Flanged Pup Joint Manufacturing Standards

A flanged pup joint is a flange connector that connects pipes and equipment. It usually consists of two flanges and a short connection kit, which is usually a round or square pup joint made of stainless steel or carbon steel.

Core international standards for flanged pup joint manufacturing

As a key component for pipeline connection, the manufacturing of flanged pup joints must comply with the following mainstream standards:

1. ASME B16.5

American Society of Mechanical Engineers standard, applicable to Class 150~2500 pressure levels, specifies the dimensions, tolerances and materials of flanged pup joints (such as ASTM A105 carbon steel). For example, the minimum wall thickness of Class 150 flanged pup joints must be ≥3.2mm (according to ASME B16.5 Table 2-2.1).

2. EN 1092-1

European standard, covering PN6~PN100 pressure systems, requires the bevel angle of the flanged pup joint and the pipeline welding end to be 30°±5° (refer to EN 1092-1 Appendix B).

3. GB/T 9124

Chinese national standard, equivalent to ASME standard but with additional low temperature impact test requirements, Charpy impact energy at -20℃ environment must be ≥27J (according to Article 6.3 of GB/T 9124.1-2019).

Key manufacturing parameters and testing requirements

1. Dimension tolerance control

Flanged pup joint inner diameter deviation: ASME B16.5 allows ±0.8mm (below DN50), GB/T 9124 tightens to ±0.5mm.

Bolt hole center circle diameter tolerance: All standards require ≤±0.6mm (ASME B16.5 Table 4-1).

2. Material and process requirements

Material type Applicable standards Heat treatment requirements

Carbon steel ASTM A105 Normalizing treatment (≥900℃)

Stainless steel ASTM A182 Solution treatment (1010℃~1150℃)

3. Nondestructive testing

Radiographic testing (RT) is in accordance with ASME Section V requirements, and the weld defect acceptance level is ≤2.

Ultrasonic testing (UT) is used for flanged pup joints with a thickness of ≥8mm, and the sensitivity must reach φ3.2mm flat bottom hole (GB/T 5777-2019).

Standard differences and selection recommendations

1. Pressure level conversion

ASME Class 150≈PN20 (EN standard), but the bursting pressure of the PN20 flanged pup joint must be ≥4MPa (ISO 7005-1 verification data).

2. Special environment adaptation

For low temperature working conditions (<-50℃), ASTM A350 LF2 materials should be selected, and the impact energy at -196℃ should be ≥20J (ASME B31.3 Appendix A).

316L stainless steel is recommended for corrosive environments, and the chloride ion tolerance concentration should be ≤2000ppm (NACE MR0175 standard).

From the above analysis, it can be seen that the manufacturing of flanged pup joints must strictly match the application scenarios. The design must comprehensively consider the pressure, temperature and medium characteristics, and give priority to suppliers with third-party certification (such as CE, PED).

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