm×150mm×200mm; positive and negative plates of lead-acid battery for dry-type charged starting; DC current stabilizer: range 0~10A;
DC voltmeter: accuracy level 0.5, range 0~300mV, internal resistance greater than 300Q/V; DC ammeter: accuracy level 0.5, range 0~5A; 256
JB/T7630.1—1998
Cadmium electrode: diameter 8mm~~10mm, length 120mm~150 mm;-Paper cutter;
Sulfuric acid: analytical grade, density 1.280g/cm2±0.005g/cm2 (25℃). 6.6.3 Preparation of samples
Cut the samples into 142mm×146mm samples. If the sample size is less than 142mm×146mm, cut it into at least 125mm×135mm samples. The number of samples in each group shall not be less than that specified in Table 3. Place the cut samples in the acid immersion tank so that the samples are completely immersed in 25℃±2℃ density 1.280g/cm2±0.005g/cm2 sulfuric acid solution. The acid immersion time is 1~～5h, limited to the sample immersion; the separator for starting dry charged battery is soaked for 20min, and the felt separator is not acid-immersed. 6.6.4 Test steps
6.6.4.1 Voltage method
Adjust the temperature of the sulfuric acid solution in the test tank to 25℃±2℃, adjust the density of the sulfuric acid solution to 1.280g/cm2±0.005g/cm2, connect the circuit as shown in Figure 2, and charge at a constant current of 1A~3A until the voltage of the cadmium electrode stabilizes. 3
1--DC current stabilizer; 2--ammeter; 3--voltmeter; 4--cadmium electrode 5--acid-resistant container; 6--plate Figure 2 Resistance test circuit diagram
Adjust the DC current stabilizer knob to adjust the current to 1.0A. After the ammeter stabilizes, record the blank cadmium electrode voltage. Then, according to Table 3, take out the sample from the acid immersion tank and insert it (the felt partition is directly inserted into the test tank. If there is a gap between the samples, a plastic clamp should be used to clamp the sample. After the cadmium electrode voltage stabilizes, record the voltage. 6.6.4.2 Resistance method determination
Adjust the temperature of the sulfuric acid solution in the test tank to 25℃±2℃, and adjust the density of the sulfuric acid solution to 1.280g/cm2±0.005 g/cm2, turn on the circuit to fully charge the plate, and record the resistance after the milliohmmeter stabilizes. Then take out the sample from the acid immersion tank and insert it into the test tank (felt-type partition is directly inserted) according to the provisions of Table 3. If there is a gap between the samples, a plastic clamp should be used to clamp the sample. After the milliohmmeter stabilizes, record the resistance.
6.6.5 Result calculation and judgment
The voltage method is calculated according to formula (4):
Where: R——sample resistance, Q·dm2; V.
-Cadmium electrode voltage before inserting the sample, V;
Vi——Cadmium electrode voltage after inserting the sample, V; S effective test area of the sample, 1dm2;
R= (Vi-Vo).S
-current, A;
number of inserted test pieces.
The resistance method is calculated according to formula (5)
where: R--resistance of the test piece, 2·dm2;
JB/T 7630.1-—1998
RR.
X 10-3
R. —resistance before inserting the test piece, mQ·dm2R,-resistance after inserting the test piece, mQ·dm2;
number of inserted test pieces.
For tests conducted twice or more (including twice), the arithmetic mean of the test results shall be taken and rounded to two significant figures. (5)
For the results of two or more tests, the deviation between each test result and the arithmetic mean shall not exceed 10%. Otherwise, add a sample and recalculate. If one of the test results is unqualified, double sampling is required for testing. If the result is still unqualified, the batch of products is unqualified. Table 3 Resistance test Number of test pieces inserted
Number of test pieces inserted
Number of test pieces
Sheet type, bag type partition
>1.00>1.20>1.30>1.50|>1.80>2.201.20
Felt type partition
>2. 70≤1. 00
1 The results of the voltage method and the resistance method are equally valid. However, if there is a dispute between the two methods, the voltage method shall prevail. 5
2 If the resistance of the separator for starting dry-type charged batteries fails to meet the requirements when soaked for 20 minutes, but meets the requirements after soaking for more than 20 minutes, the separator is suitable for non-dry-type charged batteries.
6.7 Determination of the maximum pore size
6.7.1 Principle
The maximum pore size of the separator is determined by the bubble method. Consider each small hole of the partition as a capillary, moisten the partition with isopropyl alcohol and apply hydraulic pressure to the partition. When the external air pressure in the opposite direction reaches a certain value, bubbles will first emerge from the largest hole of the partition. The relationship between the diameter of this hole and the pressure difference at this time is:
Wherein: Φ
maximum hole diameter of the partition, um;
gravitational acceleration of the test ground, cm/s2;
4α.coso.
pr hi pz hz
surface tension of isopropyl alcohol at test temperature t, dyn/cm; density of water or mercury in the U-type pressure gauge, g/cm; -height difference of water or mercury column in the U-type pressure gauge, cm; density of isopropyl alcohol at test temperature t, g/cm; height of isopropyl alcohol injected, usually 2 cm. Instruments, devices and reagents
U-type pressure gauge: graduation value 1mm;
-sample cutter;
air compressor or air source;
isopropanol: analytical grade.
The device is shown in Figure 3
6.7.3 Preparation of samples
JB/T7630.1—1998
1—isopropanol; 2—cover cap; 3 sample; 4—pore gauge; 5—switch; 6—pressure reducing valve; 7—adjusting switch; 8—U-type pressure gaugeFigure 3 Schematic diagram of the maximum aperture test device
Cut five samples with a diameter of 50mm to 65mm on the sample cutter, number them and immerse them in isopropanol for 10 minutes. For samples with thicker ribs, the ribs around the sample can be cut off. 6.7.4 Test steps
Adjust the air source switch to control the compressed air pressure at 0.10MPa±0.01MPa; adjust the regulating switch so that the water column rising speed of the U-type pressure gauge is 5mm/s±1mm/s; place the sample on the hole meter, pad it with a rubber pad, tighten the cover cap, and fill it with isopropyl alcohol; close the switch at the bottom of the hole meter and pass compressed air. When the first bubble appears on the liquid surface, record the height difference of the water column in the U-type pressure gauge and the room temperature. 6.7.5 Result calculation and judgment
The maximum pore size of the sample is calculated according to formula (6).
The result is expressed as the arithmetic mean of the measured values of the five samples, rounded to two significant figures. The deviation between the measured result and the arithmetic mean value of each measurement shall not exceed 15%, otherwise it shall be discarded, but the total number of discarded values shall not exceed 40%, otherwise additional samples shall be re-measured. If the measurement results of two or more samples are unqualified, double sampling shall be required for measurement. If the results are still unqualified, the batch of products shall be unqualified.
Contact angle of isopropanol 9, a 0°.
2Surface tension (α) and density (p2) of isopropanol at different temperatures are shown in Table 4. 259
6.8 Determination of porosity
6.8.1 Principle
JB/T 7630.1—1998
Table 4 Relationship between surface tension (α.) and density (o2) of isopropanol at test temperature (t)αt
dyn/cm
The porosity of the partition is determined by the buoyancy method.
Porosity of partition-
dyn/cm
The mass of the sample after being circulated in the liquid-The mass of the sample after being saturated with liquid × 100%The mass of the sample The porosity of the partition is calculated by testing the mass of the sample in different states. 6.8.2 Instruments and devices
Analytical balance: sensitivity 0.001g or above;
Sample cutter;
Dryer;
Constant temperature drying oven;
Petri dish;
Beaker.
6.8.3 Preparation of samples
JB/T 7630. 1—-1998
Cut five samples with a diameter of 50mm to 60mm on the sample cutter, dry them at 70℃±2℃ for 2h, and then cool the samples in a dryer to room temperature.
6.8.4 Test steps
Accurately weigh the sample, then place it in a petri dish or beaker, add 70℃±2℃ distilled water, soak for more than 3h (felt-type partitions are soaked in 25℃±2℃ distilled water for 20min~30min), until the sample is completely saturated, push a piece of highly hygroscopic cotton cloth to absorb enough distilled water (limited to no dripping when lifted), take out the sample from the distilled water cooled to room temperature, gently wipe it on the cotton cloth so that there are no water drops on the surface of the sample, immediately weigh the sample, and read the value within 5s; then weigh the mass of the sample in the distilled water (the sample cannot be close to the wall of the cup). 6.8.5 Calculation and judgment of results
The porosity of the sample is calculated according to formula (7):
A = m=m ×100%..
Where: A——porosity of the sample, %;
m—mass of the sample, g;
m1—mass of the sample after saturation, g;
m2—mass of the sample in distilled water, g. The result is expressed as the arithmetic mean of the values of the five samples, rounded to two significant figures. (7)
The deviation of each measurement result from the arithmetic mean shall not exceed 10%, otherwise it shall be discarded, but the total number of discarded values shall not exceed 40%, otherwise additional samples shall be re-measured. If two or more test results are unqualified, double sampling shall be required for measurement. If the results are still unqualified, the batch of products shall be unqualified.
6.9 Determination of wettability
6.9.1 Principle
The partition is placed on the surface of sulfuric acid solution. The sulfuric acid solution is distributed and wetted under the action of intermolecular force on the surface of the partition material. The time required for the sulfuric acid solution to completely wet a certain area of the partition is expressed. 6.9.2 Apparatus and reagents
—Stopwatch: graduation value 0.1s;
—Acid-resistant container: specification 160mmX160mmX50mm; sulfuric acid: analytical grade, density 1.280g/cm2±0.005g/cm2 (25℃). 6.9.3 Preparation of samples
Cut five samples of 140mm×142mm. If the sample size is smaller than the standard sample, the actual size shall prevail. If the sample is cut from the raw material before cutting, its size cannot be less than 100mm×100mm. 6.9.4 Test steps
Add sulfuric acid solution to an acid-resistant container, add sulfuric acid solution about two-thirds of the container volume, keep the acid temperature at 23℃~25℃, place the sample face up on the sulfuric acid liquid surface, no enclosed gas is allowed between the sample and the liquid surface, and immediately record the time when the sample is completely wetted, accurate to 0.1s.
6.9.5 Result determination
Expressed as the arithmetic mean of the measured values of the five samples, rounded to two significant figures. The deviation of each measurement result from the arithmetic mean value shall not exceed 15%, otherwise it shall be discarded, but the total number discarded shall not exceed 40%, otherwise additional samples shall be re-measured. If the measurement results of two or more samples are unqualified, double sampling shall be required for measurement. If the results are still unqualified, the batch of products is unqualified.
6.10 Quantitative determination
6.10.1 Principle
Weigh the mass of the felt-type partition per unit volume and express it in grams per square meter and per millimeter thickness of the felt-type partition.
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