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Problems existing in the regulations and selection standards of thick-walled steel pipes in engineering

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Thick-walled steel pipes are specified in the project:

Corresponding regulations and various regulations for the practical selection and use of thick-walled pipe fittings. When thick-walled steel pipe and thick-walled pipe fittings are selected or used, they must first follow the corresponding regulations and regulations, especially when transporting extremely or highly hazardous fluids. For pipelines such as combustion medium and high-pressure gas. Under this premise, the type of pipe fittings is mainly determined according to the purpose and use conditions (pressure, temperature, fluid medium). The relevant regulations/norms are listed below for reference only.

1. Special Equipment Supervision Law;

2. List of special equipment inspection regulations;

3. Regulations on the management and supervision of pressure pipelines;

4. Regulations on the supervision and supervision of special equipment;

5. Regulations on the supervision and management of special equipment design/manufacture/installation (draft);

6. Technical supervision regulations for pressure pipelines (to be drawn up);

7. Technical Specifications for Industrial Metal Pipelines (Draft).


Problems existing in the selection standard of thick-walled steel pipes:

1. The standard system is formulated. For the selection in the project, there are pipe standards, but there are no corresponding forgings or casting standards. The reality is that the pipe fittings forgings standard borrows the pressure vessel forgings standard, without considering the difference between the two, such as welding, film inspection, and other regulations.

2. The standard level of pipe fittings varies widely, and the content lacks consistency and systematicness, and even the connection appears contradictory, causing inconvenience in use.

3. There are no type test standards for pipe fittings. Only GB12459 and GB13401 standards stipulate the pressure calculation of the burst test of steel butt welded seamless pipe fittings and steel plate butt welded pipe fittings, and there are no other type test standards or implementation standards to ensure the manufacture of pipe fittings.

Thick-walled seamless pipe weight formula: [(outer diameter-wall thickness)*wall thickness]*0.02466=kg/meter (weight per meter).


Determination of strength grade of thick-walled steel pipe:

1) Pipe fittings whose grade is expressed by nominal pressure or specified pressure-temperature rating should be used as the standard specified pressure-temperature rating, such as GB/T17185;

2) The standard only specifies the nominal thickness of the straight pipe connected to it, and its applicable pressure-temperature rating is determined according to the standard pipe grade specified in the standard, such as GB14383~GB14626.

3) Pipe fittings whose external dimensions are only specified in the standard, such as GB12459 and GB13401, should be confirmed by confirmatory tests to determine their compressive strength.

4) Others, the pressure design or analytical analysis and other methods should be carried out according to the relevant regulations to determine their use benchmarks. In addition, the determination of the strength grade of the pipe fittings should not be lower than the pressure under the severe conditions that the entire piping system may encounter in operation.


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