ASME B31.3 Limitations Tubing Joints

ASME B31.3 Limitations Tubing Joints

Tubing joints are covered by para. 315, and include flared, flareless, and compression-type tube fittings. ASME B31.3 provides some listed tubing joints; however, many tubing joints used in process piping are proprietary fittings that are qualified as unlisted components. The following are the listed standards covering tubing joints:

  • SAE J513, Refrigeration Tube Fittings—General Specifications

  • SAE J514, Hydraulic Tube Fittings

These listed components are permitted for use in Normal Fluid Service, provided that they are used within the pressure-temperature limitations of the fittings and joint. They are required to be safeguarded when used under severe cyclic conditions; however, it is highly unlikely that this will occur, because it requires the tube joint to be at over 80% of the allowable displacement stress range. Unlisted tube fittings must be qualified in accordance with para. 304.7.2.

Taper Thread

Minimum Thickness for Threaded Pipe


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