GB/T 12385-2025 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 12385-2025 | English | 275 |
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Standard test methods for sealability of gaskets for pipe flanges
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| GB/T 12385-2008 | English | 90 |
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Standard test method for sealability of gaskets for pipe flanges
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| GB/T 12385-1990 | English | 359 |
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Test method for sealing characteristics of gaskets for pipe flanges
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GB/T 12385-2025: Standard test methods for sealability of gaskets for pipe flanges---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT12385-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.040.60
CCS J 15
Replacing GB/T 12385-2008
Standard Test Methods for Sealability of Gaskets for Pipe
Flanges
Issued on: MARCH 28, 2025
Implemented on: OCTOBER 1, 2025
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative References... 5
3 Terms and Definitions... 5
4 Leak Detection Cavity Pressurization Method (Method A)... 5
5 Pressure Drop Method (Method B)... 10
6 Helium Mass Spectrometry Vacuum Leak Detection Method (Method C)... 13
7 Selection of Test Methods and Precautions... 15
8 Test Report... 16
Foreword
This document was drafted in accordance with the rules provided in GB/T 1.1-2020 Directives
for Standardization - Part 1.Rules for the Structure and Drafting of Standardizing Documents.
This document serves as a replacement for GB/T 12385-2008 Standard Test Method for
Sealability of Gaskets for Pipe Flanges. In comparison with GB/T 12385-2008, apart from
structural adjustments and editorial modifications, the main technical changes are as follows.
a) The Scope is modified (see Chapter 1; Chapter 1 of Version 2008);
b) The asbestos rubber sheet is deleted (see Table 1 of Version 2008);
c) The provisions for specimens, dimensions and dimensional measurements are added
(see 4.3.2, 4.3.3 and 5.3);
d) The helium mass spectrometry vacuum leak detection method (Method C) is added
(see Chapter 6).
Please be noted that certain content of this document may involve patents. The institution
issuing this document does not undertake the responsibility of identifying these patents.
This document was proposed by China Machinery Industry Federation.
This document shall be under the jurisdiction of National Technical Committee 237 on Piping
Fittings of Standardization Administration of China (SAC/TC 237).
The drafting organizations of this document. East China University of Science and Technology;
Zhejiang CPS Cathay Packing & Sealing Co., Ltd.; Ningbo Tiansheng Sealing Parts Co., Ltd.;
China Productivity Center for Machinery Co., Ltd.; Ningbo Yitiandi Xinyuan Sealing
Technology Co., Ltd.; Cixi Hengli Sealing Materials Co., Ltd.; Special Equipment Safety
Supervision Inspection Institute of Jiangsu Province; Guangzhou Dongshan South Seals Co.,
Ltd.; Wuxi Xixi Chemical Machinery Parts Co., Ltd.; Wenzhou Huahai Sealing Co., Ltd.;
Taizhou Longjiang Chemical Machinery Technology Co., Ltd.; SINOPEC Engineering
Incorporation; China Tianchen Engineering Corporation Ltd.; CNPC EastChina Design
Institute Co., Ltd.; Beijing Branch of China Huanqiu Contracting & Engineering Co., Ltd.;
Suzhou Nuclear Power Research Institute; Ningbo Auto Sealing Technology Co., Ltd.; Cixi
AIFLON Sealing Parts Co., Ltd.; Zhejiang Zhengtong Pipes Co., Ltd.; Shenzhen Minle Pipe
Industry Co., Ltd.; Zhejiang Bomeite Energy Equipment Co., Ltd.; Yanqi Lake Institute of
Basic Manufacturing Technology Research Co., Ltd.; Nuclear Industry Research and
Engineering Co., Ltd.
The main drafters of this document. Zhang Lanzhu, Wu Yimin, Li Xinggen, Feng Feng, Lin
Jianhong, Xu Shaohuan, Li Ke, Wu Kaijun, Hui Fuming, Zhang Yong, Xiong Conggui, Zhao
Yong, Liu Hongfu, Liu Jianxin, Pang Dong, Han Chuanwei, Ye Xin, Ye Qiwei, Yang Xin, Xu
Zhihua, Zhang Kemei, Wang Xiaojuan, Chang Haijun.
Standard Test Methods for Sealability of Gaskets for Pipe
Flanges
1 Scope
This document describes three methods for determining the sealability of gaskets used for pipe
flanges. the leak detection cavity pressurization method (Method A), the pressure drop method
(Method B) and the helium mass spectrometry vacuum leak detection method (Method C).
This document is applicable to the determination of the sealability of non-metallic flat gaskets,
spiral wound gaskets, polytetrafluoroethylene coated gaskets, metal coated gaskets, flexible
graphite composite reinforced gaskets, metal toothed combination gaskets and metal corrugated
composite gaskets. Other types of gaskets may take this as a reference.
2 Normative References
This document does not have normative references.
3 Terms and Definitions
This document does not have terms or definitions that need to be defined.
4 Leak Detection Cavity Pressurization Method (Method A)
4.1 Overview
It is applicable to the sealability test of gaskets for pipe flanges with the medium being nitrogen
or helium, and the leakage rate ranging from 105 cm3/s (standard state) to 101 cm3/s (standard
state) (hereinafter referred to as “the gaskets”).
4.2 Test Device
4.2.1 The test device consists of a gasket loading system, a test medium supply system, a leak
detection system and a test flange, as shown in Figure 1.
4.2.2 The gasket loading system shall be able to provide the specified gasket pre-tightening
specific pressure and be able to control constant loading and unloading speeds. During the test,
the fluctuation of the gasket pre-tightening specific pressure shall be 2% of the specified value.
When the gasket pre-tightening specific pressure is less than or equal to 35 MPa, the loading
speed and unloading speeds shall be 0.2 MPa/s; when the gasket pre-tightening specific
pressure is greater than 35 MPa, the loading and unloading speeds shall be 0.5 MPa/s.
PC---the absolute pressure of the test medium introduced into the leak detection cavity,
expressed in (MPa).
4.5.4 In accordance with the provisions of 4.2.3 and Table 1, introduce the test medium, and
after the medium pressure reaches the specified value, maintain it for 10 minutes.
4.5.5 Start leak detection and record the pressure and temperature in the leak detection cavity
at the beginning of the leak detection. Start timing and record the pressure and temperature in
the leak detection cavity at the end of the measurement. The measurement time depends on the
leakage rate and is usually 2 minutes ~ 10 minutes.
4.6 Number of Tests
Select several specimens from the same sample and randomly select no less than 3 specimens
for testing.
4.7 Leakage Rate Calculation and Test Result
4.7.1 The leakage rate calculation is based on the ideal gas law and is calculated in accordance
with Formula (2).
Where,
LNV---when nitrogen is the medium, the volume leakage rate under the standard state, expressed
in (cm3/s) (the standard state);
LHV---when helium is the medium, the volume leakage rate under the standard state, expressed
in (cm3/s) (the standard state);
Tst---the absolute temperature of the atmosphere under the standard state, expressed in (K) (Tst
= 273.16);
Pst---the atmospheric pressure under the standard state, expressed in (MPa) (Pst = 0.101325);
VC---the volume of the leak detection cavity, expressed in (cm3);
t---the leakage detection time, expressed in (s);
P1---the absolute pressure in the leak detection cavity at the beginning of leak detection,
expressed in (MPa);
T1---the absolute temperature of the leak detection cavity at the beginning of leak detection,
4---simulated flange (upper); 13---buffer tank;
5---gasket; 14---pressure source;
6---simulated flange (lower); 15---sealed cavity;
7---oil cylinder; 16---data acquisition system;
8---valve; 17---vent pipeline and valve.
9---standard container;
Figure 2 -- Schematic Diagram of the Test Device for the Pressure Drop Method
5.2.2 The application of the gasket pre-tightening specific pressure shall comply with the
provisions of 4.2.2.
5.2.3 The test medium introduced shall comply with the provisions of 4.2.3.
5.2.4 The leak detection shall adopt the sealed cavity pressure drop method, and the volume VS
of the sealed cavity shall be calibrated.
5.2.5 The measuring range of the pressure sensor shall not be greater than 10 MPa, the error
shall not be greater than 0.5% of the full measuring range, the accuracy class shall not be lower
than Class 0.5, and the resolution shall not be lower than 10 kPa.
5.2.6 The measuring range of the differential pressure sensor shall not be greater than 100 kPa,
the error shall not be greater than 0.5% of the full measuring range, the accuracy class shall not
be lower than Class 0.5, and the resolution shall not be lower than 0.1 kPa.
5.2.7 The test flange shall comply with the provisions of 4.2.5.
5.2.8 The temperature sensor for measuring the temperature of the sealed cavity shall comply
with the provisions of 4.2.7.
5.3 Specimens
The specimen preparation, specimen size and specimen size measurement shall be carried out
in accordance with 4.3.
5.4 Test Conditions
The test conditions are in accordance with 4.4.
5.5 Test Procedures
5.5.1 Use solvent (for example, acetone) to clean the flange sealing surface and install the gasket
in the center.
5.7.1 The leakage rate calculation is based on the ideal gas law and is calculated in accordance
with Formula (4).
Where,
LNV---when nitrogen is the medium, the volume leakage rate under the standard state, expressed
in (cm3/s) (the standard state);
LHV---when helium is the medium, the volume leakage rate under the standard state, expressed
in (cm3/s) (the standard state);
Tst---the absolute temperature of the atmosphere under the standard state, expressed in (K) (Tst
= 273.16);
Pst---the atmospheric pressure under the standard state, expressed in (MPa) (Pst = 0.101325);
VS---the volume of the sealed cavity, expressed in (cm3);
t---the leakage detection time, expressed in (s);
P3---the absolute pressure in the sealed cavity at the beginning of leak detection, expressed in
(MPa);
T3---the absolute temperature of the sealed cavity at the beginning of leak detection, expressed
in (K);
P4---the absolute pressure in the sealed cavity at the end of leak detection, expressed in (MPa);
T4---the absolute temperature of the sealed cavity at the end of leak detection, expressed in (K).
5.7.2 The final test result shall be the arithmetic mean of all calculated values and rounded to
two significant figures.
6 Helium Mass Spectrometry Vacuum Leak Detection
Method (Method C)
6.1 Overview
It is applicable to the sealability test of gaskets with the medium being helium with purity not
lower than 99.9%, and the leakage rate LV ranging from 108 cm3/s (standard state) to 103 cm3/s
(standard state).
The specimen preparation, specimen size and specimen size measurement shall be carried out
in accordance with 4.3.
6.4 Test Conditions
The test conditions are in accordance with 4.4.
6.5 Test Procedures
6.5.1 Use a soft cotton cloth dipped in solvent (for example, acetone) to clean the surfaces of
the upper and lower simulated flanges, and place the gasket between the simulated flanges in
the center.
6.5.2 In accordance with the provisions of 6.2.2 and Table 1, apply the pre-tightening specific
pressure to the gasket, and after reaching the specified value, maintain it for 15 minutes.
6.5.3 Turn on the vacuum pump, vacuumize the pipeline to a gauge pressure below 0.1 MPa,
and introduce helium to replace the gas in the pipeline and the sealed cavity. Repeat this process
twice, and then, turn off the vacuum pump and its pipeline valve.
6.5.4 Open the helium cylinder and introduce the test medium into the sealed cavity. Utilize a
pressure reducing valve to adjust the helium medium pressure to the specified test medium
pressure. Use the helium mass spectrometer to start the leak detection. After 15 minutes, when
the leakage rate value becomes stable, record the leakage rate value.
6.5.5 Close the valve of the helium cylinder, turn off the helium mass spectrometer, release the
helium in the sealed cavity, and stop the test.
6.6 Number of Tests
Select several specimens from the same sample and randomly select no less than 3 specimens
for testing.
6.7 Leakage Rate Calculation and Test Result
The final test result is the arithmetic mean of all calculated values and rounded to two significant
figures.
7 Selection of Test Methods and Precautions
7.1 Based on the leakage rate test range of the three test methods and the estimated leakage rate
range of the test object, select the appropriate test method.
7.2 If the leakage rate range of the test object cannot be estimated, a test method with a large
leakage rate test range may be used for testing first. If necessary, select a test method with a
higher level of leakage rate test range for testing.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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