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GB/T 12385-2008 English PDF (GBT12385-2008)

GB/T 12385-2008 English PDF (GBT12385-2008)

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GB/T 12385-2008: Standard test method for sealability of gaskets for pipe flanges

This Standard specifies 2 test methods, Method A and Method B, for the sealability of gaskets for pipe flanges. The 2 test methods of this Standard are applicable to asbestos rubber gaskets, non-asbestos rubber gaskets, rubber gaskets, Teflon gaskets, expanded or modified Teflon gasket, flexible graphite composite gaskets, spiral wound gaskets, metallic clad gaskets, Teflon clad gaskets and gaskets of serrated metal, corrugated metal and waveform serrated metal with non-metallic coating. They are also applicable to metallic flat gaskets.
GB/T ??12385?€?2008
GB
ICS 23.040.60
J 15
National Standard
of the People's Republic of China
Replacing GB/T 12385-1990
Standard test method for sealability of
gaskets for pipe flanges
ISSUED ON. MAY 7, 2008
IMPLEMENTED ON. NOVEMBER 1, 2008
Issued by. State Administration for Quality Supervision, Inspection and Quarantine of the People's Republic of China;
Standardization Administration of China.
Table of Contents
Foreword??...??3
1 Scope??...??4
2 Test??Method??A??...??4
3 Test??method??B...??8
4 Test??report??...??11
Foreword
This Standard is revision to GB/T 12385-1990 Standard Test Method for Sealability of Gaskets for Pipe Flanges. Compared with GB/T 12385-1990, the main changes are as follows.
?€? The applicable scope of the Standard is modified. Add the non-asbestos rubber gaskets, rubber gaskets, Teflon gaskets. Expand or modify Teflon gaskets, flexible graphite composite gaskets, and gaskets of serrated metal, corrugated metal and waveform serrated metal with non-metallic coating;
?€? Rules and regulations are supplemented for the added gasket types, including sample pretreatment method, gasket preload stress, test temperature, test medium pressure and so forth;
?€? Referring to ASTM F112 and F37, pressure drop method is adopted for the measurement of leakage rate in test method B. And test apparatus, test procedures and the calculation of leakage rate are changed accordingly;
?€? General provisions for the key measuring instruments are added;
?€? Provisions for the number of tests and the test report content are added. This standard replaces GB/T 12385-1990, from the date of implementation. This Standard was proposed by China Machinery Industry Federation (CMIF). This standard shall be centralized by National Pipe Accessories Standardization Technical Committee.
Drafting organizations of this Standard. Nanjing Tech University, China Productivity Center for Machinery (CPCFM), Zhejiang Cathay Packing and Sealing Co., Ltd., Ningbo Tiansheng Sealing Packing Co., Ltd., Ningbo IDT Sinyuan Sealing Technology Co., Ltd., National Non-metallic Mineral Products Quality Supervision and Inspection Center, and East China University of Science and Technology.
The main drafters of this Standard. Gu Boqin, Li Junying, Wu Yimin, Cai Renliang, Chen Ye, Li Xinggen, Yuan Yilin, Lei Jianbin, and Feng Mei.
Previous version of the standard replaced by this Standard are as follows. ?€? GB/T 12385-1990.
Standard test method for sealability of gaskets for pipe flanges
1 Scope
This Standard specifies 2 test methods, Method A and Method B, for the sealability of gaskets for pipe flanges.
The 2 test methods of this Standard are applicable to asbestos rubber gaskets, non-asbestos rubber gaskets, rubber gaskets, Teflon gaskets, expanded or modified Teflon gasket, flexible graphite composite gaskets, spiral wound gaskets, metallic clad gaskets, Teflon clad gaskets and gaskets of serrated metal, corrugated metal and waveform serrated metal with non-metallic coating. They are also applicable to metallic flat gaskets.
2 Test??Method??A
2.1 Test apparatus
2.1.1 The test shall be carried out on dedicated test apparatus for the comprehensive performance of gasket. The test apparatus consists of gasket loading system, medium supply system, leak detection system and test flanges, etc., as shown in Figure 1. 1 Standard vessel;
2 leak detection chamber;
3 Simulation flange;
8 calibration gas source;
9 Displacement sensor;
10 Load Sensor;
4 Gasket;
5 Cylinder;
6 Pressure source;
7 Test medium;
11 Pressure sensor;
12 Temperature sensor;
13 Micro-pressure sensor;
14 Data collection system.
Figure 1 Test apparatus of gasket sealability - Test method A
2.1.2 Gasket loading system shall be able to provide the required gasket preload stress. And it can control the constant loading and unloading speed. Fluctuations of the gasket preload stress during the test shall be within ?? 2% of the specified value. When the gasket preload stress is not greater than 35 MPa, the speed of loading and unloading is 0.2 MPa/s. When the gasket preload stress is greater than 35 MPa, the speed of loading and unloading is 0.5 MPa/s.
2.1.3 Test medium supply system shall be able to provide the required test medium pressure. Fluctuations of the medium pressure during the test shall be within ?? 2% of the specified value range.
2.1.4 Pressurization method of leak detection chamber shall be adopted for the measuring of the leakage rate. It is calculated based on the ideal gas law. A sealed circular leak detection chamber shall be set BETWEEN the external gasket AND in-between the upper and lower flanges. The capacity Vc of the leak detection chamber shall be strictly calibrated. The resolution ratio of the leak detection system shall not be lower than 10-5 cm 3/s.
2.1.5 The test flange uses simulation flange, and the sealing surface is a plane. The ratio of flange thickness to diameter shall not be less than 1/3, the elasticity modulus of the flange material shall be 195 GPa-210 GPa, the rigidity of the sealing surface shall be 40HRC- 50HRC, and the surface roughness Ra shall be within the range of 3.2 ??m to 6.3 ??m.
2.1.6 The measuring range of the pressure sensor for measuring test medium pressure shall not be greater than 10 MPa, the error shall not be greater than 0.5% of the full range, and the resolution shall not be less than 1 kPa.
2.1.7 The measuring range of the temperature sensor for the leak detection chamber shall not exceed 32??C, the error shall not be greater than 0.5% of the full range, and the resolution shall not be less than 0.01??C.
2.1.8 The measuring range of the pressure sensor for measuring the micro-pressure of the leak detection chamber shall not be greater than 5 MPa, the error shall not be greater than 0.5% of the full range, and the resolution shall not be less than 0.5 kPa. 2.2 Sample
2.2.1 The sample selected shall be placed at an environment with a temperature between 21??C and 30??C, and a relative humidity of (50??6) % for at least 48h. 2.2.2 Unless otherwise specified, nominal diameter of the sample is DN80 and nominal pressure is not greater than PN50.
2.3 Test conditions
Unless otherwise specified, the test conditions shall be according to the provisions in Table 1.
Table 1 Test conditions
Test sample name
Gasket
preload
stress MPa
Test
temperature ??C Test medium
Test medium
pressure MPa
Asbestos rubber gasket 40
23??5
99.9% of
industrial
nitrogen
4.0
Non-asbestos rubber gasket,
Teflon gasket and modified Teflon
gasket
35 4.0
Expanded Teflon gasket 25 4.0
Rubber gaskets 7 1.0
Flexible graphite composite
gasket 35
1.1 times of
nominal
pressure
Serrated metal, corrugated metal
and waveform serrated metal
gaskets with non-metallic coating
1.1 times of
nominal
pressure
Metal coated pads 60
1.1 times of
nominal
pressure
Teflon coated pads 35
1.1 times of
nominal
pressure
spiral wound gasket 70
1.1 times of
nominal
pressure
2.4 Test procedures
2.4.1 Clean flange sealing surface with solvent (such as acetone) carefully and install the gasket in the center.
2.4.2 According to the regulations of Table 1, apply preload stress to the gasket to reach the specified value and then maintain for 15 minutes.
2.4.3 Calibrate the volume of the leak detection chamber.
2.4.3.1 Calibrate the volume of the leak detection chamber according to Formula (1). Where.
Vc ?€? The volume of the leak detection chamber, the unit is in cm3;
VB ?€? The volume of the standard vessel, the unit is in cm3;
PB ?€? The initial absolute pressure of the standard container, the unit is in Pa; Pc ?€? The absolute pressure of the test medium into the leak detection chamber, the unit is in Pa;
P2v ?€? The absolute pressure after the connection of the standard vessel and the leak detection chamber, the unit is in Pa.
2.4.3.2 The above calibration shall be repeated for 3 times, and the arithmetic average of the 3 measured value Vc shall be regarded as the volume of the leak detection chamber. The deviation of the measured value Vc of each time shall not be greater than 3% to the average value.
2.4.4 According to the provisions of Table 1, the test medium is accessed into it. Maintain for 10 minutes after the medium pressure reaches the specified value. 2.4.5 Start to test the leakage. At the beginning, record the initial pressure P1 and temperature T1 of the leak detection chamber. And start the timing. At the end of test, record the pressure P2 and temperature T2. The measuring time is determined upon the leakage rate. It is usually 2 minutes - 10 minutes.
2.5 Number of tests
Select several samples from the same sample, and randomly select at least 3 samples for testing.
2.6 Leakage rate calculation and test results
2.6.1 The leakage rate shall be calculated according to formula (2).
Where.
Lv ?€? Volumetric leakage rate, Ncm3/s;
Pst ?€? Atmospheric pressure under standard condition, 101 325 Pa;
Tst ?€? Absolute atmospheric temperature under standard condition, 273.16 K; P1 ?€? The absolute pressure of the leak detection chamber when leak detection starts, the unit is in Pa;
P2 ?€? The absolute pressu...

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