1 Overview of International Pipe Flange Standard System
There are two main systems for international pipe flange standards:
One is the European pipe flange standard system (ie PN series) represented by the European Union EN, the main standards are EN1092-1, EN 1759 (with reference to the American system).
The other is the American system (ie Class series) represented by ASME in the United States. The main standards are ASME B16.5 and B16.47 (large diameter flanges).
In addition, there is the Japanese JIS system (nominal pressure is expressed by K), but it basically follows the American system.
2 Overview of domestic pipe flange standard system
The current commonly used steel pipe flange standards in China mainly include the national standard GB, the chemical industry standard HG, the machinery industry standard JB and the petrochemical industry standard SH, as shown in the following table.
GB and HG standards cover both European and American systems, and are compiled separately according to the European system and the American system. The context is clear and it is more convenient to use. While the JB and SH standards are applicable to the European system and the American system respectively, the system is relatively single and the scope of application is limited.
Among them, only HG flange has centralized compilation on gasket selection and gasket-fastener selection, and GB, JB, SH have none, and JB, SH fastener selection has no special chapter.
There is no interchangeability and consistency between flange sizes and pressure-temperature grades of different system standards. This requires that the main flange system to be selected should be determined in the design process, and a single flange system should be selected as much as possible, and random mixing may endanger the safety of the entire system.
See the details from the following chart:
3 Some useful conclusions
The paper also draws several conclusions at the end:
1. The EN method is the most advanced in the flange calculation method, but it is more complicated
The internationally recognized scientific calculation method for flanges is the European EN method, which comprehensively considers the stress conditions and various actual working conditions of the entire flange system, and is the most advanced flange design calculation method at present. However, this method has the disadvantage of complicated calculation process.
In addition to this condition, it is recommended to use the ASME method for flange calculation to meet the engineering needs.
2. Current situation of domestic methods
The calculation method of domestic flanges is basically still based on the Walters method. While referring to the American standard ASME, it also absorbs the content of the flange design calculation of the Japanese JIS standard, and the flange strength control index is considered in the calculation. , and the stiffness control index for controlling the flange rotation angle is added, which can currently meet the requirements under general working conditions.
3. The HG system is the most complete, but after the GB is perfected, it will be able to replace HG
Among the domestic flange standards, the most comprehensive standard for the flange system is the chemical industry standard. In its own standard system, the closed-loop selection design of flange selection can be achieved without referring to other standards, and the flange gasket – tight There is a special chapter for the selection of firmware, which is convenient for designers to select.
The compilation rules of the latest version of the national standard for flanges are very similar to those of the chemical industry standard. After the national standard is updated, it can basically replace the chemical industry standard.
4 the SH and JB systems are relatively difficult to use
At present, the parallel situation of domestic flange national standards and industry standards is caused by historical reasons.
The petrochemical industry standard for flanges has only the American Class system, which is currently only used in the original oil refining system and has a limited scope of application; while the industry standard for flange machinery is widely used in the original metallurgy, electric power and other industries, but it only has the European PN system, which is consistent with national standards, chemical industry standards Compared with the comprehensiveness, systematicness and operability of the industry standard, it is not recommended to adopt it.
5. The pressure vessel industry currently prefers HG
The latest version of the flange national standard and chemical industry-standard writing system is complete, and the selection and use are more convenient.
The chemical industry standards are cited by the supervision regulations for pressure vessels and pressure pipelines, and have the effect of mandatory standards. They should be used preferentially in the field of pressure vessels and pressure pipelines.
In the national standard, the flange design selection standard and the calculation method standard correspond one by one, which has the advantage of mutual coordination. It is cited by the supervision regulations of pressure pipelines, so it has a wide range of application prospects in the field of pressure pipeline design.
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