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GB/T 20671.3-2020 English PDF (GBT20671.3-2020)

GB/T 20671.3-2020 English PDF (GBT20671.3-2020)

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GB/T 20671.3-2020: Classification system and test methods for nonmetallic gasket materials -- Part 3: Standard test method for fluid resistance of gasket materials
This Part of GB/T 20671 specifies the classification method, code definition, thickness requirements and measurement methods, sampling and sample adjustment of nonmetallic gasket materials. This Part applies to materials which are made of asbestos, cork, cellulose and other inorganic or organic materials combined with various adhesives or impregnant. It does not apply to rubber product materials, gasket coating materials or multilayer composite gasket materials; but the surface layer single layer material of the multilayer composite gasket material is also suitable for this classification system.
GB/T 20671.3-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.100.60
Q 69
Replacing GB/T 20671.3-2006
Classification system and test methods for
nonmetallic gasket materials - Part 3: Standard test
method for fluid resistance of gasket materials
ISSUED ON: JUNE 02, 2020
IMPLEMENTED ON: APRIL 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative references ... 6
3 Principle ... 7
4 Instruments and apparatuses ... 7
5 Test sample ... 8
6 Test procedure ... 9
7 Test report ... 13
8 Precision ... 13
Appendix A (Informative) Test liquid ... 15
Appendix B (Informative) Procedure for determining the volume change rate after immersion ... 16
Classification system and test methods for
nonmetallic gasket materials - Part 3: Standard test
method for fluid resistance of gasket materials
Caution -- The personnel who uses this Standard shall have hands-on
experience in formal laboratory work. This Standard does not address all possible security issues. It is the responsibility of the user to take
appropriate safety and health measures and to ensure compliance with
the conditions which are set by the relevant national regulations.
1 Scope
This Part of GB/T 20671 specifies the principle, instruments and apparatuses, test samples, test procedures, test reports and precision of the method for determining the degree of influence on the physical properties of nonmetallic gasket materials after immersion in the test liquid.
This Part applies to the determination of the liquid resistance of Type 1, Type 2, Type 3 and Type 7 materials which are described in GB/T 20671.1-2020.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 20671.1-2020, Classification system and test methods for nonmetallic gasket materials - Part 1: Standard classification system for nonmetallic gasket materials
GB/T 20671.2, Classification system and test methods for nonmetallic gasket materials - Part 2: Standard test method for compressibility and recovery of gasket materials
GB/T 20671.7-2006, Classification system and test methods for nonmetallic gasket materials - Part 7: Standard test methods for tension testing of nonmetallic gasket materials
GB/T 20671.8, Classification system and test methods for nonmetallic gasket materials - Part 8: Standard test method for flexibility of non-metallic gasket materials
4.6 Conditioning box or conditioning room: maintain the temperature at 21 °C ~ 30 °C and the relative humidity at 50% ~ 55%.
4.7 Test tube: the outer diameter is 38 mm; the total length is 305 mm; it is equipped with a compressible plug that is wrapped in aluminum film.
4.8 Immersion container: it is equipped according to the sample size
requirements.
4.9 Flask with condensing reflux device: it is equipped according to the sample size requirements.
4.10 Light metal wire mesh: its size can be put into the immersion container. 4.11 Watch glass or weighing bottle.
4.12 ASTM No. 1 oil (IRM 901), IRM 903 oil, ASTM fuel oil B, distilled water, ethylene glycol, propylene glycol and other required test liquids (see Appendix A).
4.13 Absorbent material: fast filter paper of oil absorption characteristics or similar absorbent material.
5 Test sample
5.1 The test sample shall be die-cut to keep the sample flat, clean and free of protruding fibers, fillers and particles.
5.2 The sample size shall meet the following requirements:
-- The sample that is used to test the thickness, mass and volume change rate after immersion is a single layer; its size shall be a rectangle whose diameter is 25.4 mm × 50.8 mm or a circle whose diameter is 28.6 mm;
-- The sample that is used to test the reduction rate of tensile strength after immersion shall meet the requirements of GB/T 20671.7-2006;
-- The sample that is used to test the compression ratio after immersion shall be a circle whose diameter is 28.6 mm; the number of layers shall meet
the requirements of GB/T 20671.2;
-- The sample that is used to test the flexibility after immersion shall be a single-layer rectangle of 12.7 mm × 152.4 mm.
5.3 The test sample shall be adjusted according to GB/T 20671.1-2020 before the test.
6.2.1 Put the to-be-tested sample into a test tube or flask; each test tube is filled with only one material. Pour a sufficient amount of fresh liquid into the test tube to completely immerse the sample. Plug the stopper that is wrapped in
aluminum film; place it on the bracket of an oven at the temperature that is specified in Table 2.
6.2.2 After reaching the specified test time, take out the sample and
immediately immerse it in a cool (21 °C ~ 30 °C) and unused test liquid of the same kind; place it for 30 min ~ 60 min. Then, remove the sample from the cooled test liquid; immediately use the absorbent material to absorb the excess liquid on the surface of the sample. Be careful when absorbing excess liquid; do not squeeze the sample. When the thickness of the sample exceeds 0.79 mm, the excess liquid on the edge shall also be absorbed.
6.2.3 Perform the compressibility test according to GB/T 20671.2.
6.2.4 Take the arithmetic average of five parallel test results as the report value; round to two decimal places according to GB/T 8170.
6.3 Determination of tensile strength after immersion
6.3.1 Perform according to 6.2.1.
6.3.2 Perform according to 6.2.2.
6.3.3 Perform the tensile strength test according to GB/T 20671.7-2006. 6.3.4 Take the arithmetic average of three parallel test results as the report value; round to two decimal places according to GB/T 8170.
6.4 Determination of thickening rate after immersion
6.4.1 Slowly lower the pressure head of the thickness gauge to contact the sample; measure five readings; take the average value d1.
6.4.2 Put the test sample in the immersion container; use a light metal mesh to separate the sample of one material from the sample of another material and the bottom of the container; ensure that the sample is still immersed in the test liquid. Pour enough fresh test liquid into the immersion container to ensure that the sample is soaked and covered by the liquid.
6.4.3 After reaching the specified test time, take out the sample and
immediately use the absorbent material to absorb the excess liquid on the surface of the sample. Be careful when absorbing excess liquid; do not squeeze the sample.
Take the arithmetic average of three parallel test results as the report value; round to two decimal places according to GB/T 8170.
6.6 Determination of flexibility after immersion
6.6.1 Perform according to 6.2.1.
6.6.2 Perform according to 6.2.2.
6.6.3 After the sample is immersed in the test liquid, test the flexibility of the sample after immersion in accordance with GB/T 20671.8.
6.7 Determination of volume change rate after immersion
6.7.1 Perform the normal temperature immersion in accordance with 6.4.2 and 6.4.3.
6.7.2 Perform the high temperature immersion in accordance with 6.2.1 and 6.2.2.
6.7.3 Perform the operation according to the procedure for determining the volume change rate after immersion (see Appendix B). For materials whose relative density is less than 1.00, a density balance should be used; proceed according to the following procedures:
a) Zero the density balance; ensure that it is not affected by airflow. b) Hang a small metal block (about 5 g) on the scale hook, so that the sample is completely immersed in water.
c) Weigh the mass of the sample in the air.
d) Then, weigh the mass of the sample in distilled water.
e) The original volume V1 value is the mass value of the sample in air minus the mass value of the sample in distilled water.
f) After removing the sample from the test medium, repeat the operations of c), d) and e) to obtain the sample volume V2 after immersion.
Note: Frequently replace distilled water during the test; use the same metal block.
6.7.4 Calculate the volume change rate ΔV according to Formula (3):
Where:
m3 -- the mass of the sample in the air after immersion, in grams (g);
m4 -- the mass of the sample in distilled water after immersion, in grams (g). B.1.9 If the test liquid evaporates at room temperature, the time from the sample is removed from the test liquid to the stopper of the weighing bottle is put on shall not exceed 30 s; the time from the sample is taken out of the weighing bottle to it is immersed in distilled water again shall not exceed 30 s. B.1.10 If the test liquid is a viscous oil, after the sample is taken out from the test liquid at the specified test temperature, do not put it in the cold test liquid again. It shall be directly suspended in a normal temperature test room with no flowing airflow and kept for about 30 minutes, to let most of the oil on the surface of the sample flow away by itself; then, continue the acetone immersion and subsequent operations.
B.1.11 When weighing in distilled water, all bubbles that adhere to the sample shall be removed. If in the process of weighing in distilled water, bubbles appear on the surface of the sample or the calculated volume changes by 0.5% in 5 minutes, the sample is too loose and the volume change rate cannot be
measured by the water drainage method. Use the following method instead: a) If the sample is a simple geometry, directly measure its volume before and after immersion in the test liquid; calculate its volume change rate.
b) If the volume increase after the sample is immersed in the test liquid mainly occurs in the thickness, the change rate of the thickness can be used instead of the volume change rate.
B.1.12 If the sample floats on the liquid, a piece of stainless steel can be used as a ballast, to immerse the sample in the liquid. The following procedures can be used:
a) Weigh the mass of the sample together with the ballast in the water; b) Weigh the mass of the ballast alone in the water;
c) The mass of the sample and the ballast in the water minus the mass of the ballast alone in the water is the mass of the sample in the water. Then, calculate according to Formula (B.1).
B.1.13 When distilled water is used as the test liquid, it is not necessary to immerse the sample in alcohol and acetone before and after immersion.
B.2 Fluid drainage method -- applicable to water-soluble test liquids
(except water)
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